RFC 7518
JSON Web Algorithms (JWA)
RFC 7518: JSON Web Algorithms (JWA) 💖
Okay bestie, let's get into it 🎀. This is RFC 7518, JSON Web Algorithms (JWA), written by M. Jones at Microsoft. It's a Standards Track document from the Internet Engineering Task Force (IETF), dated May 2015, with ISSN 2070-1721 🦋. The title block doesn't list anything it obsoletes or updates, so it doesn't replace or change any earlier RFC 🌸.
Abstract ✨
Okay so this spec registers cryptographic algorithms and identifiers to be used with JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specs. It also defines several IANA registries for these identifiers. It's giving organization, honestly 💅.
Status of This Memo 📜
This is an Internet Standards Track document. 🔥
It's a product of the Internet Engineering Task Force (IETF), and it represents the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). If you want more on Internet Standards, check Section 2 of RFC 5741 💜.
For the current status, any errata, and how to send feedback, go to http://www.rfc-editor.org/info/rfc7518 🌈.
Copyright Notice 🎀
Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved ✨.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as they stand on the publication date. Please read these carefully, bestie, because they spell out your rights and restrictions for this document 🙈. Any Code Components pulled out of this document must include the Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions. They come without warranty, as described in the Simplified BSD License 🫶.
Table of Contents 🗂️
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Cryptographic Algorithms for Digital Signatures and MACs . . 6
3.1. "alg" (Algorithm) Header Parameter Values for JWS . . . . 6
3.2. HMAC with SHA-2 Functions . . . . . . . . . . . . . . . . 7
3.3. Digital Signature with RSASSA-PKCS1-v1_5 . . . . . . . . 8
3.4. Digital Signature with ECDSA . . . . . . . . . . . . . . 9
3.5. Digital Signature with RSASSA-PSS . . . . . . . . . . . . 10
3.6. Using the Algorithm "none" . . . . . . . . . . . . . . . 11
4. Cryptographic Algorithms for Key Management . . . . . . . . . 11
4.1. "alg" (Algorithm) Header Parameter Values for JWE . . . . 12
4.2. Key Encryption with RSAES-PKCS1-v1_5 . . . . . . . . . . 13
4.3. Key Encryption with RSAES OAEP . . . . . . . . . . . . . 14
4.4. Key Wrapping with AES Key Wrap . . . . . . . . . . . . . 14
4.5. Direct Encryption with a Shared Symmetric Key . . . . . . 15
4.6. Key Agreement with Elliptic Curve Diffie-Hellman
Ephemeral Static (ECDH-ES) . . . . . . . . . . . . . . . 15
4.6.1. Header Parameters Used for ECDH Key Agreement . . . . 16
4.6.1.1. "epk" (Ephemeral Public Key) Header Parameter . . 16
4.6.1.2. "apu" (Agreement PartyUInfo) Header Parameter . . 17
4.6.1.3. "apv" (Agreement PartyVInfo) Header Parameter . . 17
4.6.2. Key Derivation for ECDH Key Agreement . . . . . . . . 17
4.7. Key Encryption with AES GCM . . . . . . . . . . . . . . . 18
4.7.1. Header Parameters Used for AES GCM Key Encryption . . 19
4.7.1.1. "iv" (Initialization Vector) Header Parameter . . 19
4.7.1.2. "tag" (Authentication Tag) Header Parameter . . . 19
4.8. Key Encryption with PBES2 . . . . . . . . . . . . . . . . 20
4.8.1. Header Parameters Used for PBES2 Key Encryption . . . 20
4.8.1.1. "p2s" (PBES2 Salt Input) Header Parameter . . . . 21
4.8.1.2. "p2c" (PBES2 Count) Header Parameter . . . . . . 21
5. Cryptographic Algorithms for Content Encryption . . . . . . . 21
5.1. "enc" (Encryption Algorithm) Header Parameter Values for
JWE . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2. AES_CBC_HMAC_SHA2 Algorithms . . . . . . . . . . . . . . 22
5.2.1. Conventions Used in Defining AES_CBC_HMAC_SHA2 . . . 23
5.2.2. Generic AES_CBC_HMAC_SHA2 Algorithm . . . . . . . . . 23
5.2.2.1. AES_CBC_HMAC_SHA2 Encryption . . . . . . . . . . 23
5.2.2.2. AES_CBC_HMAC_SHA2 Decryption . . . . . . . . . . 25
5.2.3. AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . 25
5.2.4. AES_192_CBC_HMAC_SHA_384 . . . . . . . . . . . . . . 26
5.2.5. AES_256_CBC_HMAC_SHA_512 . . . . . . . . . . . . . . 26
5.2.6. Content Encryption with AES_CBC_HMAC_SHA2 . . . . . . 26
5.3. Content Encryption with AES GCM . . . . . . . . . . . . . 27
6. Cryptographic Algorithms for Keys . . . . . . . . . . . . . . 27
6.1. "kty" (Key Type) Parameter Values . . . . . . . . . . . . 28
6.2. Parameters for Elliptic Curve Keys . . . . . . . . . . . 28
6.2.1. Parameters for Elliptic Curve Public Keys . . . . . . 28
6.2.1.1. "crv" (Curve) Parameter . . . . . . . . . . . . . 28
6.2.1.2. "x" (X Coordinate) Parameter . . . . . . . . . . 29
6.2.1.3. "y" (Y Coordinate) Parameter . . . . . . . . . . 29
6.2.2. Parameters for Elliptic Curve Private Keys . . . . . 29
6.2.2.1. "d" (ECC Private Key) Parameter . . . . . . . . . 29
6.3. Parameters for RSA Keys . . . . . . . . . . . . . . . . . 30
6.3.1. Parameters for RSA Public Keys . . . . . . . . . . . 30
6.3.1.1. "n" (Modulus) Parameter . . . . . . . . . . . . . 30
6.3.1.2. "e" (Exponent) Parameter . . . . . . . . . . . . 30
6.3.2. Parameters for RSA Private Keys . . . . . . . . . . . 30
6.3.2.1. "d" (Private Exponent) Parameter . . . . . . . . 30
6.3.2.2. "p" (First Prime Factor) Parameter . . . . . . . 31
6.3.2.3. "q" (Second Prime Factor) Parameter . . . . . . . 31
6.3.2.4. "dp" (First Factor CRT Exponent) Parameter . . . 31
6.3.2.5. "dq" (Second Factor CRT Exponent) Parameter . . . 31
6.3.2.6. "qi" (First CRT Coefficient) Parameter . . . . . 31
6.3.2.7. "oth" (Other Primes Info) Parameter . . . . . . . 31
6.4. Parameters for Symmetric Keys . . . . . . . . . . . . . . 32
6.4.1. "k" (Key Value) Parameter . . . . . . . . . . . . . . 32
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
7.1. JSON Web Signature and Encryption Algorithms Registry . . 33
7.1.1. Registration Template . . . . . . . . . . . . . . . . 34
7.1.2. Initial Registry Contents . . . . . . . . . . . . . . 35
7.2. Header Parameter Names Registration . . . . . . . . . . . 42
7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 42
7.3. JSON Web Encryption Compression Algorithms Registry . . . 43
7.3.1. Registration Template . . . . . . . . . . . . . . . . 43
7.3.2. Initial Registry Contents . . . . . . . . . . . . . . 44
7.4. JSON Web Key Types Registry . . . . . . . . . . . . . . . 44
7.4.1. Registration Template . . . . . . . . . . . . . . . . 44
7.4.2. Initial Registry Contents . . . . . . . . . . . . . . 45
7.5. JSON Web Key Parameters Registration . . . . . . . . . . 45
7.5.1. Registry Contents . . . . . . . . . . . . . . . . . . 46
7.6. JSON Web Key Elliptic Curve Registry . . . . . . . . . . 48
7.6.1. Registration Template . . . . . . . . . . . . . . . . 48
7.6.2. Initial Registry Contents . . . . . . . . . . . . . . 49
8. Security Considerations . . . . . . . . . . . . . . . . . . . 49
8.1. Cryptographic Agility . . . . . . . . . . . . . . . . . . 50
8.2. Key Lifetimes . . . . . . . . . . . . . . . . . . . . . . 50
8.3. RSAES-PKCS1-v1_5 Security Considerations . . . . . . . . 50
8.4. AES GCM Security Considerations . . . . . . . . . . . . . 50
8.5. Unsecured JWS Security Considerations . . . . . . . . . . 51
8.6. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 51
8.7. Reusing Key Material when Encrypting Keys . . . . . . . . 51
8.8. Password Considerations . . . . . . . . . . . . . . . . . 52
8.9. Key Entropy and Random Values . . . . . . . . . . . . . . 52
8.10. Differences between Digital Signatures and MACs . . . . . 52
8.11. Using Matching Algorithm Strengths . . . . . . . . . . . 53
8.12. Adaptive Chosen-Ciphertext Attacks . . . . . . . . . . . 53
8.13. Timing Attacks . . . . . . . . . . . . . . . . . . . . . 53
8.14. RSA Private Key Representations and Blinding . . . . . . 53
9. Internationalization Considerations . . . . . . . . . . . . . 53
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 53
10.1. Normative References . . . . . . . . . . . . . . . . . . 53
10.2. Informative References . . . . . . . . . . . . . . . . . 56
Appendix A. Algorithm Identifier Cross-Reference . . . . . . . . 59
A.1. Digital Signature/MAC Algorithm Identifier Cross-
Reference . . . . . . . . . . . . . . . . . . . . . . . . 60
A.2. Key Management Algorithm Identifier Cross-Reference . . . 61
A.3. Content Encryption Algorithm Identifier Cross-Reference . 62
Appendix B. Test Cases for AES_CBC_HMAC_SHA2 Algorithms . . . . 62
B.1. Test Cases for AES_128_CBC_HMAC_SHA_256 . . . . . . . . . 63
B.2. Test Cases for AES_192_CBC_HMAC_SHA_384 . . . . . . . . . 64
B.3. Test Cases for AES_256_CBC_HMAC_SHA_512 . . . . . . . . . 65
Appendix C. Example ECDH-ES Key Agreement Computation . . . . . 66
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 69
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 691. Introduction 🌸
Okay so this spec registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS) [JWS], JSON Web Encryption (JWE) [JWE], and JSON Web Key (JWK) [JWK] specifications. It defines several IANA registries for these identifiers. All of these specs use JSON-based [RFC7159] data structures, and this one also describes the semantics and operations that are specific to these algorithms and key types 💅.
Why keep the algorithms here instead of in JWS, JWE, and JWK themselves? Bestie, it's so they can stay unchanged even when the set of Required, Recommended, Optional, and Deprecated algorithms shifts over time 🔄. It also means the JWS, JWE, and JWK specs can change without this document needing to change too 🧚.
And yes, the names defined here are short on purpose, because a core goal is for the resulting representations to be compact 🦋✨.
1.1. Notational Conventions ✨
okay bestie, so this part is where we get the ground rules for the whole doc 🎀 the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are supposed to be read the way they're explained in "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119] 💅 and they only count as key words when they're in ALL CAPS 🙈 lowercase "must" is just a regular word, no cap 😭
BASE64URL(OCTETS) is the base64url encoding of OCTETS, per Section 2 of [JWS] 🦋
UTF8(STRING) gives you the octets of the UTF-8 [RFC3629] representation of STRING, where STRING is zero or more Unicode [UNICODE] characters 🌸
ASCII(STRING) gives you the octets of the ASCII [RFC20] representation of STRING, where STRING is zero or more ASCII characters 🧚
and A || B is how we write the concatenation of two values A and B 💜
- Terminology 👑
so the terms "JSON Web Signature (JWS)", "Base64url Encoding", "Header Parameter", "JOSE Header", "JWS Payload", "JWS Protected Header", "JWS Signature", "JWS Signing Input", and "Unsecured JWS" are all defined by the JWS specification [JWS] ✨
the terms "JSON Web Encryption (JWE)", "Additional Authenticated Data (AAD)", "Authentication Tag", "Content Encryption Key (CEK)", "Direct Encryption", "Direct Key Agreement", "JWE Authentication Tag", "JWE Ciphertext", "JWE Encrypted Key", "JWE Initialization Vector", "JWE Protected Header", "Key Agreement with Key Wrapping", "Key Encryption", "Key Management Mode", and "Key Wrapping" come from the JWE specification [JWE] 🎀
"JSON Web Key (JWK)" and "JWK Set" are defined by the JWK specification [JWK] 🫶
"Ciphertext", "Digital Signature", "Initialization Vector", "Message Authentication Code (MAC)", and "Plaintext" are defined by the "Internet Security Glossary, Version 2" [RFC4949] 🌈
and this term is defined right here in this spec, so pay attention 👀
Base64urlUInt 💖 The representation of a positive or zero integer value as the base64url encoding of the value's unsigned big-endian representation as an octet sequence. The octet sequence MUST utilize the minimum number of octets needed to represent the value. Zero is represented as BASE64URL(single zero-valued octet), which is "AA". 🍓
ok so the MUST in there is a hard requirement: use the fewest octets possible, no extra padding octets, and zero is literally just "AA" 💀 iconic energy
- Cryptographic Algorithms for Digital Signatures and MACs 🔥
okay so JWS uses cryptographic algorithms to digitally sign or create a MAC of the contents of the JWS Protected Header and the JWS Payload 🦋
3.1. "alg" (Algorithm) Header Parameter Values for JWS ✨
this table is the set of "alg" (algorithm) Header Parameter values this spec defines for use with JWS, and each one gets explained in more detail in the sections that follow 💅
+--------------+-------------------------------+--------------------+
| "alg" Param | Digital Signature or MAC | Implementation |
| Value | Algorithm | Requirements |
+--------------+-------------------------------+--------------------+
| HS256 | HMAC using SHA-256 | Required |
| HS384 | HMAC using SHA-384 | Optional |
| HS512 | HMAC using SHA-512 | Optional |
| RS256 | RSASSA-PKCS1-v1_5 using | Recommended |
| | SHA-256 | |
| RS384 | RSASSA-PKCS1-v1_5 using | Optional |
| | SHA-384 | |
| RS512 | RSASSA-PKCS1-v1_5 using | Optional |
| | SHA-512 | |
| ES256 | ECDSA using P-256 and SHA-256 | Recommended+ |
| ES384 | ECDSA using P-384 and SHA-384 | Optional |
| ES512 | ECDSA using P-521 and SHA-512 | Optional |
| PS256 | RSASSA-PSS using SHA-256 and | Optional |
| | MGF1 with SHA-256 | |
| PS384 | RSASSA-PSS using SHA-384 and | Optional |
| | MGF1 with SHA-384 | |
| PS512 | RSASSA-PSS using SHA-512 and | Optional |
| | MGF1 with SHA-512 | |
| none | No digital signature or MAC | Optional |
| | performed | |
+--------------+-------------------------------+--------------------+the "+" in the Implementation Requirements column is a little hint that the requirement strength will probably go up in a future version of the spec 👀🔮
see Appendix A.1 for a table that cross-references the JWS digital signature and MAC "alg" (algorithm) values from this spec with the equivalent identifiers used by other standards and software packages 🌸
3.2. HMAC with SHA-2 Functions 🧚
okay so Hash-based Message Authentication Codes (HMACs) let you use a secret plus a cryptographic hash function to generate a MAC 🔐 this can show that whoever generated the MAC had possession of the MAC key 🗝️ the algorithm for implementing and validating HMACs is in RFC 2104 [RFC2104] 💜
A key of the same size as the hash output (for instance, 256 bits for "HS256") or larger MUST be used with this algorithm. (This requirement is based on Section 5.3.4 (Security Effect of the HMAC Key) of NIST SP 800-117 [NIST.800-107], which states that the effective security strength is the minimum of the security strength of the key and two times the size of the internal hash value.) 🚨
ngl this is a big one: your key has to be at least as long as the hash output, so 256 bits for HS256, and the reason is the NIST math where security strength is capped by the smaller of the key and twice the internal hash size 🤓💅
the HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the hash algorithm "H", using the JWS Signing Input as the "text" value, and using the shared key 🎀 the HMAC output value is the JWS Signature ✨
the following "alg" (algorithm) Header Parameter values are used to show that the JWS Signature is an HMAC value computed with the matching algorithm 🦋
+-------------------+--------------------+
| "alg" Param Value | MAC Algorithm |
+-------------------+--------------------+
| HS256 | HMAC using SHA-256 |
| HS384 | HMAC using SHA-384 |
| HS512 | HMAC using SHA-512 |
+-------------------+--------------------+the HMAC SHA-256 MAC for a JWS gets validated by computing an HMAC value per RFC 2104, using SHA-256 as the hash algorithm "H", using the received JWS Signing Input as the "text" value, and using the shared key 🔍 then that computed HMAC value gets compared to the result of base64url decoding the received encoded JWS Signature value 🍓 that comparison MUST be done in a constant-time manner to thwart timing attacks 🛡️⏱️ it's giving security-first, periodt 💅
alternatively, the computed HMAC value can be base64url encoded and compared to the received encoded JWS Signature value (also in a constant-time manner), because that comparison gives the same result as comparing the unencoded values 🌈 either way, if the values match, the HMAC has been validated ✅🎉
securing content and validation with HMAC SHA-384 and HMAC SHA-512 works exactly the same as HMAC SHA-256, just with the corresponding hash algorithms and correspondingly larger minimum key sizes and result values: 384 bits each for HMAC SHA-384 and 512 bits each for HMAC SHA-512 💖
an example using this algorithm is in Appendix A.1 of [JWS] 🫶
3.3. Digital Signature with RSASSA-PKCS1-v1_5 ✨
this section defines the RSASSA-PKCS1-v1_5 digital signature algorithm from Section 8.2 of RFC 3447 [RFC3447] (commonly known as PKCS #1), using SHA-2 [SHS] hash functions 🔐💜
A key of size 2048 bits or larger MUST be used with these algorithms. 🚨
so yeah, your RSA key has to be 2048 bits or bigger, no exceptions 💀
the RSASSA-PKCS1-v1_5 SHA-256 digital signature is generated like this: generate a digital signature of the JWS Signing Input using RSASSA-PKCS1-v1_5-SIGN and the SHA-256 hash function with the desired private key 🦋 that's your JWS Signature value ✨
the following "alg" (algorithm) Header Parameter values are used to show that the JWS Signature is a digital signature value computed with the matching algorithm 🌸
+-------------------+---------------------------------+
| "alg" Param Value | Digital Signature Algorithm |
+-------------------+---------------------------------+
| RS256 | RSASSA-PKCS1-v1_5 using SHA-256 |
| RS384 | RSASSA-PKCS1-v1_5 using SHA-384 |
| RS512 | RSASSA-PKCS1-v1_5 using SHA-512 |
+-------------------+---------------------------------+the RSASSA-PKCS1-v1_5 SHA-256 digital signature for a JWS gets validated like this: submit the JWS Signing Input, the JWS Signature, and the public key that matches the private key the signer used to the RSASSA-PKCS1-v1_5-VERIFY algorithm, using SHA-256 as the hash function 🔎
signing and validation with RSASSA-PKCS1-v1_5 SHA-384 and RSASSA-PKCS1-v1_5 SHA-512 works identically to the RSASSA-PKCS1-v1_5 SHA-256 procedure, just with the corresponding hash algorithms instead of SHA-256 🎀
an example using this algorithm is in Appendix A.2 of [JWS] 💅🌈
3.4. Digital Signature with ECDSA 💖
okay so ECDSA (Elliptic Curve Digital Signature Algorithm) [DSS] lets you use Elliptic Curve Cryptography 🦋 which gives you the same security as RSA but with shorter keys and faster processing for a lot of operations. so ECDSA signatures end up way smaller than RSA signatures that are equally strong. it's giving efficiency ✨
this spec covers ECDSA with P-256 and SHA-256, ECDSA with P-384 and SHA-384, and ECDSA with P-521 and SHA-512. the P-256, P-384, and P-521 curves are defined in [DSS] 💅
here's how the ECDSA P-256 SHA-256 signature gets made 🎀
- Make a signature of the JWS Signing Input using ECDSA P-256 SHA-256 with your private key. The output is a pair (R, S), where R and S are 256-bit unsigned integers.
- Turn R and S into octet sequences in big-endian order, each one 32 octets long. The octet sequences MUST NOT be shortened by dropping any leading zero octets in the values. this part is non-negotiable bestie 🙈
- Glue the two octet sequences together, R first and then S. (Lowkey, a lot of ECDSA implementations already give you this concatenated output directly 🧚)
- The 64-octet result is your JWS Signature value. 🌸
these "alg" (algorithm) Header Parameter values say that the JWS Signature is an ECDSA digital signature made with the matching algorithm 👑
+-------------------+-------------------------------+
| "alg" Param Value | Digital Signature Algorithm |
+-------------------+-------------------------------+
| ES256 | ECDSA using P-256 and SHA-256 |
| ES384 | ECDSA using P-384 and SHA-384 |
| ES512 | ECDSA using P-521 and SHA-512 |
+-------------------+-------------------------------+now the validation for an ECDSA P-256 SHA-256 signature on a JWS 🔍
- The JWS Signature value MUST be a 64-octet sequence. If it isn't 64 octets, the validation has failed. no vibes, just math 💀
- Split that 64-octet sequence into two 32-octet sequences. The first one is R and the second one is S. Turn both into octet sequences using the Integer-to-OctetString Conversion from Section 2.3.7 of SEC1 [SEC1] (in big-endian octet order). ✨
- Hand the JWS Signing Input, R, S, and the public key (x, y) to the ECDSA P-256 SHA-256 validator. 🫶
ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512 work the exact same way as P-256 SHA-256. You just use the matching hash algorithms, and the results are bigger 🌈 For P-384 SHA-384, R and S are each 384 bits, so you get a 96-octet sequence. For P-521 SHA-512, R and S are each 521 bits, so you get a 132-octet sequence. (Okay this is a fun one: the Integer-to-OctetString Conversion from Section 2.3.7 of SEC1 [SEC1] that turns R and S into octets pads the high-order bits with zeros until the size is a multiple of 8. So each 521-bit integer actually takes up 528 bits, which is 66 octets 🙈🍓)
Examples using these algorithms are in Appendices A.3 and A.4 of [JWS]. go look, they're cute 🎀
3.5. Digital Signature with RSASSA-PSS 🌸
this section is about RSASSA-PSS, the digital signature algorithm from Section 8.1 of RFC 3447 [RFC3447]. it uses the MGF1 mask generation function and SHA-2 hash functions 💅 The same hash function is always used for both the RSASSA-PSS hash and the MGF1 hash. The salt is the same size as the hash output. Every other algorithm parameter uses the defaults in Appendix A.2.3 of RFC 3447. ✨
a key of 2048 bits or bigger MUST be used with this algorithm. no tiny keys, periodt 🔥
here's how the RSASSA-PSS SHA-256 signature gets made: make a digital signature of the JWS Signing Input using RSASSA-PSS-SIGN, the SHA-256 hash function, and the MGF1 mask generation function with SHA-256, using your private key. That result is the JWS Signature value. 🦋
these "alg" (algorithm) Header Parameter values say the JWS Signature is an RSASSA-PSS digital signature made with the matching algorithm 👑
+-------------------+-----------------------------------------------+
| "alg" Param Value | Digital Signature Algorithm |
+-------------------+-----------------------------------------------+
| PS256 | RSASSA-PSS using SHA-256 and MGF1 with |
| | SHA-256 |
| PS384 | RSASSA-PSS using SHA-384 and MGF1 with |
| | SHA-384 |
| PS512 | RSASSA-PSS using SHA-512 and MGF1 with |
| | SHA-512 |
+-------------------+-----------------------------------------------+validating an RSASSA-PSS SHA-256 signature on a JWS is pretty chill 🧚 Give the RSASSA-PSS-VERIFY algorithm the JWS Signing Input, the JWS Signature, and the public key that matches the signer's private key. Use SHA-256 as the hash function and MGF1 with SHA-256 as the mask generation function. ✨
RSASSA-PSS SHA-384 and RSASSA-PSS SHA-512 are validated exactly like RSASSA-PSS SHA-256. You just swap in the other hash algorithm for both roles 🌈
3.6. Using the Algorithm "none" 🙈
okay this one is spicy. JWSs MAY also be made without integrity protection. These are called Unsecured JWSs. An Unsecured JWS uses the "alg" value "none" and is formatted just like any other JWS, but it MUST use the empty octet sequence as its JWS Signature value. Recipients MUST verify that the JWS Signature value is the empty octet sequence. 🚨
Implementations that support Unsecured JWSs MUST NOT accept them as valid unless the application says that it's okay for a specific object to not have integrity protection. Implementations MUST NOT accept Unsecured JWSs by default. To help mitigate downgrade attacks, applications MUST NOT turn on acceptance of Unsecured JWSs at a global level, and SHOULD turn it on per object instead. Look at Section 8.5 for the security considerations that come with using this algorithm. Seriously, read it 😭💜
4. Cryptographic Algorithms for Key Management 🔑
JWE uses cryptographic algorithms to encrypt the Content Encryption Key (CEK) or to figure out what it is. 🧚
4.1. "alg" (Algorithm) Header Parameter Values for JWE ✨
okay bestie, this is the big menu 💅 Here's the set of "alg" values this spec defines for JWE. These are the algorithms that encrypt the CEK to make the JWE Encrypted Key, or that use key agreement to agree on the CEK 🔥
+--------------------+--------------------+--------+----------------+
| "alg" Param Value | Key Management | More | Implementation |
| | Algorithm | Header | Requirements |
| | | Params | |
+--------------------+--------------------+--------+----------------+
| RSA1_5 | RSAES-PKCS1-v1_5 | (none) | Recommended- |
| RSA-OAEP | RSAES OAEP using | (none) | Recommended+ |
| | default parameters | | |
| RSA-OAEP-256 | RSAES OAEP using | (none) | Optional |
| | SHA-256 and MGF1 | | |
| | with SHA-256 | | |
| A128KW | AES Key Wrap with | (none) | Recommended |
| | default initial | | |
| | value using | | |
| | 128-bit key | | |
| A192KW | AES Key Wrap with | (none) | Optional |
| | default initial | | |
| | value using | | |
| | 192-bit key | | |
| A256KW | AES Key Wrap with | (none) | Recommended |
| | default initial | | |
| | value using | | |
| | 256-bit key | | |
| dir | Direct use of a | (none) | Recommended |
| | shared symmetric | | |
| | key as the CEK | | |
| ECDH-ES | Elliptic Curve | "epk", | Recommended+ |
| | Diffie-Hellman | "apu", | |
| | Ephemeral Static | "apv" | |
| | key agreement | | |
| | using Concat KDF | | |
| ECDH-ES+A128KW | ECDH-ES using | "epk", | Recommended |
| | Concat KDF and CEK | "apu", | |
| | wrapped with | "apv" | |
| | "A128KW" | | |
| ECDH-ES+A192KW | ECDH-ES using | "epk", | Optional |
| | Concat KDF and CEK | "apu", | |
| | wrapped with | "apv" | |
| | "A192KW" | | |
| ECDH-ES+A256KW | ECDH-ES using | "epk", | Recommended |
| | Concat KDF and CEK | "apu", | |
| | wrapped with | "apv" | |
| | "A256KW" | | |
| A128GCMKW | Key wrapping with | "iv", | Optional |
| | AES GCM using | "tag" | |
| | 128-bit key | | |
| A192GCMKW | Key wrapping with | "iv", | Optional |
| | AES GCM using | "tag" | |
| | 192-bit key | | |
| A256GCMKW | Key wrapping with | "iv", | Optional |
| | AES GCM using | "tag" | |
| | 256-bit key | | |
| PBES2-HS256+A128KW | PBES2 with HMAC | "p2s", | Optional |
| | SHA-256 and | "p2c" | |
| | "A128KW" wrapping | | |
| PBES2-HS384+A192KW | PBES2 with HMAC | "p2s", | Optional |
| | SHA-384 and | "p2c" | |
| | "A192KW" wrapping | | |
| PBES2-HS512+A256KW | PBES2 with HMAC | "p2s", | Optional |
| | SHA-512 and | "p2c" | |
| | "A256KW" wrapping | | |
+--------------------+--------------------+--------+----------------+The More Header Params column shows which extra Header Parameters each algorithm uses, on top of "alg", which they all use. Everything except dir and ECDH-ES also gives you a JWE Encrypted Key value 🦋
The "+" in the Implementation Requirements column means the requirement strength is likely to go up in a future version of the spec. The "-" means it's likely to go down 👀
Heads up: these "+" and "-" marks are only hints about the future. They aren't requirements in themselves.
Want to see how the JWE "alg" values line up with the same identifiers in other standards and software packages? Check out Appendix A.2 🧚
4.2. Key Encryption with RSAES-PKCS1-v1_5
this section is all about encrypting a JWE CEK with RSAES-PKCS1-v1_5 [RFC3447] 🎀 The "alg" value for this one is RSA1_5.
A key of size 2048 bits or larger MUST be used with this algorithm. no shortcuts, bestie 🙅♀️
There's an example of this algorithm in Appendix A.2 of [JWE] 🌸
4.3. Key Encryption with RSAES OAEP
this section covers encrypting a JWE CEK with RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447] ✨ There are two parameter sets for OAEP, and they use different hash functions. In the first case, you use the default parameters from Appendix A.2.1 of RFC 3447. (Those defaults are the SHA-1 hash function and the MGF1 with SHA-1 mask generation function.) In the second case, you use the SHA-256 hash function and the MGF1 with SHA-256 mask generation function 🍓
These "alg" values tell you the JWE Encrypted Key came from encrypting the CEK with the matching algorithm:
+-------------------+-----------------------------------------------+
| "alg" Param Value | Key Management Algorithm |
+-------------------+-----------------------------------------------+
| RSA-OAEP | RSAES OAEP using default parameters |
| RSA-OAEP-256 | RSAES OAEP using SHA-256 and MGF1 with |
| | SHA-256 |
+-------------------+-----------------------------------------------+A key of size 2048 bits or larger MUST be used with these algorithms. (This comes from Table 4 (Security-strength time frames) of NIST SP 800-57 [NIST.800-57], which asks for 112 bits of security for new uses, plus Table 2 (Comparable strengths) of the same doc, which says 2048-bit RSA keys give you 112 bits of security. the math is mathing 🧮)
There's an example using RSAES OAEP with the default parameters in Appendix A.1 of [JWE] 💖
4.4. Key Wrapping with AES Key Wrap
this section defines how to encrypt a JWE CEK with the Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394], using the default initial value from Section 2.2.3.1 of that document 🫶
These "alg" values say the JWE Encrypted Key is the CEK encrypted with the matching algorithm and key size:
+-----------------+-------------------------------------------------+
| "alg" Param | Key Management Algorithm |
| Value | |
+-----------------+-------------------------------------------------+
| A128KW | AES Key Wrap with default initial value using |
| | 128-bit key |
| A192KW | AES Key Wrap with default initial value using |
| | 192-bit key |
| A256KW | AES Key Wrap with default initial value using |
| | 256-bit key |
+-----------------+-------------------------------------------------+There's an example of this algorithm in Appendix A.3 of [JWE] 🦋
4.5. Direct Encryption with a Shared Symmetric Key
this section is for doing symmetric encryption directly, skipping the key wrapping step 🌈 The shared symmetric key gets used as is for the CEK for the "enc" algorithm. The JWE Encrypted Key value is an empty octet sequence, and the "alg" value is dir 💜
Before you go direct, read the security considerations on key lifetimes in Section 8.2 and on AES GCM in Section 8.4. Trust me, you want to know what they say first 😭
4.6. Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral Static (ECDH-ES)
this section covers key agreement with Elliptic Curve Diffie-Hellman Ephemeral Static [RFC6090], combined with the Concat KDF from Section 5.8.1 of [NIST.800-56A] 🧚 The key agreement result can be used in one of two ways:
- directly as the Content Encryption Key (CEK) for the
"enc"algorithm, in the Direct Key Agreement mode, or - as a symmetric key used to wrap the CEK with the
"A128KW","A192KW", or"A256KW"algorithms, in the Key Agreement with Key Wrapping mode.
A new ephemeral public key value MUST be generated for each key agreement operation. every single time, no reusing 🙅♀️✨
In Direct Key Agreement mode, the output of the Concat KDF MUST be a key of the same length as the one the "enc" algorithm uses. In this case, the empty octet sequence is the JWE Encrypted Key value. The "alg" value ECDH-ES is what you use for Direct Key Agreement mode 🔥
In Key Agreement with Key Wrapping mode, the output of the Concat KDF MUST be a key of the length the chosen key wrapping algorithm needs. In this case, the JWE Encrypted Key is the CEK wrapped with the agreed-upon key 🎀
These "alg" values say the JWE Encrypted Key is the CEK encrypted with the key agreement result used as the key encryption key for the matching key wrapping algorithm:
+-----------------+-------------------------------------------------+
| "alg" Param | Key Management Algorithm |
| Value | |
+-----------------+-------------------------------------------------+
| ECDH-ES+A128KW | ECDH-ES using Concat KDF and CEK wrapped with |
| | "A128KW" |
| ECDH-ES+A192KW | ECDH-ES using Concat KDF and CEK wrapped with |
| | "A192KW" |
| ECDH-ES+A256KW | ECDH-ES using Concat KDF and CEK wrapped with |
| | "A256KW" |
+-----------------+-------------------------------------------------+4.6.1. Header Parameters Used for ECDH Key Agreement 🦋
okay so these are the Header Parameter names you use for key agreement. Here's the lineup 💖
4.6.1.1. "epk" (Ephemeral Public Key) Header Parameter ✨
the epk is the ephemeral public key the originator creates for key agreement algorithms. It's represented as a JSON Web Key [JWK] public key value. It MUST contain only public key parameters, and it SHOULD contain only the minimum JWK parameters needed to represent the key. Any other JWK parameters that show up can be checked for consistency and honored, or they can be ignored 💅 This Header Parameter MUST be present, and it MUST be understood and processed by implementations whenever these algorithms are used. no skipping it 😭
4.6.1.2. "apu" (Agreement PartyUInfo) Header Parameter 🌸
the apu is the PartyUInfo value for key agreement algorithms that use it (like "ECDH-ES"), and it's represented as a base64url-encoded string. When it's used, PartyUInfo holds information about the producer. Use of this Header Parameter is OPTIONAL 🫶 but when it's used, it MUST be understood and processed by implementations when these algorithms are used.
4.6.1.3. "apv" (Agreement PartyVInfo) Header Parameter 🍓
the apv is the PartyVInfo value for key agreement algorithms that use it (like "ECDH-ES"), represented as a base64url encoded string. When it's used, PartyVInfo holds information about the recipient. Use of this Header Parameter is OPTIONAL. This Header Parameter MUST be understood and processed by implementations when these algorithms are used. main character energy 👑
4.6.2. Key Derivation for ECDH Key Agreement 🧚
okay so key derivation takes the agreed-upon key out of the shared secret Z that ECDH establishes, following Section 6.2.2.2 of [NIST.800-56A].
Key derivation uses the Concat KDF from Section 5.8.1 of [NIST.800-56A], where the Digest Method is SHA-256. The Concat KDF parameters get set up like this:
Z: This is set to the representation of the shared secret Z as an octet sequence.keydatalen: This is set to the number of bits in the desired output key. For"ECDH-ES", this is the length of the key used by theencalgorithm. For"ECDH-ES+A128KW","ECDH-ES+A192KW", and"ECDH-ES+A256KW", this is 128, 192, and 256, respectively.AlgorithmID: The AlgorithmID value is of the formDatalen || Data, whereDatais a variable-length string of zero or more octets, andDatalenis a fixed-length, big-endian 32-bit counter that indicates the length (in octets) ofData. In the Direct Key Agreement case,Datais set to the octets of the ASCII representation of the"enc"Header Parameter value. In the Key Agreement with Key Wrapping case,Datais set to the octets of the ASCII representation of the"alg"(algorithm) Header Parameter value.PartyUInfo: The PartyUInfo value is of the formDatalen || Data, whereDatais a variable-length string of zero or more octets, andDatalenis a fixed-length, big-endian 32-bit counter that indicates the length (in octets) ofData. If an"apu"(agreement PartyUInfo) Header Parameter is present,Datais set to the result of base64url decoding the"apu"value andDatalenis set to the number of octets inData. Otherwise,Datalenis set to 0 andDatais set to the empty octet sequence.PartyVInfo: The PartyVInfo value is of the formDatalen || Data, whereDatais a variable-length string of zero or more octets, andDatalenis a fixed-length, big-endian 32-bit counter that indicates the length (in octets) ofData. If an"apv"(agreement PartyVInfo) Header Parameter is present,Datais set to the result of base64url decoding the"apv"value andDatalenis set to the number of octets inData. Otherwise,Datalenis set to 0 andDatais set to the empty octet sequence.SuppPubInfo: This is set to thekeydatalenrepresented as a 32-bit big-endian integer.SuppPrivInfo: This is set to the empty octet sequence.
Applications need to decide how the apu and apv Header Parameters get used for that application. The apu and apv values MUST be distinct, when used. Applications that want to conform to [NIST.800-56A] need to provide values that meet the requirements of that document, e.g., by using values that identify the producer and consumer. Alternatively, applications MAY conduct key derivation in a manner similar to "Diffie-Hellman Key Agreement Method" [RFC2631]. In that case, the apu parameter MAY either be omitted or represent a random 512-bit value (analogous to PartyAInfo in Ephemeral-Static mode in RFC 2631), and the apv parameter SHOULD NOT be present.
See Appendix C for an example key agreement computation using this method 🌈
4.7. Key Encryption with AES GCM 🎀
this section is all about encrypting a JWE Content Encryption Key (CEK) with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) ([AES] and [NIST.800-38D]).
Use of an Initialization Vector (IV) of size 96 bits is REQUIRED with this algorithm. The IV is represented in base64url-encoded form as the "iv" (initialization vector) Header Parameter value.
The Additional Authenticated Data value used is the empty octet string.
The requested size of the Authentication Tag output MUST be 128 bits, regardless of the key size.
The JWE Encrypted Key value is the ciphertext output.
The Authentication Tag output is represented in base64url-encoded form as the "tag" (authentication tag) Header Parameter value.
The following "alg" (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the corresponding algorithm and key size:
+-------------------+---------------------------------------------+
| "alg" Param Value | Key Management Algorithm |
+-------------------+---------------------------------------------+
| A128GCMKW | Key wrapping with AES GCM using 128-bit key |
| A192GCMKW | Key wrapping with AES GCM using 192-bit key |
| A256GCMKW | Key wrapping with AES GCM using 256-bit key |
+-------------------+---------------------------------------------+4.7.1. Header Parameters Used for AES GCM Key Encryption 🧁
the following Header Parameters are used for AES GCM key encryption.
4.7.1.1. "iv" (Initialization Vector) Header Parameter 💜
the "iv" (initialization vector) Header Parameter value is the base64url-encoded representation of the 96-bit IV value used for the key encryption operation. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
4.7.1.2. "tag" (Authentication Tag) Header Parameter 🔥
the "tag" (authentication tag) Header Parameter value is the base64url-encoded representation of the 128-bit Authentication Tag value that comes out of the key encryption operation. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
4.8. Key Encryption with PBES2 🔐
this section covers password-based encryption of a JWE CEK. First you derive a key encryption key from a user-supplied password using PBES2 schemes, as specified in Section 6.2 of [RFC2898], and then you encrypt the JWE CEK with that derived key.
These algorithms use HMAC SHA-2 algorithms as the Pseudorandom Function (PRF) for the PBKDF2 key derivation, and AES Key Wrap [RFC3394] for the encryption scheme. The PBES2 password input is an octet sequence. If the password is represented as a text string rather than an octet sequence, the UTF-8 encoding of the text string MUST be used as the octet sequence. The salt parameter MUST be computed from the "p2s" (PBES2 salt input) Header Parameter value and the "alg" (algorithm) Header Parameter value, as specified in the "p2s" definition below. The iteration count parameter MUST be provided as the "p2c" (PBES2 count) Header Parameter value. The algorithms respectively use HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 as the PRF, and they use 128-, 192-, and 256-bit AES Key Wrap keys. Their derived-key lengths are 16, 24, and 32 octets, respectively.
The following "alg" (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the result of the corresponding password-based encryption algorithm as the key encryption key for the corresponding key wrapping algorithm:
+--------------------+----------------------------------------------+
| "alg" Param Value | Key Management Algorithm |
+--------------------+----------------------------------------------+
| PBES2-HS256+A128KW | PBES2 with HMAC SHA-256 and "A128KW" |
| | wrapping |
| PBES2-HS384+A192KW | PBES2 with HMAC SHA-384 and "A192KW" |
| | wrapping |
| PBES2-HS512+A256KW | PBES2 with HMAC SHA-512 and "A256KW" |
| | wrapping |
+--------------------+----------------------------------------------+See Appendix C of the JWK specification [JWK] for an example key encryption computation using "PBES2-HS256+A128KW".
4.8.1. Header Parameters Used for PBES2 Key Encryption 🌷
the following Header Parameters are used for Key Encryption with PBES2.
4.8.1.1. "p2s" (PBES2 Salt Input) Header Parameter 🦄
the "p2s" (PBES2 salt input) Header Parameter encodes a Salt Input value, which is used as part of the PBKDF2 salt value. The "p2s" value is BASE64URL(Salt Input). This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
the salt expands the possible keys that can be derived from a given password. A Salt Input value containing 8 or more octets MUST be used. A new Salt Input value MUST be generated randomly for every encryption operation. See RFC 4086 [RFC4086] for considerations on generating random values. The salt value used is (UTF8(Alg) || 0x00 || Salt Input), where Alg is the "alg" (algorithm) Header Parameter value.
4.8.1.2. "p2c" (PBES2 Count) Header Parameter 🍬
the "p2c" (PBES2 count) Header Parameter contains the PBKDF2 iteration count, represented as a positive JSON integer. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
the iteration count adds computational expense, ideally compounded by the possible range of keys introduced by the salt. A minimum iteration count of 1000 is RECOMMENDED. 💅
5. Cryptographic Algorithms for Content Encryption 💖
JWE uses cryptographic algorithms to encrypt and integrity-protect the plaintext, and to integrity-protect the Additional Authenticated Data. ✨
5.1. "enc" (Encryption Algorithm) Header Parameter Values for JWE 🎀
Okay bestie, here's the full menu of enc (encryption algorithm) Header Parameter values this spec defines for JWE. The Implementation Requirements column tells you who's needed and who's optional 💅
+---------------+----------------------------------+----------------+
| "enc" Param | Content Encryption Algorithm | Implementation |
| Value | | Requirements |
+---------------+----------------------------------+----------------+
| A128CBC-HS256 | AES_128_CBC_HMAC_SHA_256 | Required |
| | authenticated encryption | |
| | algorithm, as defined in Section | |
| | 5.2.3 | |
| A192CBC-HS384 | AES_192_CBC_HMAC_SHA_384 | Optional |
| | authenticated encryption | |
| | algorithm, as defined in Section | |
| | 5.2.4 | |
| A256CBC-HS512 | AES_256_CBC_HMAC_SHA_512 | Required |
| | authenticated encryption | |
| | algorithm, as defined in Section | |
| | 5.2.5 | |
| A128GCM | AES GCM using 128-bit key | Recommended |
| A192GCM | AES GCM using 192-bit key | Optional |
| A256GCM | AES GCM using 256-bit key | Recommended |
+---------------+----------------------------------+----------------+Every single one of these also uses a JWE Initialization Vector value and produces JWE Ciphertext and JWE Authentication Tag values. 🦋
Want to see how these match up with the names other standards and software packages use? Check out Appendix A.3 🧚
5.2. AES_CBC_HMAC_SHA2 Algorithms 🌸
This section is giving "whole family energy." It defines a family of authenticated encryption algorithms built by combining AES [AES] in Cipher Block Chaining (CBC) mode [NIST.800-38A], with PKCS #7 padding per Section 6.3 of [RFC5652], and HMAC ([RFC2104] and [SHS]) operations. The family is called AES_CBC_HMAC_SHA2, and it has three instances: one with 128-bit CBC keys and HMAC SHA-256, one with 192-bit CBC keys and HMAC SHA-384, and one with 256-bit CBC keys and HMAC SHA-512. Test cases for all of these are in Appendix B 🧪
These algorithms are based on "Authenticated Encryption with AES-CBC and HMAC-SHA" [AEAD-CBC-SHA]. They do the exact same cryptographic computations, but the Initialization Vector (IV) and Authentication Tag values stay separate instead of being glued onto the ciphertext in the output. That option is talked about in Appendix B of that spec. This family is a generalization of the one in [AEAD-CBC-SHA], so it can be used to implement those algorithms too 🫶
5.2.1. Conventions Used in Defining AES_CBC_HMAC_SHA2 📝
Here's the notation we're using, and it's simpler than it looks:
CBC-PKCS7-ENC(X, P) denotes the AES-CBC encryption of P using PKCS
#7 padding utilizing the cipher with the key X.
MAC(Y, M) denotes the application of the MAC to the message M
using the key Y.5.2.2. Generic AES_CBC_HMAC_SHA2 Algorithm 💖
This part defines AES_CBC_HMAC_SHA2 in a way that doesn't care about the AES-CBC key size or which hash function gets used. Sections 5.2.2.1 and 5.2.2.2 cover the generic encryption and decryption algorithms. Sections 5.2.3 through 5.2.5 are the instances that fill in those details ✨
5.2.2.1. AES_CBC_HMAC_SHA2 Encryption 🔐
The authenticated encryption algorithm takes in four octet strings: a secret key K, a plaintext P, Additional Authenticated Data A, and an Initialization Vector IV. It gives back the authenticated ciphertext value E and the Authentication Tag value T. The plaintext gets encrypted and authenticated, while the Additional Authenticated Data gets authenticated but not encrypted.
The encryption process goes like this, or you can use an equivalent set of steps:
- The secondary keys
MAC_KEYandENC_KEYare generated from the input key K as follows. Each of these two keys is an octet string.MAC_KEYconsists of the initialMAC_KEY_LENoctets of K, in order.ENC_KEYconsists of the finalENC_KEY_LENoctets of K, in order.
The number of octets in the input key K MUST be the sum of MAC_KEY_LEN and ENC_KEY_LEN. The values of these parameters are specified by the Authenticated Encryption algorithms in Sections 5.2.3 through 5.2.5. Note that the MAC key comes before the encryption key in the input key K. This is the opposite order of the algorithm names in the identifier "AES_CBC_HMAC_SHA2", so don't mix them up 👀
- The IV used is a 128-bit value generated randomly or pseudorandomly for use in the cipher.
- The plaintext is CBC encrypted using PKCS #7 padding using
ENC_KEYas the key and the IV. We denote the ciphertext output from this step as E. - The octet string AL is equal to the number of bits in the Additional Authenticated Data A expressed as a 64-bit unsigned big-endian integer.
- A message Authentication Tag T is computed by applying HMAC [RFC2104] to the following data, in order:
- the Additional Authenticated Data A,
- the Initialization Vector IV,
- the ciphertext E computed in the previous step, and
- the octet string AL defined above.
The string MAC_KEY is used as the MAC key. We denote the output of the MAC computed in this step as M. The first T_LEN octets of M are used as T.
- The ciphertext E and the Authentication Tag T are returned as the outputs of the authenticated encryption.
Here's the whole encryption process in one picture. K, P, A, IV, and E stand for the key, plaintext, Additional Authenticated Data, Initialization Vector, and ciphertext 🦋
MAC_KEY = initial MAC_KEY_LEN octets of K,
ENC_KEY = final ENC_KEY_LEN octets of K,
E = CBC-PKCS7-ENC(ENC_KEY, P),
M = MAC(MAC_KEY, A || IV || E || AL),
T = initial T_LEN octets of M.5.2.2.2. AES_CBC_HMAC_SHA2 Decryption 🔓
The authenticated decryption operation has five inputs: K, A, IV, E, and T, as defined above. It has only one output: either a plaintext value P, or a special symbol FAIL that says the inputs aren't authentic. Here's the flow, or an equivalent set of steps:
- The secondary keys
MAC_KEYandENC_KEYare generated from the input key K as in Step 1 of Section 5.2.2.1. - The integrity and authenticity of A and E are checked by computing an HMAC with the inputs as in Step 5 of Section 5.2.2.1. The value T, from the previous step, is compared to the first
MAC_KEYlength bits of the HMAC output. If those values are identical, then A and E are considered valid, and processing is continued. Otherwise, all of the data used in the MAC validation are discarded, and the authenticated decryption operation returns an indication that it failed, and the operation halts. (But see Section 11.5 of [JWE] for security considerations on thwarting timing attacks.)
Heads up, the timing attack stuff is in Section 11.5 of [JWE], so go read that one 🙈
- The value E is decrypted and the PKCS #7 padding is checked and removed. The value IV is used as the Initialization Vector. The value
ENC_KEYis used as the decryption key. - The plaintext value is returned.
5.2.3. AES_128_CBC_HMAC_SHA_256 🌷
This algorithm is a concrete version of the generic AES_CBC_HMAC_SHA2 algorithm above. It uses the HMAC message authentication code [RFC2104] with the SHA-256 hash function [SHS] to provide message authentication. The HMAC output gets truncated to 128 bits, which matches the HMAC-SHA-256-128 algorithm defined in [RFC4868]. For encryption, it uses AES in CBC mode as defined in Section 6.2 of [NIST.800-38A], with PKCS #7 padding and a 128-bit IV value.
The AES_CBC_HMAC_SHA2 parameters specific to AES_128_CBC_HMAC_SHA_256 are:
- The input key K is 32 octets long.
ENC_KEY_LENis 16 octets.MAC_KEY_LENis 16 octets.- The SHA-256 hash algorithm is used for the HMAC.
- The HMAC-SHA-256 output is truncated to
T_LEN=16octets, by stripping off the final 16 octets.
5.2.4. AES_192_CBC_HMAC_SHA_384 🍓
AES_192_CBC_HMAC_SHA_384 is based on AES_128_CBC_HMAC_SHA_256, but with these differences:
- The input key K is 48 octets long instead of 32.
ENC_KEY_LENis 24 octets instead of 16.MAC_KEY_LENis 24 octets instead of 16.- SHA-384 is used for the HMAC instead of SHA-256.
- The HMAC SHA-384 value is truncated to
T_LEN=24octets instead of 16.
5.2.5. AES_256_CBC_HMAC_SHA_512 👑
AES_256_CBC_HMAC_SHA_512 is based on AES_128_CBC_HMAC_SHA_256, but with these differences:
- The input key K is 64 octets long instead of 32.
ENC_KEY_LENis 32 octets instead of 16.MAC_KEY_LENis 32 octets instead of 16.- SHA-512 is used for the HMAC instead of SHA-256.
- The HMAC SHA-512 value is truncated to
T_LEN=32octets instead of 16.
5.2.6. Content Encryption with AES_CBC_HMAC_SHA2 💜
This section gets into the specifics of doing authenticated encryption with the AES_CBC_HMAC_SHA2 algorithms.
The CEK is used as the secret key K.
These "enc" (encryption algorithm) Header Parameter values tell you that the JWE Ciphertext and JWE Authentication Tag values were computed with the matching algorithm:
+---------------+---------------------------------------------------+
| "enc" Param | Content Encryption Algorithm |
| Value | |
+---------------+---------------------------------------------------+
| A128CBC-HS256 | AES_128_CBC_HMAC_SHA_256 authenticated encryption |
| | algorithm, as defined in Section 5.2.3 |
| A192CBC-HS384 | AES_192_CBC_HMAC_SHA_384 authenticated encryption |
| | algorithm, as defined in Section 5.2.4 |
| A256CBC-HS512 | AES_256_CBC_HMAC_SHA_512 authenticated encryption |
| | algorithm, as defined in Section 5.2.5 |
+---------------+---------------------------------------------------+5.3. Content Encryption with AES GCM 🎀
Okay bestie, this part is all about doing authenticated encryption with AES in Galois/Counter Mode (GCM) ([AES] and [NIST.800-38D]) 🔐✨
The CEK is used as the encryption key 🗝️
Use of an IV of size 96 bits is REQUIRED with this algorithm 💅
The requested size of the Authentication Tag output MUST be 128 bits, regardless of the key size. No exceptions, no drama 🫶
The enc (encryption algorithm) Header Parameter values below tell you the JWE Ciphertext and JWE Authentication Tag were computed with the matching algorithm and key size 🦋
+-------------------+------------------------------+
| "enc" Param Value | Content Encryption Algorithm |
+-------------------+------------------------------+
| A128GCM | AES GCM using 128-bit key |
| A192GCM | AES GCM using 192-bit key |
| A256GCM | AES GCM using 256-bit key |
+-------------------+------------------------------+There's a full example of this algorithm in Appendix A.1 of [JWE] 🧚
6. Cryptographic Algorithms for Keys 🦋
Okay so a JSON Web Key (JWK) [JWK] is a JSON data structure that represents a cryptographic key 🔑 These keys can be asymmetric or symmetric, and they can hold both public and private info about the key 👀 This section defines the parameters for keys using the algorithms specified by this document 💖
6.1. "kty" (Key Type) Parameter Values 💜
This table is the full set of "kty" (key type) parameter values this specification defines for use in JWKs 📋
+-------------+--------------------------------+--------------------+
| "kty" Param | Key Type | Implementation |
| Value | | Requirements |
+-------------+--------------------------------+--------------------+
| EC | Elliptic Curve [DSS] | Recommended+ |
| RSA | RSA [RFC3447] | Required |
| oct | Octet sequence (used to | Required |
| | represent symmetric keys) | |
+-------------+--------------------------------+--------------------+The "+" in the Implementation Requirements column is a little hint that the requirement strength will probably go up in a future version of the spec 👀🌸
6.2. Parameters for Elliptic Curve Keys 🌈
JWKs can represent Elliptic Curve [DSS] keys. When they do, the "kty" member value is "EC" 💅
6.2.1. Parameters for Elliptic Curve Public Keys 🍓
An Elliptic Curve public key is a pair of coordinates drawn from a finite field, and together they define a point on an Elliptic Curve 🧚 The following members MUST be present for all Elliptic Curve public keys:
"crv""x"
The following member MUST also be present for Elliptic Curve public keys on the three curves in the next section:
"y"
6.2.1.1. "crv" (Curve) Parameter 🌸
The "crv" (curve) parameter identifies the cryptographic curve used with the key. The curve values from [DSS] that this spec uses are:
"P-256""P-384""P-521"
These values are registered in the IANA "JSON Web Key Elliptic Curve" registry defined in Section 7.6. Other specs can register extra "crv" values too 🫶 Anyone registering additional curves must define which parameters represent keys for those curves. The "crv" value is a case-sensitive string, so be careful with your capitals 🙈
SEC1 [SEC1] point compression is not supported for any of these three curves 🚫
6.2.1.2. "x" (X Coordinate) Parameter 🦋
The "x" (x coordinate) parameter holds the x coordinate for the Elliptic Curve point. It's stored as the base64url encoding of the octet string representation of the coordinate, as defined in Section 2.3.5 of SEC1 [SEC1] ✨ The length of this octet string MUST be the full size of a coordinate for the curve named in the "crv" parameter. For example, if "crv" is "P-521", the octet string must be 66 octets long 💅
6.2.1.3. "y" (Y Coordinate) Parameter 🌈
The "y" (y coordinate) parameter holds the y coordinate for the Elliptic Curve point. It's stored as the base64url encoding of the octet string representation of the coordinate, as defined in Section 2.3.5 of SEC1 [SEC1] 💖 The length of this octet string MUST be the full size of a coordinate for the curve named in the "crv" parameter. For example, if "crv" is "P-521", the octet string must be 66 octets long 🔥
6.2.2. Parameters for Elliptic Curve Private Keys 🔐
On top of the members used for Elliptic Curve public keys, the following member MUST be present to represent Elliptic Curve private keys 🗝️
6.2.2.1. "d" (ECC Private Key) Parameter 🌙
The "d" (ECC private key) parameter holds the Elliptic Curve private key value. It's stored as the base64url encoding of the octet string representation of the private key value, as defined in Section 2.3.7 of SEC1 [SEC1]. The length of this octet string MUST be ceiling(log-base-2(n)/8) octets, where n is the order of the curve 🧮
6.3. Parameters for RSA Keys 💜
JWKs can represent RSA [RFC3447] keys. In that case, the "kty" member value is "RSA". The parameters below have the same semantics as the ones in Sections 3.1 and 3.2 of RFC 3447 🎀
6.3.1. Parameters for RSA Public Keys 🦋
The following members MUST be present for RSA public keys 📋
6.3.1.1. "n" (Modulus) Parameter 🌸
The "n" (modulus) parameter holds the modulus value for the RSA public key. It's represented as a Base64urlUInt-encoded value.
Heads up: implementers have found that some cryptographic libraries stick an extra zero-valued octet onto the modulus representations they return. For example, they hand back 257 octets for a 2048-bit key instead of 256. Implementations using those libraries will need to take care to omit the extra octet from the base64url-encoded representation 🙈
6.3.1.2. "e" (Exponent) Parameter 🍓
The "e" (exponent) parameter holds the exponent value for the RSA public key. It's represented as a Base64urlUInt-encoded value 💅
For instance, when representing the value 65537, the octet sequence to be base64url-encoded MUST consist of the three octets [1, 0, 1]. The resulting representation for this value is "AQAB" ✨
6.3.2. Parameters for RSA Private Keys 🔐
On top of the members used for RSA public keys, the following members represent RSA private keys. The "d" parameter is REQUIRED for RSA private keys. The others enable optimizations and SHOULD be included by producers of JWKs representing RSA private keys. If the producer includes any of the other private key parameters, then all of the others MUST be present, except for "oth", which MUST only be present when more than two prime factors were used 🫶
6.3.2.1. "d" (Private Exponent) Parameter 🌈
The "d" (private exponent) parameter holds the private exponent value for the RSA private key. It's represented as a Base64urlUInt-encoded value 🔑
6.3.2.2. "p" (First Prime Factor) Parameter 💖
The "p" (first prime factor) parameter holds the first prime factor. It's represented as a Base64urlUInt-encoded value ✨
6.3.2.3. "q" (Second Prime Factor) Parameter 🌸
The "q" (second prime factor) parameter holds the second prime factor. It's represented as a Base64urlUInt-encoded value 🦋
6.3.2.4. "dp" (First Factor CRT Exponent) Parameter 🧚
The "dp" (first factor CRT exponent) parameter holds the Chinese Remainder Theorem (CRT) exponent of the first factor. It's represented as a Base64urlUInt-encoded value 🧮
6.3.2.5. "dq" (Second Factor CRT Exponent) Parameter 🍓
The "dq" (second factor CRT exponent) parameter holds the CRT exponent of the second factor. It's represented as a Base64urlUInt-encoded value 💅
6.3.2.6. "qi" (First CRT Coefficient) Parameter 👑
The "qi" (first CRT coefficient) parameter holds the CRT coefficient of the second factor. It's represented as a Base64urlUInt-encoded value 💜
6.3.2.7. "oth" (Other Primes Info) Parameter 🌈
The "oth" (other primes info) parameter holds an array of info about any third and subsequent primes, should they exist. When only two primes have been used (the normal case), this parameter MUST be omitted. When three or more primes have been used, the number of array elements MUST be the number of primes used minus two. For more on this case, check out the description of the OtherPrimeInfo parameters in Appendix A.1.2 of RFC 3447 [RFC3447], which the following parameters are modeled on 🎀
If the consumer of a JWK doesn't support private keys with more than two primes and it runs into a private key that includes the "oth" parameter, then it MUST NOT use the key. 🚫 Each array element MUST be an object with the following members.
6.3.2.7.1. "r" (Prime Factor) 🦋
The "r" (prime factor) parameter inside an "oth" array member represents the value of a subsequent prime factor. It's represented as a Base64urlUInt-encoded value ✨
6.3.2.7.2. "d" (Factor CRT Exponent) 🌸
The "d" (factor CRT exponent) parameter inside an "oth" array member represents the CRT exponent of the matching prime factor. It's represented as a Base64urlUInt-encoded value 🧮
6.3.2.7.3. "t" (Factor CRT Coefficient) 💖
The "t" (factor CRT coefficient) parameter inside an "oth" array member represents the CRT coefficient of the matching prime factor. It's represented as a Base64urlUInt-encoded value 🌈
6.4. Parameters for Symmetric Keys 🔑
When the JWK "kty" member value is "oct" (octet sequence), the member "k" (see Section 6.4.1) represents a symmetric key, or another key whose value is a single octet sequence 🫶 An "alg" member SHOULD also be present to identify the algorithm meant to be used with the key, unless the application uses another means or convention to figure out the algorithm 💅
6.4.1. "k" (Key Value) Parameter 🍓
The "k" (key value) parameter holds the value of the symmetric (or other single-valued) key. It's represented as the base64url encoding of the octet sequence containing the key value ✨
7. IANA Considerations ✨
okay bestie, this section is all about how new values get added to the registries this spec sets up 📋 and the rule is the same for every single one 💅
The registration procedure for values is Specification Required [RFC5226] after a three-week review period on the jose-reg-review@ietf.org mailing list 📬, and it happens on the advice of one or more Designated Experts 🧠. Here's the tea though: so values can be allocated before publication, the Designated Experts are allowed to approve a registration once they're satisfied that the spec will be published 🔮.
Registration requests sent to that list for review should use an appropriate subject, like Request to register algorithm: example 💌.
During the review period, the Designated Experts will either approve or deny the request and tell the review list and IANA about it 📣. Denials should come with an explanation and, if it applies, suggestions for how to make the request work 🙏.
If a request is still undetermined after a period longer than 21 days, it can be brought to the IESG's attention (using the iesg@ietf.org mailing list) for resolution 😤.
The criteria the Designated Experts apply are: whether the registration duplicates existing functionality, whether it's likely to be of general applicability or only useful for a single application, and whether the registration description is clear ✅.
IANA must only accept registry updates from the Designated Experts and should direct all registration requests to the review mailing list 🚫.
It's suggested that multiple Designated Experts be appointed who can represent the perspectives of different applications using this spec, so the reviews are broadly informed 👯. If a decision could be seen as a conflict of interest for a particular Expert, that Expert should defer to the judgment of the other Experts 🫶.
7.1. JSON Web Signature and Encryption Algorithms Registry
This spec establishes the IANA "JSON Web Signature and Encryption Algorithms" registry for values of the JWS and JWE "alg" (algorithm) and "enc" (encryption algorithm) Header Parameters 🔐. The registry records the algorithm name, the algorithm description, the algorithm usage locations, the implementation requirements, the change controller, and a reference to the specification that defines it 🗂️. The same algorithm name can be registered multiple times, as long as the sets of usage locations are disjoint 🧩.
It's suggested that the length of the key be included in the algorithm name when multiple variations of an algorithm are registered that use keys of different lengths, and the key lengths for each need to be fixed (for instance, because they'll be created by key derivation functions). This lets readers of the JSON text make security decisions more easily 🔍.
The Designated Experts should do reasonable due diligence to make sure the algorithms being registered either are currently considered cryptographically credible or are being registered as Deprecated or Prohibited 🕵️♀️.
The implementation requirements of an algorithm may be changed over time as the cryptographic landscape evolves 🌦️. For example, an algorithm's status might change to Deprecated, or move from Optional to Recommended+ or Required. Changes to implementation requirements are only permitted on a Specification Required basis, after review by the Designated Experts, with the new specification defining the revised implementation requirements level 📝.
7.1.1. Registration Template
Algorithm Name: The name requested (e.g., HS256). This name is a case-sensitive ASCII string. Names may not match other registered names in a case-insensitive manner, unless the Designated Experts state that there's a compelling reason to allow an exception 🔤.
Algorithm Description: A brief description of the algorithm (e.g., "HMAC using SHA-256") 📖.
Algorithm Usage Location(s): The algorithm usage locations. This must be one or more of the values alg or enc if the algorithm is to be used with JWS or JWE. The value JWK is used if the algorithm identifier will be used as a JWK alg member value but won't be used with JWS or JWE; this could be the case, for instance, for non-authenticated encryption algorithms 🧾. Other values may be used with the approval of a Designated Expert 👀.
JOSE Implementation Requirements: The algorithm implementation requirements for JWS and JWE, which must be one of the words Required, Recommended, Optional, Deprecated, or Prohibited. Optionally, the word can be followed by a + or - 🎀.
- The use of
+indicates that the requirement strength is likely to be increased in a future version of the specification 📈. - The use of
-indicates that the requirement strength is likely to be decreased in a future version of the specification 📉.
Any identifiers registered for non-authenticated encryption algorithms, or for other algorithms that are otherwise unsuitable for direct use as JWS or JWE algorithms, must be registered as Prohibited 🚫.
Change Controller: For Standards Track RFCs, list the IESG. For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included 📮.
Specification Document(s): A reference to the document or documents that specify the parameter, preferably including URIs that can be used to retrieve copies of the documents 🔗. An indication of the relevant sections may also be included, but it's not required 📑.
Algorithm Analysis Documents(s): References to a publication or publications in well-known cryptographic conferences, by national standards bodies, or by other authoritative sources analyzing the cryptographic soundness of the algorithm to be registered 🧪. The Designated Experts may require convincing evidence of the cryptographic soundness of a new algorithm to be provided with the registration request, unless the algorithm is being registered as Deprecated or Prohibited. Having gone through working group and IETF review, the initial registrations made by this document are exempt from the need to provide this information 🎉.
7.1.2. Initial Registry Contents ✨
okay so this is the starter pack for the registry 🫶 every algorithm listed below gets its own entry, with the same fields as the template we just went over. the fields are: name, description, where it's used (alg or enc), the JOSE implementation requirement level, the change controller (always IESG here 🏛️), the spec section that defines it, and an analysis doc slot (all "n/a" bc nothing extra is needed). I've kept every entry exactly as it's written, typos and all, so nothing gets lost in translation 💅
The HMAC ones come first, starting with HS256 🔐
o Algorithm Name: "HS256"
o Algorithm Description: HMAC using SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 3.2 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "HS384"
o Algorithm Description: HMAC using SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.2 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "HS512"
o Algorithm Description: HMAC using SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.2 of RFC 7518
o Algorithm Analysis Documents(s): n/aNext up are the RSASSA-PKCS1-v1_5 signers 🧡
o Algorithm Name: "RS256"
o Algorithm Description: RSASSA-PKCS1-v1_5 using SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 3.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RS384"
o Algorithm Description: RSASSA-PKCS1-v1_5 using SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RS512"
o Algorithm Description: RSASSA-PKCS1-v1_5 using SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.3 of RFC 7518
o Algorithm Analysis Documents(s): n/aThen the ECDSA crew 🌸
o Algorithm Name: "ES256"
o Algorithm Description: ECDSA using P-256 and SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 3.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ES384"
o Algorithm Description: ECDSA using P-384 and SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ES512"
o Algorithm Description: ECDSA using P-521 and SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.4 of RFC 7518
o Algorithm Analysis Documents(s): n/aThe RSASSA-PSS ones are next 🦋
o Algorithm Name: "PS256"
o Algorithm Description: RSASSA-PSS using SHA-256 and MGF1 with
SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PS384"
o Algorithm Description: RSASSA-PSS using SHA-384 and MGF1 with
SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PS512"
o Algorithm Description: RSASSA-PSS using SHA-512 and MGF1 with
SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.5 of RFC 7518
o Algorithm Analysis Documents(s): n/aNow the "none" entry, plus the RSA encryption ones 🙈
o Algorithm Name: "none"
o Algorithm Description: No digital signature or MAC performed
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RSA1_5"
o Algorithm Description: RSAES-PKCS1-v1_5
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended-
o Change Controller: IESG
o Specification Document(s): Section 4.2 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RSA-OAEP"
o Algorithm Description: RSAES OAEP using default parameters
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 4.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RSA-OAEP-256"
o Algorithm Description: RSAES OAEP using SHA-256 and MGF1 with
SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.3 of RFC 7518
o Algorithm Analysis Documents(s): n/aThe AES Key Wrap entries 🎀
o Algorithm Name: "A128KW"
o Algorithm Description: AES Key Wrap using 128-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A192KW"
o Algorithm Description: AES Key Wrap using 192-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A256KW"
o Algorithm Description: AES Key Wrap using 256-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.4 of RFC 7518
o Algorithm Analysis Documents(s): n/aThe direct-key one and the ECDH-ES family 💜
o Algorithm Name: "dir"
o Algorithm Description: Direct use of a shared symmetric key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ECDH-ES"
o Algorithm Description: ECDH-ES using Concat KDF
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ECDH-ES+A128KW"
o Algorithm Description: ECDH-ES using Concat KDF and "A128KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ECDH-ES+A192KW"
o Algorithm Description: ECDH-ES using Concat KDF and "A192KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ECDH-ES+A256KW"
o Algorithm Description: ECDH-ES using Concat KDF and "A256KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/aThe AES GCM key wrapping and PBES2 entries 🌈
o Algorithm Name: "A128GCMKW"
o Algorithm Description: Key wrapping with AES GCM using 128-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.7 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A192GCMKW"
o Algorithm Description: Key wrapping with AES GCM using 192-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.7 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A256GCMKW"
o Algorithm Description: Key wrapping with AES GCM using 256-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.7 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PBES2-HS256+A128KW"
o Algorithm Description: PBES2 with HMAC SHA-256 and "A128KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PBES2-HS384+A192KW"
o Algorithm Description: PBES2 with HMAC SHA-384 and "A192KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PBES2-HS512+A256KW"
o Algorithm Description: PBES2 with HMAC SHA-512 and "A256KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of RFC 7518
o Algorithm Analysis Documents(s): n/aLast but not least, the content encryption ones, which are the enc side of things 🔥
o Algorithm Name: "A128CBC-HS256"
o Algorithm Description: AES_128_CBC_HMAC_SHA_256 authenticated
encryption algorithm
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 5.2.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A192CBC-HS384"
o Algorithm Description: AES_192_CBC_HMAC_SHA_384 authenticated
encryption algorithm
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 5.2.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A256CBC-HS512"
o Algorithm Description: AES_256_CBC_HMAC_SHA_512 authenticated
encryption algorithm
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 5.2.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A128GCM"
o Algorithm Description: AES GCM using 128-bit key
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 5.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A192GCM"
o Algorithm Description: AES GCM using 192-bit key
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 5.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A256GCM"
o Algorithm Description: AES GCM using 256-bit key
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 5.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a7.2. Header Parameter Names Registration
okay and now for the header parameter names 🎀 this section registers the Header Parameter names defined in Sections 4.6.1, 4.7.1, and 4.8.1 of this specification into the IANA "JSON Web Signature and Encryption Header Parameters" registry, which was set up by [JWS] 🧚 so those names get a permanent home in that registry, and the whole thing is officially on the record now ✨
7.2.1. Registry Contents 💖
okay so here's the actual registry, bestie 🎀 every entry tells you who uses the header, who controls changes, and where it's specified:
o Header Parameter Name: "epk"
o Header Parameter Description: Ephemeral Public Key
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.6.1.1 of RFC 7518
o Header Parameter Name: "apu"
o Header Parameter Description: Agreement PartyUInfo
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.6.1.2 of RFC 7518
o Header Parameter Name: "apv"
o Header Parameter Description: Agreement PartyVInfo
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.6.1.3 of RFC 7518
o Header Parameter Name: "iv"
o Header Parameter Description: Initialization Vector
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.7.1.1 of RFC 7518
o Header Parameter Name: "tag"
o Header Parameter Description: Authentication Tag
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.7.1.2 of RFC 7518
o Header Parameter Name: "p2s"
o Header Parameter Description: PBES2 Salt Input
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.8.1.1 of RFC 7518
o Header Parameter Name: "p2c"
o Header Parameter Description: PBES2 Count
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.8.1.2 of RFC 75187.3. JSON Web Encryption Compression Algorithms Registry ✨
this spec sets up the IANA "JSON Web Encryption Compression Algorithms" registry for the JWE "zip" member values 🧚 each entry records the compression algorithm value plus a reference to the spec that defines it.
7.3.1. Registration Template 💅
Compression Algorithm Value: pick the name you want, like "DEF". since the whole point is for the representations to be compact, it is RECOMMENDED that the name be short, not to exceed 8 characters without a compelling reason to do so. the name is case sensitive ✨ names may not match other registered names in a case-insensitive manner unless the Designated Experts state that there is a compelling reason to allow an exception.
Compression Algorithm Description: a brief description of the compression algorithm, like "DEFLATE" 🍓
Change Controller: for Standards Track RFCs, list "IESG". for everyone else, give the name of the responsible party. other details (like a postal address, email address, or home page URI) may also be included 💌
Specification Document(s): point to the document or documents that specify it, ideally with URIs where people can grab copies. indicating the relevant sections may also be included, but it is not required 📚
7.3.2. Initial Registry Contents 🌸
o Compression Algorithm Value: "DEF"
o Compression Algorithm Description: DEFLATE
o Change Controller: IESG
o Specification Document(s): JSON Web Encryption (JWE) [JWE]7.4. JSON Web Key Types Registry 👑
this spec establishes the IANA "JSON Web Key Types" registry for values of the JWK "kty" (key type) parameter. the registry records the "kty" value, implementation requirements, and a reference to the spec that defines it.
the implementation requirements of a key type can shift over time as the cryptographic landscape evolves. that could mean moving a key type to Deprecated, or moving it from Optional to Recommended+ or Required. changes to implementation requirements are only permitted on a Specification Required basis, after review by the Designated Experts, with the new specification defining the revised implementation requirements level. 🔥
7.4.1. Registration Template 🫶
"kty" Parameter Value: the name requested, like "EC". it is RECOMMENDED that the name be short, not to exceed 8 characters without a compelling reason to do so. the name is case sensitive, and names may not match other registered names in a case-insensitive manner unless the Designated Experts state that there is a compelling reason to allow an exception ✨
Key Type Description: a brief description of the key type, like "Elliptic Curve" 🦋
Change Controller: for Standards Track RFCs, list "IESG". for others, give the name of the responsible party. other details (like a postal address, email address, or home page URI) may also be included 💌
JOSE Implementation Requirements: the key type implementation requirements for JWS and JWE. it must be one the words Required, Recommended, Optional, Deprecated, or Prohibited. you can optionally follow the word with a "+" or "-". a "+" means the requirement strength is likely to be increased in a future version of the specification, and a "-" means it is likely to be decreased 💀
Specification Document(s): point to the document or documents that specify it, ideally with URIs where people can grab copies. indicating the relevant sections may also be included, but it is not required 📚
7.4.2. Initial Registry Contents 🧚
This section registers the values defined in Section 6.1.
o "kty" Parameter Value: "EC"
o Key Type Description: Elliptic Curve
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 6.2 of RFC 7518
o "kty" Parameter Value: "RSA"
o Key Type Description: RSA
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 6.3 of RFC 7518
o "kty" Parameter Value: "oct"
o Key Type Description: Octet Sequence
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 6.4 of RFC 75187.5. JSON Web Key Parameters Registration 🌈
this section registers the parameter names defined in Sections 6.2, 6.3, and 6.4 of this specification in the IANA "JSON Web Key Parameters" registry established by [JWK] 🎀
7.5.1. Registry Contents 💜
o Parameter Name: "crv"
o Parameter Description: Curve
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.1 of RFC 7518
o Parameter Name: "x"
o Parameter Description: X Coordinate
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.2 of RFC 7518
o Parameter Name: "y"
o Parameter Description: Y Coordinate
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.3 of RFC 7518
o Parameter Name: "d"
o Parameter Description: ECC Private Key
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.2.2.1 of RFC 7518
o Parameter Name: "n"
o Parameter Description: Modulus
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.3.1.1 of RFC 7518
o Parameter Name: "e"
o Parameter Description: Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.3.1.2 of RFC 7518
o Parameter Name: "d"
o Parameter Description: Private Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.1 of RFC 7518
o Parameter Name: "p"
o Parameter Description: First Prime Factor
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.2 of RFC 7518
o Parameter Name: "q"
o Parameter Description: Second Prime Factor
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.3 of RFC 7518
o Parameter Name: "dp"
o Parameter Description: First Factor CRT Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.4 of RFC 7518
o Parameter Name: "dq"
o Parameter Description: Second Factor CRT Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.5 of RFC 7518
o Parameter Name: "qi"
o Parameter Description: First CRT Coefficient
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.6 of RFC 7518
o Parameter Name: "oth"
o Parameter Description: Other Primes Info
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.7 of RFC 7518
o Parameter Name: "k"
o Parameter Description: Key Value
o Used with "kty" Value(s): "oct"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.4.1 of RFC 75187.6. JSON Web Key Elliptic Curve Registry 🦋
this section establishes the IANA "JSON Web Key Elliptic Curve" registry for JWK "crv" member values. the registry records the curve name, implementation requirements, and a reference to the spec that defines it. this specification registers the parameter names defined in Section 6.2.1.1 ✨
the implementation requirements of a curve can change over time as the cryptographic landscape evolves, like switching a curve to Deprecated, or moving a curve from Optional to Recommended+ or Required. changes of implementation requirements are only permitted on a Specification Required basis after review by the Designated Experts, with the new specification defining the revised implementation requirements level. 👑
7.6.1. Registration Template ✨
Curve Name: okay so the name requested (e.g., "P-256") 🎀 bestie, since the whole point of this spec is that the representations stay compact, it is RECOMMENDED that the name be short, not longer than 8 characters unless there's a compelling reason 💅. Names are case sensitive 🔠. They may not match other registered names in a case-insensitive way unless the Designated Experts say there's a compelling reason to allow an exception 🙈.
Curve Description: brief description of the curve (e.g., "P-256 Curve") 🦋.
JOSE Implementation Requirements: the curve implementation requirements for JWS and JWE. This must be one of the words Required, Recommended, Optional, Deprecated, or Prohibited. You can optionally follow the word with a "+" or "-" 🧚.
- A "+" means the requirement strength is likely to be increased in a future version of the specification 📈.
- A "-" means the requirement strength is likely to be decreased in a future version of the specification 📉.
Change Controller: for Standards Track RFCs, list "IESG". For everything else, give the name of the responsible party 🫶. Other details (like a postal address, email address, or home page URI) can be included too 🌸.
Specification Document(s): a reference to the document or documents that specify the parameter, ideally with URIs where you can grab copies 📚. Including the relevant sections is also allowed but not required ✨.
7.6.2. Initial Registry Contents 🌈
- Curve Name: "P-256"
- Curve Description: P-256 Curve
- JOSE Implementation Requirements: Recommended+
- Change Controller: IESG
- Specification Document(s): Section 6.2.1.1 of RFC 7518
- Curve Name: "P-384"
- Curve Description: P-384 Curve
- JOSE Implementation Requirements: Optional
- Change Controller: IESG
- Specification Document(s): Section 6.2.1.1 of RFC 7518
- Curve Name: "P-521"
- Curve Description: P-521 Curve
- JOSE Implementation Requirements: Optional
- Change Controller: IESG
- Specification Document(s): Section 6.2.1.1 of RFC 7518
8. Security Considerations 🔐
Bestie, this part is SERIOUS 😭. All of the security issues that are relevant to any cryptographic application must be addressed by JWS/JWE/JWK agents. That includes protecting the user's asymmetric private and symmetric secret keys and using countermeasures against various attacks 🛡️.
The security considerations in [AES], [DSS], [JWE], [JWK], [JWS], [NIST.800-38D], [NIST.800-56A], [NIST.800-107], [RFC2104], [RFC3394], [RFC3447], [RFC5116], [RFC6090], and [SHS] apply to this specification 📖.
8.1. Cryptographic Agility
Implementers should be aware that cryptographic algorithms get weaker over time 🕰️. As new cryptanalysis techniques come out and computers get faster, the work factor to break a given algorithm goes down. So implementers and deployments must be prepared for the set of algorithms they support and use to change over time 🔄. This means cryptographic algorithm implementations should be modular, so new algorithms can be slotted in easily 🧩.
8.2. Key Lifetimes
Lots of algorithms have security considerations tied to key lifetimes and/or how many times a key may be used ⏳. Those considerations still apply when you use those algorithms with JOSE data structures. For specific guidance on key lifetimes, see NIST SP 800-57 [NIST.800-57] 📘.
8.3. RSAES-PKCS1-v1_5 Security Considerations 🙃
While Section 8 of RFC 3447 [RFC3447] explicitly says people should not adopt RSASSA-PKCS1-v1_5 for new applications and asks them to move to RSASSA-PSS, this specification does include RSASSA-PKCS1-v1_5 🤷♀️. The reason is interoperability, because it's commonly implemented.
Keys used with RSAES-PKCS1-v1_5 must follow the constraints in Section 7.2 of RFC 3447. Also, keys with a low public key exponent value, as described in Section 3 of "Twenty Years of Attacks on the RSA Cryptosystem" [Boneh99], must not be used 🚫.
8.4. AES GCM Security Considerations 🔑
Keys used with AES GCM must follow the constraints in Section 8.3 of [NIST.800-38D], which states: "The total number of invocations of the authenticated encryption function shall not exceed 2^32, including all IV lengths and all instances of the authenticated encryption function with the given key". Following this rule, AES GCM MUST NOT be used with the same key value more than 2^32 times 🚨.
An IV value MUST NOT ever be used multiple times with the same AES GCM key 🙅♀️. One way to prevent this is to store a counter with the key and increment it every time you use it. The counter can also help you stay under the 2^32 limit above 🔢.
This security consideration does not apply to the composite AES-CBC HMAC SHA-2 or AES Key Wrap algorithms 💁♀️.
8.5. Unsecured JWS Security Considerations 👀
Unsecured JWSs (JWSs that use the "alg" value "none") provide no integrity protection 😬. So they must only be used in contexts where the payload is secured some other way than a digital signature or MAC value, or where it doesn't need to be secured at all.
Here's an example way to stop Unsecured JWSs from being accepted by default: a hypothetical JWS software library's "verify" method has a Boolean "acceptUnsecured" parameter that says whether "none" is an acceptable "alg" value. Another example is that the "verify" method might take a list of algorithms the application accepts as a parameter, and it would reject Unsecured JWS values if "none" isn't on that list 📝.
The following example shows why you should not accept Unsecured JWSs at a global level. Imagine an application accepts JWSs over two channels: (1) HTTP and (2) HTTPS with client authentication. It requires a JWS Signature on objects received over HTTP, but it accepts Unsecured JWSs over HTTPS. If the application globally said "none" is acceptable, an attacker could send it an Unsecured JWS over HTTP and the object would still validate successfully 😱. Instead, the application needs to accept "none" for each object received over HTTPS (for example, by setting "acceptUnsecured" to "true" for the first hypothetical JWS software library above), but not for each object received over HTTP 🧐.
8.6. Denial-of-Service Attacks 🌊
Receiving agents that validate signatures, and sending agents that encrypt messages, need to be careful about cryptographic processing usage when they validate signatures and encrypt messages with keys larger than those mandated in this specification ⚠️. An attacker could supply content using keys that cause excessive cryptographic processing, for example keys larger than those mandated in this specification. Implementations should set and enforce upper limits on the key sizes they accept. Section 5.6.1 (Comparable Algorithm Strengths) of NIST SP 800-57 [NIST.800-57] has statements on the largest approved key sizes that may be relevant 📏.
8.7. Reusing Key Material when Encrypting Keys 🔁
It is NOT RECOMMENDED to reuse the same entire set of key material (Key Encryption Key, Content Encryption Key, Initialization Vector, etc.) to encrypt multiple JWK or JWK Set objects, or to encrypt the same JWK or JWK Set object multiple times 🙅. One suggestion for preventing reuse is to always generate at least one new piece of key material for each encryption operation (e.g., a new Content Encryption Key, a new IV, and/or a new PBES2 Salt). This is based on the considerations in this document as well as RFC 4086 [RFC4086] 🎀.
8.8. Password Considerations 🔐💬
Passwords are vulnerable to a bunch of attacks 🥺. To help with some of these limitations, this document applies principles from RFC 2898 [RFC2898] to derive cryptographic keys from user-supplied passwords.
But the strength of the password still matters a LOT 💪. A high-entropy password is more resistant to dictionary attacks. [NIST.800-63-2] has guidelines for estimating password entropy, which can help applications and users make stronger passwords ✨.
An ideal password is one that is as large as (or larger than) the derived key length. However, passwords larger than a certain algorithm-specific size get hashed first, which reduces an attacker's effective search space to the length of the hash algorithm 🧮. It is RECOMMENDED that a password used for "PBES2-HS256+A128KW" be no shorter than 16 octets and no longer than 128 octets, and that a password used for "PBES2-HS512+A256KW" be no shorter than 32 octets and no longer than 128 octets long 🫧.
Still, you need to be careful about where and how password-based encryption is used 🧐. These algorithms can still be vulnerable to dictionary-based attacks if the iteration count is too small. This is especially concerning if the algorithms protect data that an attacker can try to get past indefinitely, such as protected data stored on a file system 💀.
8.9. Key Entropy and Random Values 🎲
See Section 10.1 of [JWS] for security considerations on key entropy and random values 🍓.
8.10. Differences between Digital Signatures and MACs ✍️
See Section 10.5 of [JWS] for security considerations on the differences between digital signatures and MACs 🧁.
8.11. Using Matching Algorithm Strengths 💜
See Section 11.3 of [JWE] for security considerations on using matching algorithm strengths 🌷.
8.12. Adaptive Chosen-Ciphertext Attacks 🕵️♀️
See Section 11.4 of [JWE] for security considerations on adaptive chosen-ciphertext attacks 🧠.
8.13. Timing Attacks ⏱️
See Section 10.9 of [JWS] and Section 11.5 of [JWE] for security considerations on timing attacks 🫣.
8.14. RSA Private Key Representations and Blinding 🕶️
See Section 9.3 of [JWK] for security considerations on RSA private key representations and blinding 🦋.
9. Internationalization Considerations 🌍
Passwords obtained from users usually need preparation and normalization, because different input devices, locales, and so on can produce different octet sequences 🌏. It is RECOMMENDED that applications perform the steps outlined in [PRECIS] to prepare a password supplied directly by a user before doing key derivation and encryption 💖.
10. References 📚
10.1. Normative References 📚
okay bestie, this is the receipts section 🧾✨ every doc this spec leans on, listed in full, no skipping 💅
[AES]National Institute of Standards and Technology (NIST), "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001,<http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf>.[Boneh99]"Twenty Years of Attacks on the RSA Cryptosystem", Notices of the American Mathematical Society (AMS), Vol. 46, No. 2, pp. 203-213, 1999,<http://crypto.stanford.edu/~dabo/pubs/papers/RSA-survey.pdf>.[DSS]National Institute of Standards and Technology (NIST), "Digital Signature Standard (DSS)", FIPS PUB 186-4, July 2013,<http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf>.[JWE]Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015,<http://www.rfc-editor.org/info/rfc7516>.[JWK]Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015,<http://www.rfc-editor.org/info/rfc7517>.[JWS]Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015,<http://www.rfc-editor.org/info/rfc7515>.[NIST.800-38A]National Institute of Standards and Technology (NIST), "Recommendation for Block Cipher Modes of Operation", NIST Special Publication 800-38A, December 2001,<http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf>.[NIST.800-38D]National Institute of Standards and Technology (NIST), "Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC", NIST Special Publication 800-38D, December 2001,<http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf>.[NIST.800-56A]National Institute of Standards and Technology (NIST), "Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography", NIST Special Publication 800-56A, Revision 2, May 2013,<http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-56Ar2.pdf>.[NIST.800-57]National Institute of Standards and Technology (NIST), "Recommendation for Key Management - Part 1: General (Revision 3)", NIST Special Publication 800-57, Part 1, Revision 3, July 2012,<http://csrc.nist.gov/publications/nistpubs/800-57/sp800-57_part1_rev3_general.pdf>.[RFC20]Cerf, V., "ASCII format for Network Interchange", STD 80, RFC 20, DOI 10.17487/RFC0020, October 1969,<http://www.rfc-editor.org/info/rfc20>.[RFC2104]Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997,<http://www.rfc-editor.org/info/rfc2104>.[RFC2119]Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997,<http://www.rfc-editor.org/info/rfc2119>.[RFC2898]Kaliski, B., "PKCS #5: Password-Based Cryptography Specification Version 2.0", RFC 2898, DOI 10.17487/RFC2898, September 2000,<http://www.rfc-editor.org/info/rfc2898>.[RFC3394]Schaad, J. and R. Housley, "Advanced Encryption Standard (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394, September 2002,<http://www.rfc-editor.org/info/rfc3394>.[RFC3447]Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February 2003,<http://www.rfc-editor.org/info/rfc3447>.[RFC3629]Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003,<http://www.rfc-editor.org/info/rfc3629>.[RFC4868]Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 with IPsec", RFC 4868, DOI 10.17487/RFC4868, May 2007,<http://www.rfc-editor.org/info/rfc4868>.[RFC4949]Shirey, R., "Internet Security Glossary, Version 2", FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,<http://www.rfc-editor.org/info/rfc4949>.[RFC5652]Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009,<http://www.rfc-editor.org/info/rfc5652>.[RFC6090]McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic Curve Cryptography Algorithms", RFC 6090, DOI 10.17487/RFC6090, February 2011,<http://www.rfc-editor.org/info/rfc6090>.[RFC7159]Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014,<http://www.rfc-editor.org/info/rfc7159>.[SEC1]Standards for Efficient Cryptography Group, "SEC 1: Elliptic Curve Cryptography", Version 2.0, May 2009,<http://www.secg.org/sec1-v2.pdf>.[SHS]National Institute of Standards and Technology (NIST), "Secure Hash Standard (SHS)", FIPS PUB 180-4, March 2012,<http://csrc.nist.gov/publications/fips/fips180-4/fips-180-4.pdf>.[UNICODE]The Unicode Consortium, "The Unicode Standard",<http://www.unicode.org/versions/latest/>.
10.2. Informative References 🌸
these ones are the extra reading 🤓 good context, not required to build the thing, but so worth a look 🫶
[AEAD-CBC-SHA]McGrew, D., Foley, J., and K. Paterson, "Authenticated Encryption with AES-CBC and HMAC-SHA", Work in Progress, draft-mcgrew-aead-aes-cbc-hmac-sha2-05, July 2014.[CanvasApp]Facebook, "Canvas Applications", 2010,<http://developers.facebook.com/docs/authentication/canvas>.[JCA]Oracle, "Java Cryptography Architecture (JCA) Reference Guide", 2014,<http://docs.oracle.com/javase/8/docs/technotes/guides/security/crypto/CryptoSpec.html>.[JSE]Bradley, J. and N. Sakimura (editor), "JSON Simple Encryption", September 2010,<http://jsonenc.info/enc/1.0/>.[JSMS]Rescorla, E. and J. Hildebrand, "JavaScript Message Security Format", Work in Progress, draft-rescorla-jsms-00, March 2011.[JSS]Bradley, J. and N. Sakimura, Ed., "JSON Simple Sign 1.0", Draft 01, September 2010,<http://jsonenc.info/jss/1.0/>.[JWE-JWK]Miller, M., "Using JavaScript Object Notation (JSON) Web Encryption (JWE) for Protecting JSON Web Key (JWK) Objects", Work in Progress, draft-miller-jose-jwe-protected-jwk-02, June 2013.[MagicSignatures]Panzer, J., Ed., Laurie, B., and D. Balfanz, "Magic Signatures", January 2011,<http://salmon-protocol.googlecode.com/svn/trunk/draft-panzer-magicsig-01.html>.[NIST.800-107]National Institute of Standards and Technology (NIST), "Recommendation for Applications Using Approved Hash Algorithms", NIST Special Publication 800-107, Revision 1, August 2012,<http://csrc.nist.gov/publications/nistpubs/800-107-rev1/sp800-107-rev1.pdf>.[NIST.800-63-2]National Institute of Standards and Technology (NIST), "Electronic Authentication Guideline", NIST Special Publication 800-63-2, August 2013,<http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-63-2.pdf>.[PRECIS]Saint-Andre, P. and A. Melnikov, "Preparation, Enforcement, and Comparison of Internationalized Strings Representing Usernames and Passwords", Work in Progress, draft-ietf-precis-saslprepbis-16, April 2015.[RFC2631]Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC 2631, DOI 10.17487/RFC2631, June 1999,<http://www.rfc-editor.org/info/rfc2631>.[RFC3275]Eastlake 3rd, D., Reagle, J., and D. Solo, "(Extensible Markup Language) XML-Signature Syntax and Processing", RFC 3275, DOI 10.17487/RFC3275, March 2002,<http://www.rfc-editor.org/info/rfc3275>.[RFC4086]Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005,<http://www.rfc-editor.org/info/rfc4086>.[RFC5116]McGrew, D., "An Interface and Algorithms for Authenticated Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,<http://www.rfc-editor.org/info/rfc5116>.[RFC5226]Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008,<http://www.rfc-editor.org/info/rfc5226>.[W3C.NOTE-xmldsig-core2-20130411]Eastlake, D., Reagle, J., Solo, D., Hirsch, F., Roessler, T., Yiu, K., Datta, P., and S. Cantor, "XML Signature Syntax and Processing Version 2.0", World Wide Web Consortium Note NOTE-xmldsig-core2-20130411, April 2013,<http://www.w3.org/TR/2013/NOTE-xmldsig-core2-20130411/>.[W3C.REC-xmlenc-core-20021210]Eastlake, D. and J. Reagle, "XML Encryption Syntax and Processing", World Wide Web Consortium Recommendation REC-xmlenc-core-20021210, December 2002,<http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.[W3C.REC-xmlenc-core1-20130411]Eastlake, D., Reagle, J., Hirsch, F., and T. Roessler, "XML Encryption Syntax and Processing Version 1.1", World Wide Web Consortium Recommendation REC-xmlenc-core1-20130411, April 2013,<http://www.w3.org/TR/2013/REC-xmlenc-core1-20130411/>.
Appendix A. Algorithm Identifier Cross-Reference ✨
this appendix is the translation guide 🦋 it lines up the algorithm identifier values defined in this spec with the matching identifiers used by other standards and software packages, so you can tell who calls what 💖 for the details on the names those docs use, check out XML DSIG [RFC3275], XML DSIG 2.0 [W3C.NOTE-xmldsig-core2-20130411], XML Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1 [W3C.REC-xmlenc-core1-20130411], and Java Cryptography Architecture [JCA].
Appendix A. Algorithm Identifier Cross-Reference ✨
A.1. Digital Signature/MAC Algorithm Identifier Cross-Reference 🔐
okay so this table is basically a friendship map 🦋 It lines up every JWS digital signature and MAC alg value from this spec with the matching ID that other standards and software packages use for the same algorithm. So if you're working with XML DSIG, JCA, or OIDs, you can find your match here, no cap.
+-------------------------------------------------------------------+
| JWS | XML DSIG |
| | JCA | OID |
+-------------------------------------------------------------------+
| HS256 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha256 |
| | HmacSHA256 | 1.2.840.113549.2.9 |
+-------------------------------------------------------------------+
| HS384 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha384 |
| | HmacSHA384 | 1.2.840.113549.2.10 |
+-------------------------------------------------------------------+
| HS512 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha512 |
| | HmacSHA512 | 1.2.840.113549.2.11 |
+-------------------------------------------------------------------+
| RS256 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha256 |
| | SHA256withRSA | 1.2.840.113549.1.1.11 |
+-------------------------------------------------------------------+
| RS384 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha384 |
| | SHA384withRSA | 1.2.840.113549.1.1.12 |
+-------------------------------------------------------------------+
| RS512 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha512 |
| | SHA512withRSA | 1.2.840.113549.1.1.13 |
+-------------------------------------------------------------------+
| ES256 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256 |
| | SHA256withECDSA | 1.2.840.10045.4.3.2 |
+-------------------------------------------------------------------+
| ES384 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384 |
| | SHA384withECDSA | 1.2.840.10045.4.3.3 |
+-------------------------------------------------------------------+
| ES512 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512 |
| | SHA512withECDSA | 1.2.840.10045.4.3.4 |
+-------------------------------------------------------------------+
| PS256 | http://www.w3.org/2007/05/xmldsig-more#sha256-rsa-MGF1 |
| | SHA256withRSAandMGF1 | 1.2.840.113549.1.1.10 |
+-------------------------------------------------------------------+
| PS384 | http://www.w3.org/2007/05/xmldsig-more#sha384-rsa-MGF1 |
| | SHA384withRSAandMGF1 | 1.2.840.113549.1.1.10 |
+-------------------------------------------------------------------+
| PS512 | http://www.w3.org/2007/05/xmldsig-more#sha512-rsa-MGF1 |
| | SHA512withRSAandMGF1 | 1.2.840.113549.1.1.10 |
+-------------------------------------------------------------------+A.2. Key Management Algorithm Identifier Cross-Reference 🗝️
this one's the key management version 💅 This table matches the JWE alg values from this spec with their equivalents in other standards and software packages. Same energy as the last table, just for key stuff, so you can keep your IDs consistent across the board 🌸
+-------------------------------------------------------------------+
| JWE | XML ENC |
| | JCA | OID |
+-------------------------------------------------------------------+
| RSA1_5 | http://www.w3.org/2001/04/xmlenc#rsa-1_5 |
| | RSA/ECB/PKCS1Padding | 1.2.840.113549.1.1.1 |
+-------------------------------------------------------------------+
| RSA-OAEP | http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p |
| | RSA/ECB/OAEPWithSHA-1AndMGF1Padding | 1.2.840.113549.1.1.7 |
+-------------------------------------------------------------------+
| RSA-OAEP-256 | http://www.w3.org/2009/xmlenc11#rsa-oaep |
| | & http://www.w3.org/2009/xmlenc11#mgf1sha256 |
| | RSA/ECB/OAEPWithSHA-256AndMGF1Padding | |
| | & MGF1ParameterSpec.SHA256 | 1.2.840.113549.1.1.7 |
+-------------------------------------------------------------------+
| ECDH-ES | http://www.w3.org/2009/xmlenc11#ECDH-ES |
| | ECDH | 1.3.132.1.12 |
+-------------------------------------------------------------------+
| A128KW | http://www.w3.org/2001/04/xmlenc#kw-aes128 |
| | AESWrap | 2.16.840.1.101.3.4.1.5 |
+-------------------------------------------------------------------+
| A192KW | http://www.w3.org/2001/04/xmlenc#kw-aes192 |
| | AESWrap | 2.16.840.1.101.3.4.1.25 |
+-------------------------------------------------------------------+
| A256KW | http://www.w3.org/2001/04/xmlenc#kw-aes256 |
| | AESWrap | 2.16.840.1.101.3.4.1.45 |
+-------------------------------------------------------------------+A.3. Content Encryption Algorithm Identifier Cross-Reference 🎀
last table in this appendix, bestie 🥹 This one lines up the JWE enc values (the content encryption algorithms) with their equivalents elsewhere. For the composite algorithms A128CBC-HS256, A192CBC-HS384, and A256CBC-HS512, it lists the matching AES-CBC identifiers, since those are the parts they're built on 💜
+-------------------------------------------------------------------+
| JWE | XML ENC |
| | JCA | OID |
+-------------------------------------------------------------------+
| A128CBC-HS256 | http://www.w3.org/2001/04/xmlenc#aes128-cbc |
| | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.2 |
+-------------------------------------------------------------------+
| A192CBC-HS384 | http://www.w3.org/2001/04/xmlenc#aes192-cbc |
| | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.22 |
+-------------------------------------------------------------------+
| A256CBC-HS512 | http://www.w3.org/2001/04/xmlenc#aes256-cbc |
| | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.42 |
+-------------------------------------------------------------------+
| A128GCM | http://www.w3.org/2009/xmlenc11#aes128-gcm |
| | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.6 |
+-------------------------------------------------------------------+
| A192GCM | http://www.w3.org/2009/xmlenc11#aes192-gcm |
| | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.26 |
+-------------------------------------------------------------------+
| A256GCM | http://www.w3.org/2009/xmlenc11#aes256-gcm |
| | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.46 |
+-------------------------------------------------------------------+Appendix B. Test Cases for AES_CBC_HMAC_SHA2 Algorithms 🧪
these test cases are the ultimate reality check ✨ You can use them to validate your AES_CBC_HMAC_SHA2 implementation, which is defined in Section 5.2. They're also meant to line up with test cases that might show up in a future version of [AEAD-CBC-SHA], proving the cryptographic computations come out the same 🔥 Every variable name matches what Section 5.2 uses, and all the values are hexadecimal, so no surprises there 💖
B.1. Test Cases for AES_128_CBC_HMAC_SHA_256 💅
first up is the 128-bit one 🌈
AES_128_CBC_HMAC_SHA_256
K = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
ENC_KEY = 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
P = 41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65
IV = 1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04
A = 54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
4b 65 72 63 6b 68 6f 66 66 73
AL = 00 00 00 00 00 00 01 50
E = c8 0e df a3 2d df 39 d5 ef 00 c0 b4 68 83 42 79
a2 e4 6a 1b 80 49 f7 92 f7 6b fe 54 b9 03 a9 c9
a9 4a c9 b4 7a d2 65 5c 5f 10 f9 ae f7 14 27 e2
fc 6f 9b 3f 39 9a 22 14 89 f1 63 62 c7 03 23 36
09 d4 5a c6 98 64 e3 32 1c f8 29 35 ac 40 96 c8
6e 13 33 14 c5 40 19 e8 ca 79 80 df a4 b9 cf 1b
38 4c 48 6f 3a 54 c5 10 78 15 8e e5 d7 9d e5 9f
bd 34 d8 48 b3 d6 95 50 a6 76 46 34 44 27 ad e5
4b 88 51 ff b5 98 f7 f8 00 74 b9 47 3c 82 e2 db
M = 65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4
e6 e5 45 82 47 65 15 f0 ad 9f 75 a2 b7 1c 73 ef
T = 65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4B.2. Test Cases for AES_192_CBC_HMAC_SHA_384 🌸
and now the 192-bit version, with the bigger keys and tags 💜
K = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17
ENC_KEY = 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27
28 29 2a 2b 2c 2d 2e 2f
P = 41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65
IV = 1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04
A = 54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
4b 65 72 63 6b 68 6f 66 66 73
AL = 00 00 00 00 00 00 01 50
E = ea 65 da 6b 59 e6 1e db 41 9b e6 2d 19 71 2a e5
d3 03 ee b5 00 52 d0 df d6 69 7f 77 22 4c 8e db
00 0d 27 9b dc 14 c1 07 26 54 bd 30 94 42 30 c6
57 be d4 ca 0c 9f 4a 84 66 f2 2b 22 6d 17 46 21
4b f8 cf c2 40 0a dd 9f 51 26 e4 79 66 3f c9 0b
3b ed 78 7a 2f 0f fc bf 39 04 be 2a 64 1d 5c 21
05 bf e5 91 ba e2 3b 1d 74 49 e5 32 ee f6 0a 9a
c8 bb 6c 6b 01 d3 5d 49 78 7b cd 57 ef 48 49 27
f2 80 ad c9 1a c0 c4 e7 9c 7b 11 ef c6 00 54 e3
M = 84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
75 16 80 39 cc c7 33 d7 45 94 f8 86 b3 fa af d4
86 f2 5c 71 31 e3 28 1e 36 c7 a2 d1 30 af de 57
T = 84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
75 16 80 39 cc c7 33 d7B.3. Test Cases for AES_256_CBC_HMAC_SHA_512Okay bestie, this part is the last one, so let's finish strong 💅🎀. We're picking up with the third AES_CBC_HMAC_SHA2 test case, the big boy with the 512-bit SHA. Everything below is the exact hex from the spec, so don't you dare touch a single byte 😭.
K = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
ENC_KEY = 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
P = 41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65
IV = 1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04
A = 54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
4b 65 72 63 6b 68 6f 66 66 73
AL = 00 00 00 00 00 00 01 50
E = 4a ff aa ad b7 8c 31 c5 da 4b 1b 59 0d 10 ff bd
3d d8 d5 d3 02 42 35 26 91 2d a0 37 ec bc c7 bd
82 2c 30 1d d6 7c 37 3b cc b5 84 ad 3e 92 79 c2
e6 d1 2a 13 74 b7 7f 07 75 53 df 82 94 10 44 6b
36 eb d9 70 66 29 6a e6 42 7e a7 5c 2e 08 46 a1
1a 09 cc f5 37 0d c8 0b fe cb ad 28 c7 3f 09 b3
a3 b7 5e 66 2a 25 94 41 0a e4 96 b2 e2 e6 60 9e
31 e6 e0 2c c8 37 f0 53 d2 1f 37 ff 4f 51 95 0b
be 26 38 d0 9d d7 a4 93 09 30 80 6d 07 03 b1 f6
M = 4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5
fd 30 a5 65 c6 16 ff b2 f3 64 ba ec e6 8f c4 07
53 bc fc 02 5d de 36 93 75 4a a1 f5 c3 37 3b 9c
T = 4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5Appendix C. Example ECDH-ES Key Agreement Computation ✨
C. Example ECDH-ES Key Agreement Computation 🦋
Okay so this example is giving key agreement realness 🔥. It uses ECDH-ES plus the Concat KDF to derive the CEK, the way Section 4.6 describes. The ECDH-ES Direct Key Agreement mode (that's the alg value "ECDH-ES") makes an agreed-upon key for AES GCM with a 128-bit key (the enc value "A128GCM"). Iconic 💜.
Our producer is Alice, and she's encrypting content for her consumer, Bob 🫶. Alice makes an ephemeral key for the key agreement computation. Her ephemeral key, in JWK format and including the private part, is:
{"kty":"EC",
"crv":"P-256",
"x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
"y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps",
"d":"0_NxaRPUMQoAJt50Gz8YiTr8gRTwyEaCumd-MToTmIo"
}Bob's key, also in JWK format and including the private part, looks like this 🌸:
{"kty":"EC",
"crv":"P-256",
"x":"weNJy2HscCSM6AEDTDg04biOvhFhyyWvOHQfeF_PxMQ",
"y":"e8lnCO-AlStT-NJVX-crhB7QRYhiix03illJOVAOyck",
"d":"VEmDZpDXXK8p8N0Cndsxs924q6nS1RXFASRl6BfUqdw"
}Now the Header Parameter values. The "apu" (agreement PartyUInfo) value is the base64url encoding of the UTF-8 string "Alice", and the "apv" (agreement PartyVInfo) value is the base64url encoding of the UTF-8 string "Bob". The "epk" (ephemeral public key) Header Parameter is how Alice tells Bob her ephemeral public key value 🧚.
{"alg":"ECDH-ES",
"enc":"A128GCM",
"apu":"QWxpY2U",
"apv":"Qm9i",
"epk":
{"kty":"EC",
"crv":"P-256",
"x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
"y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps"
}
}The resulting Concat KDF [NIST.800-56A] parameter values are below. Let's go 👑.
Z : This is set to the ECDH-ES key agreement output. (This value is often not directly exposed by libraries, due to NIST security requirements, and only serves as an input to a KDF.) In this example, Z is the following octet sequence (using JSON array notation):
[158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132,
38, 156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121,
140, 254, 144, 196]keydatalen : This value is 128, the number of bits in the desired output key (because "A128GCM" uses a 128-bit key). Easy peasy 🍓.
AlgorithmID : This is set to the octets for the 32-bit big-endian value 7, which is [0, 0, 0, 7], the number of octets in the AlgorithmID content "A128GCM". That gets followed by the octets for the ASCII string "A128GCM", which is [65, 49, 50, 56, 71, 67, 77].
PartyUInfo : This is set to the octets for the 32-bit big-endian value 5, which is [0, 0, 0, 5], the number of octets in the PartyUInfo content "Alice". That gets followed by the octets for the UTF-8 string "Alice", which is [65, 108, 105, 99, 101].
PartyVInfo : This is set to the octets for the 32-bit big-endian value 3, which is [0, 0, 0, 3], the number of octets in the PartyUInfo content "Bob". That gets followed by the octets for the UTF-8 string "Bob", which is [66, 111, 98]. (Yes, the spec says PartyUInfo there, and yes, we're counting Bob's length. Iykyk 🙈.)
SuppPubInfo : This is set to the octets for the 32-bit big-endian value 128, which is [0, 0, 0, 128], the keydatalen value.
SuppPrivInfo : This is set to the empty octet sequence.
Concatenating the parameters AlgorithmID through SuppPubInfo gives an OtherInfo value of:
[0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105,
99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]Concatenating the round number 1 ([0, 0, 0, 1]), Z, and the OtherInfo value gives the Concat KDF round 1 hash input of:
[0, 0, 0, 1,
158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132, 38,
156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121, 140,
254, 144, 196,
0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99,
101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]The resulting derived key, which is the first 128 bits of the round 1 hash output, is:
[86, 170, 141, 234, 248, 35, 109, 32, 92, 34, 40, 205, 113, 167, 16,
26]The base64url-encoded representation of this derived key is:
VqqN6vgjbSBcIijNcacQGgAcknowledgements 💖
Solutions for signing and encrypting JSON content were explored earlier by "Magic Signatures" [MagicSignatures], "JSON Simple Sign 1.0" [JSS], "Canvas Applications" [CanvasApp], "JSON Simple Encryption" [JSE], and "JavaScript Message Security Format" [JSMS]. All of them influenced this document, so they get a big group hug 🫶.
The "Authenticated Encryption with AES-CBC and HMAC-SHA" [AEAD-CBC-SHA] specification is what the AES_CBC_HMAC_SHA2 algorithms are based on. David A. McGrew and Kenny Paterson wrote it 🌈. The test cases for AES_CBC_HMAC_SHA2 are based on the ones for [AEAD-CBC-SHA] by John Foley.
Matt Miller wrote "Using JavaScript Object Notation (JSON) Web Encryption (JWE) for Protecting JSON Web Key (JWK) Objects" [JWE-JWK], and the password-based encryption content of this document is based on it ⭐.
This specification is the work of the JOSE working group, which has dozens of active and dedicated participants 💅. These individuals contributed ideas, feedback, and wording that shaped this specification: Dirk Balfanz, Richard Barnes, Carsten Bormann, John Bradley, Brian Campbell, Alissa Cooper, Breno de Medeiros, Vladimir Dzhuvinov, Roni Even, Stephen Farrell, Yaron Y. Goland, Dick Hardt, Joe Hildebrand, Jeff Hodges, Edmund Jay, Charlie Kaufman, Barry Leiba, James Manger, Matt Miller, Kathleen Moriarty, Tony Nadalin, Axel Nennker, John Panzer, Emmanuel Raviart, Eric Rescorla, Pete Resnick, Nat Sakimura, Jim Schaad, Hannes Tschofenig, and Sean Turner. Literal legends 👑.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group. Sean Turner, Stephen Farrell, and Kathleen Moriarty served as Security Area Directors while this specification was being created 🔥.
Author's Address 🎀
Michael B. Jones Microsoft
EMail: mbj@microsoft.com URI: http://self-issued.info/
📦 where this page comes from
- ietf: rfc7518 2015-05
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms