RFC 5753

Use of Elliptic Curve Cryptography (ECC) Algorithms in Cryptographic Message Syntax (CMS)

📅 published January 2010, from ietf

RFC 5753: Use of Elliptic Curve Cryptography (ECC) Algorithms in Cryptographic Message Syntax (CMS) 🦋

okay bestie, this one is from January 2010 and it's an Informational RFC (so not a Standards Track thing 💅), written by S. Turner of IECA and D. Brown of Certicom. It's published under the ISSN 2070-1721, and it obsoletes RFC 3278 🫶. The main vibe: it's a profile for using ECC public key algorithms inside CMS, so it's basically the instruction manual for how ECC gets plugged into CMS 🔥.

Abstract

This document describes how to use Elliptic Curve Cryptography (ECC) public key algorithms in the Cryptographic Message Syntax (CMS) ✨. The ECC algorithms support creating digital signatures and exchanging keys so you can encrypt or authenticate content 🔐. The algorithm processing is based on NIST FIPS 186-3 for digital signatures, NIST SP800-56A and SEC1 for key agreement, RFC 3370 and RFC 3565 for key wrap and content encryption, NIST FIPS 180-3 for message digests, SEC1 for key derivation, and RFC 2104 and RFC 4231 for message authentication code standards 📚. And yes, this document obsoletes RFC 3278 💖.

Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes 🌸.

This document is a product of the Internet Engineering Task Force (IETF) 🎀. It represents the consensus of the IETF community, it has received public review, and it has been approved for publication by the Internet Engineering Steering Group (IESG) 👑. Not all documents approved by the IESG are a candidate for any level of Internet Standard, so check out Section 2 of RFC 5741 if you want the full tea ☕.

You can find info about the current status of this document, any errata, and how to give feedback at http://www.rfc-editor.org/info/rfc5753 🦋.

Copyright (c) 2010 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) in effect on the date of publication of this document. Please review these documents carefully, because they describe your rights and restrictions with respect to this document 💜. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they are provided without warranty as described in the Simplified BSD License 📜.

This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English 🙈.

Table of Contents

   1. Introduction ....................................................3
      1.1. Requirements Terminology ...................................3
   2. SignedData Using ECC ............................................3
      2.1. SignedData Using ECDSA .....................................4
   3. EnvelopedData Using ECC Algorithms ..............................5
      3.1. EnvelopedData Using (ephemeral-static) ECDH ................5
      3.2. EnvelopedData Using 1-Pass ECMQV ...........................8
   4. AuthenticatedData and AuthEnvelopedData Using ECC ..............11
      4.1. AuthenticatedData Using 1-Pass ECMQV ......................11
      4.2. AuthEnvelopedData Using 1-Pass ECMQV ......................12
   5. Certificates Using ECC .........................................13
   6. SMIMECapabilities Attribute and ECC ............................13
   7. ASN.1 Syntax ...................................................21
      7.1. Algorithm Identifiers .....................................21
      7.2. Other Syntax ..............................................24
   8. Recommended Algorithms and Elliptic Curves .....................26
   9. Security Considerations ........................................28
   10. IANA Considerations ...........................................33
   11. References ....................................................33
      11.1. Normative References .....................................33
      11.2. Informative References ...................................35
   Appendix A.  ASN.1 Modules.........................................37
      A.1.  1988 ASN.1 Module.........................................37
      A.2.  2004 ASN.1 Module.........................................45
   Appendix B. Changes since RFC 3278.................................59
   Acknowledgements...................................................61

1. Introduction ✨

The Cryptographic Message Syntax (CMS) is cryptographic algorithm independent 🧚. This specification defines a profile for using Elliptic Curve Cryptography (ECC) public key algorithms in CMS. The ECC algorithms get built into the following CMS content types 💅:

  • 'SignedData' to support ECC-based digital signature methods (ECDSA) to sign content 🖊️;
  • 'EnvelopedData' to support ECC-based public key agreement methods (ECDH and ECMQV) to generate pairwise key-encryption keys, which are used to encrypt content-encryption keys for content encryption 🔑;
  • 'AuthenticatedData' to support ECC-based public key agreement methods (ECMQV) to generate pairwise key-encryption keys, which are used to encrypt message-authentication keys for content authentication and integrity 🛡️; and
  • 'AuthEnvelopedData' to support ECC-based public key agreement methods (ECMQV) to generate pairwise key-encryption keys, which are used to encrypt message-authentication and content-encryption keys for content authentication, integrity, and encryption 🌸.

Certification of EC public keys is also described, so public key distribution works with the techniques above 🎀.

This document will obsolete [CMS-ECC]. The technical changes made since RFC 3278 are detailed in Appendix B 📝.

1.1. Requirements Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [MUST] 🤓.

2. SignedData Using ECC

This section describes how to use ECC algorithms with the CMS SignedData format to sign data ✍️.

2.1. SignedData Using ECDSA

This section describes how to use the Elliptic Curve Digital Signature Algorithm (ECDSA) with SignedData 💖. ECDSA is specified in [FIPS186-3]. The method is the elliptic curve analog of the Digital Signature Algorithm (DSA) [FIPS186-3]. ECDSA is used with the Secure Hash Algorithm (SHA) [FIPS180-3] 🦄.

In an implementation that uses ECDSA with CMS SignedData, the following techniques and formats MUST be used. No skipping, bestie 🫶.

2.1.1. Fields of the SignedData

When using ECDSA with SignedData, the fields of SignerInfo are as in [CMS], but with the following restrictions 📋:

  • digestAlgorithm MUST contain the algorithm identifier of the hash algorithm (see Section 7.1.1), which MUST be one of the following: id-sha1, id-sha224, id-sha256, id-sha384, or id-sha512 🔍.
  • signatureAlgorithm contains the signature algorithm identifier (see Section 7.1.3): ecdsa-with-SHA1, ecdsa-with-SHA224, ecdsa-with-SHA256, ecdsa-with-SHA384, or ecdsa-with-SHA512. The hash algorithm identified in the name of the signature algorithm MUST be the same as the digestAlgorithm (e.g., if digestAlgorithm is id-sha256, then signatureAlgorithm is ecdsa-with-SHA256) 🧠.
  • signature MUST contain the DER encoding (as an octet string) of a value of the ASN.1 type ECDSA-Sig-Value (see Section 7.2) 🍓.

When using ECDSA, the SignedData certificates field MAY include the certificate(s) for the EC public key(s) used in the generation of the ECDSA signatures in SignedData 🎀. ECC certificates are discussed in Section 5 💅.

2.1.2. Actions of the Sending Agent

When using ECDSA with SignedData, the sending agent uses the message digest calculation process and signature generation process for SignedData that are specified in [CMS]. To sign data, the sending agent uses the signature method specified in [FIPS186-3] ✨.

The sending agent encodes the resulting signature using the ECDSA-Sig-Value syntax (see Section 7.2) and places it in the SignerInfo signature field 🌈.

2.1.3. Actions of the Receiving Agent

When using ECDSA with SignedData, the receiving agent uses the message digest calculation process and signature verification process for SignedData that are specified in [CMS]. To verify SignedData, the receiving agent uses the signature verification method specified in [FIPS186-3] 🔎.

In order to verify the signature, the receiving agent retrieves the integers r and s from the SignerInfo signature field of the received message 🧮.

3. EnvelopedData Using ECC Algorithms

This section describes how to use ECC algorithms with the CMS EnvelopedData format 💌.

This document does not specify the static-static ECDH, method C(0,2, ECC CDH) from [SP800-56A]. Static-static ECDH is analogous to static-static DH, which is specified in [CMS-ALG]. Ephemeral-static ECDH and 1-Pass ECMQV were specified because they provide better security, due to the originator's ephemeral contribution to the key agreement scheme 🥹🔥.

3.1. EnvelopedData Using (ephemeral-static) ECDH

This section describes how to use the ephemeral-static Elliptic Curve Diffie-Hellman (ECDH) key agreement algorithm with EnvelopedData 🍭. This algorithm has two variations:

  • 'Standard' ECDH, described as the 'Elliptic Curve Diffie-Hellman Scheme' with the 'Elliptic Curve Diffie-Hellman Primitive' in [SEC1], and
  • 'Co-factor' ECDH, described as the 'One-Pass Diffie-Hellman scheme' (method C(1, 1, ECC CDH)) in [SP800-56A].

Both variations of ephemeral-static ECDH are elliptic curve analogs of the ephemeral-static Diffie-Hellman key agreement algorithm, specified jointly in the documents [CMS-ALG] and [CMS-DH] 💜.

If an implementation uses ECDH with CMS EnvelopedData, then the following techniques and formats MUST be used 🫶.

The fields of EnvelopedData are as in [CMS]. Since ECDH is a key agreement algorithm, the RecipientInfo kari choice is used 🦋.

3.1.1. Fields of KeyAgreeRecipientInfo 🎀

okay so when you're doing ephemeral-static ECDH with EnvelopedData, here's what the fields of KeyAgreeRecipientInfo look like 💅

  • version MUST be 3.
  • originator MUST be the alternative originatorKey. The originatorKey algorithm field MUST contain the id-ecPublicKey object identifier (see Section 7.1.2). The parameters associated with id-ecPublicKey MUST be absent, ECParameters, or NULL. The parameters associated with id-ecPublicKey SHOULD be absent or ECParameters, and NULL is allowed to support legacy implementations. The previous version of this document required NULL to be present. If the parameters are ECParameters, then they MUST be namedCurve. The originatorKey publicKey field MUST contain the DER encoding of the value of the ASN.1 type ECPoint (see Section 7.2), which represents the sending agent's ephemeral EC public key. The ECPoint in uncompressed form MUST be supported. 🌸
  • ukm MAY be present or absent. However, message originators SHOULD include the ukm. As specified in RFC 3852 [CMS], implementations MUST support ukm message recipient processing, so interoperability is not a concern if the ukm is present or absent. The ukm is placed in the entityUInfo field of the ECC-CMS-SharedInfo structure. When present, the ukm is used to ensure that a different key-encryption key is generated, even when the ephemeral private key is improperly used more than once, by using the ECC-CMS-SharedInfo as an input to the key derivation function (see Section 7.2). 🦋
  • keyEncryptionAlgorithm MUST contain the object identifier of the key-encryption algorithm, which in this case is a key agreement algorithm (see Section 7.1.4). The parameters field contains KeyWrapAlgorithm. The KeyWrapAlgorithm is the algorithm identifier that indicates the symmetric encryption algorithm used to encrypt the content-encryption key (CEK) with the key-encryption key (KEK) and any associated parameters (see Section 7.1.5). Algorithm requirements are found in Section 8. ✨
  • recipientEncryptedKeys contains an identifier and an encrypted key for each recipient. The RecipientEncryptedKey KeyAgreeRecipientIdentifier MUST contain either the issuerAndSerialNumber identifying the recipient's certificate or the RecipientKeyIdentifier containing the subject key identifier from the recipient's certificate. In both cases, the recipient's certificate contains the recipient's static ECDH public key.

RecipientEncryptedKey EncryptedKey MUST contain the content-encryption key encrypted with the ephemeral-static, ECDH-generated pairwise key-encryption key using the algorithm specified by the KeyWrapAlgorithm. 🫶

3.1.2. Actions of the Sending Agent 🚀

when you're using ephemeral-static ECDH with EnvelopedData, the sending agent first grabs the recipient's EC public key and domain parameters (e.g., from the recipient's certificate). Then it performs one of the two ECDH variations mentioned above:

  • If the value of keyEncryptionAlgorithm indicates the use of 'standard' Diffie-Hellman, then the sending agent performs the 'Elliptic Curve Diffie-Hellman Scheme' with the 'Elliptic Curve Diffie-Hellman Primitive' in [SEC1].
  • If the value of keyEncryptionAlgorithm indicates the use of 'co-factor' Diffie-Hellman, then the sending agent performs the 'One-Pass Diffie-Hellman scheme' (method C(1, 1, ECC CDH)) in [SP800-56A].

In both of these cases, the sending agent uses the KDF defined in Section 3.6.1 of [SEC1] with the hash algorithm identified by the value of keyEncryptionAlgorithm. As a result, the sending agent obtains:

  • an ephemeral public key, which is represented as a value of the type ECPoint (see Section 7.2), encapsulated in a bit string and placed in the KeyAgreeRecipientInfo originator originatorKey publicKey field, and
  • a shared secret bit string "K", which is used as the pairwise key-encryption key for that recipient, as specified in [CMS].

In a single message, if there are multiple layers for a recipient, then the ephemeral public key can be reused by the originator for that recipient in each of the different layers. 🌈

3.1.3. Actions of the Receiving Agent 📥

when you're using ephemeral-static ECDH with EnvelopedData, the receiving agent figures out the bit string "SharedInfo", which is the DER encoding of ECC-CMS-SharedInfo (see Section 7.2), and the integer "keydatalen" from the key size, in bits, of the KeyWrapAlgorithm. It grabs the ephemeral EC public key from the bit string KeyAgreeRecipientInfo originator, with a value of the type ECPoint (see Section 7.2) encapsulated as a bit string, and, if present, the originally supplied additional user key material from the ukm field. Then it performs one of the two ECDH variations mentioned above:

  • If the value of keyEncryptionAlgorithm indicates the use of 'standard' Diffie-Hellman, then the receiving agent performs the 'Elliptic Curve Diffie-Hellman Scheme' with the 'Elliptic Curve Diffie-Hellman Primitive' in [SEC1].
  • If the value of keyEncryptionAlgorithm indicates the use of 'co-factor' Diffie-Hellman, then the receiving agent performs the 'One-Pass Diffie-Hellman scheme' (method C(1, 1, ECC CDH)) in [SP800-56A].

In both of these cases, the receiving agent uses the KDF defined in Section 3.6.1 of [SEC1] with the hash algorithm identified by the value of keyEncryptionAlgorithm. As a result, the receiving agent obtains a shared secret bit string "K", which is used as the pairwise key-encryption key to unwrap the CEK. 🔓

3.2. EnvelopedData Using 1-Pass ECMQV 💜

this section is all about how to use the 1-Pass Elliptic Curve Menezes-Qu-Vanstone (ECMQV) key agreement algorithm with EnvelopedData, method C(1, 2, ECC MQV) from [SP800-56A]. Like the KEA algorithm [CMS-KEA], 1-Pass ECMQV uses three key pairs: an ephemeral key pair, a static key pair of the sending agent, and a static key pair of the receiving agent. Using an algorithm with the sender static key pair allows for knowledge of the message creator, which means that authentication can, in some circumstances, be obtained for AuthEnvelopedData and AuthenticatedData. This means that 1-Pass ECMQV can be a common algorithm for EnvelopedData, AuthenticatedData, and AuthEnvelopedData, while ECDH can only be used in EnvelopedData. 🧚

If an implementation uses 1-Pass ECMQV with CMS EnvelopedData, then the following techniques and formats MUST be used.

The fields of EnvelopedData are as in [CMS]. As 1-Pass ECMQV is a key agreement algorithm, the RecipientInfo kari choice is used. When using 1-Pass ECMQV, the EnvelopedData originatorInfo field MAY include the certificate(s) for the EC public key(s) used in the formation of the pairwise key. ECC certificates are discussed in Section 5. 🍓

3.2.1. Fields of KeyAgreeRecipientInfo 🎀

when you're using 1-Pass ECMQV with EnvelopedData, the fields of KeyAgreeRecipientInfo are as follows:

  • version MUST be 3.
  • originator identifies the static EC public key of the sender. It SHOULD be one of the alternatives, issuerAndSerialNumber or subjectKeyIdentifier, and point to one of the sending agent's certificates.
  • ukm MUST be present. The ukm field is an octet string that MUST contain the DER encoding of the type MQVuserKeyingMaterial (see Section 7.2). The MQVuserKeyingMaterial ephemeralPublicKey algorithm field MUST contain the id-ecPublicKey object identifier (see Section 7.1.2). The parameters associated with id-ecPublicKey MUST be absent, ECParameters, or NULL. The parameters associated with id-ecPublicKey SHOULD be absent or ECParameters, as NULL is allowed to support legacy implementations. The previous version of this document required NULL to be present. If the parameters are ECParameters, then they MUST be namedCurve. The MQVuserKeyingMaterial ephemeralPublicKey publicKey field MUST contain the DER encoding of the ASN.1 type ECPoint (see Section 7.2) representing the sending agent's ephemeral EC public key. The MQVuserKeyingMaterial addedukm field, if present, contains additional user keying material from the sending agent. 🌸
  • keyEncryptionAlgorithm MUST contain the object identifier of the key-encryption algorithm, which in this case is a key agreement algorithm (see Section 7.1.4). The parameters field contains KeyWrapAlgorithm. The KeyWrapAlgorithm indicates the symmetric encryption algorithm used to encrypt the CEK with the KEK generated using the 1-Pass ECMQV algorithm and any associated parameters (see Section 7.1.5). Algorithm requirements are found in Section 8. ✨
  • recipientEncryptedKeys contains an identifier and an encrypted key for each recipient. The RecipientEncryptedKey KeyAgreeRecipientIdentifier MUST contain either the issuerAndSerialNumber identifying the recipient's certificate or the RecipientKeyIdentifier containing the subject key identifier from the recipient's certificate. In both cases, the recipient's certificate contains the recipient's static ECMQV public key.

RecipientEncryptedKey EncryptedKey MUST contain the content-encryption key encrypted with the 1-Pass ECMQV-generated pairwise key-encryption key using the algorithm specified by the KeyWrapAlgorithm. 🫶

3.2.2. Actions of the Sending Agent 🚀

when you're using 1-Pass ECMQV with EnvelopedData, the sending agent first grabs the recipient's EC public key and domain parameters (e.g., from the recipient's certificate), and checks that the domain parameters are the same as the sender's domain parameters. Next it determines an integer "keydatalen", which is the KeyWrapAlgorithm symmetric key size in bits, and also a bit string "SharedInfo", which is the DER encoding of ECC-CMS-SharedInfo (see Section 7.2). Then it performs the key deployment and key agreement operations of the Elliptic Curve MQV Scheme specified in [SP800-56A], but uses the KDF defined in Section 3.6.1 of [SEC1]. As a result, the sending agent obtains:

  • an ephemeral public key, which is represented as a value of type ECPoint (see Section 7.2), encapsulated in a bit string, placed in an MQVuserKeyingMaterial ephemeralPublicKey publicKey field (see Section 7.2), and
  • a shared secret bit string "K", which is used as the pairwise key-encryption key for that recipient, as specified in [CMS].

In a single message, if there are multiple layers for a recipient, then the ephemeral public key can be reused by the originator for that recipient in each of the different layers. 🦋

3.2.3. Actions of the Receiving Agent ✨

okay so when the receiver is handling 1-Pass ECMQV with EnvelopedData, they first work out the bit string SharedInfo, which is the DER encoding of ECC-CMS-SharedInfo (check out Section 7.2 for that one 🧚). They also figure out the integer keydatalen from the key size, in bits, of the KeyWrapAlgorithm 🔑

Then they grab the originator's static and ephemeral EC public keys from the originator and ukm fields (see Section 3.2.1 for the deets 💅), plus their own static EC public key, which is the one identified in the rid field. Before anything else, they double check that the originator's domain parameters match the recipient's domain parameters. No mismatches allowed, bestie 🙅‍♀️

Next up, they run the key agreement operation of the Elliptic Curve MQV Scheme [SP800-56A], but with a twist: they use the KDF from Section 3.6.1 of [SEC1] 🌸 The result is a shared secret bit string "K", and that's what gets used as the pairwise key-encryption key to unwrap the CEK. Iconic 👑

4. AuthenticatedData and AuthEnvelopedData Using ECC 🦋

okay this section is all about using ECC with the CMS AuthenticatedData format. Quick tea ☕: AuthenticatedData doesn't have non-repudiation, so sometimes it's the better pick over SignedData. (Like, maybe the sender doesn't want the message to be authenticated once it gets forwarded 🙈)

This section also covers using ECC with the CMS AuthEnvelopedData format [CMS-AUTHENV]. AuthEnvelopedData gives you authentication AND encryption together, which can be way more iconic than signing first and then encrypting 💜

Real talk for both AuthenticatedData and AuthEnvelopedData: data origin authentication with 1-Pass ECMQV only works when there is one and only one recipient. If there are multiple recipients, one of them can change the content and the others might not notice, and that's a known attack [BON] 😭 So a sending agent who's worried about this SHOULD use a separate AuthenticatedData or AuthEnvelopedData for each recipient 🛡️

Using an algorithm with the sender static key pair lets you know who made the message, so in some situations you can get authentication for AuthEnvelopedData and AuthenticatedData. Because of that, 1-Pass ECMQV can be the go-to algorithm across EnvelopedData, AuthenticatedData, and AuthEnvelopedData, while ECDH can only be used in EnvelopedData 💖

4.1. AuthenticatedData Using 1-Pass ECMQV 🎀

this subsection is about using the 1-Pass ECMQV key agreement algorithm with AuthenticatedData. It's method C(1, 2, ECC MQV) from [SP800-56A] ✨

When you use ECMQV with AuthenticatedData, the fields are the same as in [CMS], with a few restrictions:

  • macAlgorithm MUST contain the algorithm identifier of the message authentication code (MAC) algorithm (see Section 7.1.7). It MUST be one of these: hmac-SHA1, id-hmacWITHSHA224, id-hmacWITHSHA256, id-hmacWITHSHA384, or id-hmacWITHSHA512. 🔐
  • digestAlgorithm MUST contain the algorithm identifier of the hash algorithm (see Section 7.1.1). It MUST be one of these: id-sha1, id-sha224, id-sha256, id-sha384, or id-sha512. 🍓

Since 1-Pass ECMQV is a key agreement algorithm, the kari choice of RecipientInfo is what gets used in AuthenticatedData. When you're using 1-Pass ECMQV, the originatorInfo field MAY include the certificate(s) for the EC public key(s) used to form the pairwise key. ECC certificates get their own spotlight in Section 5 💅

4.1.1. Fields of the KeyAgreeRecipientInfo 🧁

the AuthenticatedData KeyAgreeRecipientInfo fields work exactly like the matching EnvelopedData KeyAgreeRecipientInfo fields in Section 3.2.1 of this document. Same vibes, no drama 🫶

4.1.2. Actions of the Sending Agent 📤

the sending agent does the same stuff as EnvelopedData with 1-Pass ECMQV, as laid out in Section 3.2.2 of this document ✨

Here's a fun one: in a single message, if a recipient has multiple layers, the originator can reuse the same ephemeral public key for that recipient across each of those layers. Efficient and cute 🦋

4.1.3. Actions of the Receiving Agent 📥

the receiving agent follows the same actions as EnvelopedData with 1-Pass ECMQV, as specified in Section 3.2.3 of this document 💜

4.2. AuthEnvelopedData Using 1-Pass ECMQV 🌈

this subsection covers using the 1-Pass ECMQV key agreement algorithm with AuthEnvelopedData. It's method C(1, 2, ECC MQV) from [SP800-56A] again, because it's a classic 💖

When you use ECMQV with AuthEnvelopedData, the fields are the same as in [CMS-AUTHENV] ✨

Since 1-Pass ECMQV is a key agreement algorithm, the kari choice of RecipientInfo is used. When you're using 1-Pass ECMQV, the originatorInfo field of AuthEnvelopedData MAY include the certificate(s) for the EC public key used to form the pairwise key. ECC certificates are covered in Section 5 🎀

4.2.1. Fields of the KeyAgreeRecipientInfo 🧁

the AuthEnvelopedData KeyAgreeRecipientInfo fields are used the same way as the matching EnvelopedData KeyAgreeRecipientInfo fields in Section 3.2.1 of this document. No new rules, periodt 💅

4.2.2. Actions of the Sending Agent 📤

the sending agent does the same stuff as EnvelopedData with 1-Pass ECMQV, as specified in Section 3.2.2 of this document ✨

And yep, the same ephemeral reuse trick applies: in a single message, if there are multiple layers for a recipient, the originator can reuse the ephemeral public key for that recipient in each of the layers 🦋

4.2.3. Actions of the Receiving Agent 📥

the receiving agent uses the same actions as EnvelopedData with 1-Pass ECMQV, as specified in Section 3.2.3 of this document 💜

5. Certificates Using ECC 📜

okay so Internet X.509 certificates [PKI] can totally be used with this spec to hand out agents' public keys 🔑 The use of ECC algorithms and keys inside X.509 certificates is covered in [PKI-ALG] 🌸

6. SMIMECapabilities Attribute and ECC ✨

okay bestie, this is where we tell other agents what we can do 💅 A sending agent MAY announce to receiving agents that it supports one or more of the ECC algorithms in this document, using the SMIMECapabilities signed attribute [MSG] in either a signed message or a certificate [CERTCAP] 🎀

The SMIMECapabilities attribute value shows support for one of the ECDSA signature algorithms. It's a SEQUENCE whose capabilityID is the object identifier ecdsa-with-SHA1 (with NULL parameters) or ecdsa-with-SHA*, where * is 224, 256, 384, or 512 (with absent parameters). The DER encodings are below 🧚

ecdsa-with-SHA1:   30 0b 06 07 2a 86 48 ce 3d 04 01 05 00

ecdsa-with-SHA224: 30 0a 06 08 2a 86 48 ce 3d 04 03 01

ecdsa-with-SHA256: 30 0a 06 08 2a 86 48 ce 3d 04 03 02

ecdsa-with-SHA384: 30 0a 06 08 2a 86 48 ce 3d 04 03 03

ecdsa-with-SHA512: 30 0a 06 08 2a 86 48 ce 3d 04 03 04
NOTE: the SMIMECapabilities attribute says the parameters for ECDSA with SHA-1 are NULL 🙈 but when you actually generate a digital signature, those parameters are absent. Don't mix these up, bestie!

The SMIMECapabilities attribute value can also show support for three key agreement options 🦋

  • a) the standard ECDH key agreement algorithm,
  • b) the cofactor ECDH key agreement algorithm, or
  • c) the 1-Pass ECMQV key agreement algorithm.

For each of these, it's a SEQUENCE whose capabilityID is dhSinglePass-stdDH-sha*kdf-scheme, dhSinglePass-cofactorDH-sha*kdf-scheme, or mqvSinglePass-sha*kdf-scheme respectively. Here * is 1, 224, 256, 384, or 512, and the parameters are present ✨ Those parameters name the supported key-encryption algorithm, using the KeyWrapAlgorithm algorithm identifier 💖

The DER encodings for these capabilities are below. KA means key agreement, KDF means key derivation function, and Wrap means key wrap algorithm 🌸

KA=ECDH standard KDF=SHA-1 Wrap=Triple-DES

  30 1c 06 09 2b 81 05 10 86 48 3f 00 02 30 0f 06 0b 2a 86 48 86
  f7 0d 01 09 10 03 06 05 00

KA=ECDH standard KDF=SHA-224 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0B 00 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH standard KDF=SHA-256 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0B 01 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH standard KDF=SHA-384 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0B 02 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH standard KDF=SHA-512 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0B 03 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH standard KDF=SHA-1 Wrap=AES-128

  30 18 06 09 2b 81 05 10 86 48 3f 00 02 30 0b 06 09 60 86 48 01
  65 03 04 01 05

KA=ECDH standard KDF=SHA-224 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0B 00 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH standard KDF=SHA-256 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0B 01 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH standard KDF=SHA-384 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0B 02 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH standard KDF=SHA-512 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0B 03 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH standard KDF=SHA-1 Wrap=AES-192

  30 18 06 09 2b 81 05 10 86 48 3f 00 02 30 0b 06 09 60 86 48 01
  65 03 04 01 19

KA=ECDH standard KDF=SHA-224 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0B 00 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH standard KDF=SHA-256 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0B 01 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH standard KDF=SHA-384 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0B 02 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH standard KDF=SHA-512 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0B 03 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH standard KDF=SHA-1 Wrap=AES-256

  30 18 06 09 2b 81 05 10 86 48 3f 00 02 30 0b 06 09 60 86 48 01
  65 03 04 01 2D

KA=ECDH standard KDF=SHA-224 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0B 00 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECDH standard KDF=SHA-256 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0B 01 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECDH standard KDF=SHA-384 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0B 02 30 0b 06 09 60 86 48 01 65 03 04
  01 2D 05 00

KA=ECDH standard KDF=SHA-512 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0B 03 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECDH cofactor KDF=SHA-1 Wrap=Triple-DES

  30 1c 06 09 2b 81 05 10 86 48 3f 00 03 30 0f 06 0b 2a 86 48 86
  f7 0d 01 09 10 03 06 05 00

KA=ECDH cofactor KDF=SHA-224 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0E 00 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH cofactor KDF=SHA-256 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0E 01 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH cofactor KDF=SHA-384 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0E 02 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH cofactor KDF=SHA-512 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0E 03 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECDH cofactor KDF=SHA-1 Wrap=AES-128

  30 18 06 09 2b 81 05 10 86 48 3f 00 03 30 0b 06 09 60 86 48 01
  65 03 04 01 05

KA=ECDH cofactor KDF=SHA-224 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0E 00 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH cofactor KDF=SHA-256 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0E 01 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH cofactor KDF=SHA-384 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0E 02 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH cofactor KDF=SHA-512 Wrap=AES-128

  30 17 06 06 2b 81 04 01 0E 03 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECDH cofactor KDF=SHA-1 Wrap=AES-192

  30 18 06 09 2b 81 05 10 86 48 3f 00 03 30 0b 06 09 60 86 48 01
  65 03 04 01 19

KA=ECDH cofactor KDF=SHA-224 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0E 00 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH cofactor KDF=SHA-256 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0E 01 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH cofactor KDF=SHA-384 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0E 02 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH cofactor KDF=SHA-512 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0E 03 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECDH cofactor KDF=SHA-1 Wrap=AES-256

  30 15 06 09 2b 81 05 10 86 48 3f 00 03 30 0b 06 09 60 86 48 01
  65 03 04 01 2D

KA=ECDH cofactor KDF=SHA-224 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0E 00 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECDH cofactor KDF=SHA-256 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0E 01 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECDH cofactor KDF=SHA-384 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0E 02 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECDH cofactor KDF=SHA-512 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0E 03 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECMQV 1-Pass KDF=SHA-1 Wrap=Triple-DES

  30 1c 06 09 2b 81 05 10 86 48 3f 00 10 30 0f 06 0b 2a 86 48 86
  f7 0d 01 09 10 03 06 05 00

KA=ECMQV 1-Pass KDF=SHA-224 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0F 00 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECMQV 1-Pass KDF=SHA-256 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0F 01 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECMQV 1-Pass KDF=SHA-384 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0F 02 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECMQV 1-Pass KDF=SHA-512 Wrap=Triple-DES

  30 17 06 06 2b 81 04 01 0F 03 30 0d 06 0b 2a 86 48 86 f7 0d 01
  09 10 03 06

KA=ECMQV 1-Pass KDF=SHA-1 Wrap=AES-128

  30 18 06 09 2b 81 05 10 86 48 3f 00 10 30 0b 06 09 60 86 48 01
  65 03 04 01 05

KA=ECMQV 1-Pass KDF=SHA-224 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0F 00 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECMQV 1-Pass KDF=SHA-256 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0F 01 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECMQV 1-Pass KDF=SHA-384 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0F 02 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECMQV 1-Pass KDF=SHA-512 Wrap=AES-128

  30 15 06 06 2b 81 04 01 0F 03 30 0b 06 09 60 86 48 01 65 03 04
  01 05

KA=ECMQV 1-Pass KDF=SHA-1 Wrap=AES-192

  30 18 06 09 2b 81 05 10 86 48 3f 00 10 30 0b 06 09 60 86 48 01
  65 03 04 01 19

KA=ECMQV 1-Pass KDF=SHA-224 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0F 00 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECMQV 1-Pass KDF=SHA-256 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0F 01 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECMQV 1-Pass KDF=SHA-384 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0F 02 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECMQV 1-Pass KDF=SHA-512 Wrap=AES-192

  30 15 06 06 2b 81 04 01 0F 03 30 0b 06 09 60 86 48 01 65 03 04
  01 19

KA=ECMQV 1-Pass KDF=SHA-1 Wrap=AES-256

  30 18 06 09 2b 81 05 10 86 48 3f 00 10 30 0b 06 09 60 86 48 01
  65 03 04 01 2D

KA=ECMQV 1-Pass KDF=SHA-224 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0F 00 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECMQV 1-Pass KDF=SHA-256 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0F 01 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECMQV 1-Pass KDF=SHA-384 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0F 02 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

KA=ECMQV 1-Pass KDF=SHA-512 Wrap=AES-256

  30 15 06 06 2b 81 04 01 0F 03 30 0b 06 09 60 86 48 01 65 03 04
  01 2D

🌈 NOTE: the S/MIME Capabilities for the supported AES content-encryption key sizes are defined in [CMS-AES]. And the ones for the supported MAC algorithms live in [CMS-ASN] 💜

7. ASN.1 Syntax 📜

here's all the ASN.1 syntax [X.680], [X.681], [X.682], [X.683] used in this document, gathered in one place so it's easy to find 🍓

7.1. Algorithm Identifiers

this section has the object identifiers for the algorithms used in this document, plus any parameters they come with 🔥

7.1.1. Digest Algorithms

digest algorithm object identifiers show up in the digestAlgorithms and digestAlgorithm fields of SignedData, and in the digestAlgorithm field of AuthenticatedData. The digest algorithms used here are SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512 ✨ Their object identifiers and parameters are in [CMS-ALG] and [CMS-SHA2] 💅

7.1.2. Originator Public Key 🔑✨

okay so the KeyAgreeRecipientInfo originator field uses this object identifier to say "hey, this is an elliptic curve public key" 💅

id-ecPublicKey OBJECT IDENTIFIER ::= {
  ansi-x9-62 keyType(2) 1 }

where

ansi-x9-62 OBJECT IDENTIFIER ::= {
  iso(1) member-body(2) us(840) 10045 }

when id-ecPublicKey shows up with an algorithm identifier, its parameters MUST be either absent or ECParameters 🫶 Implementations MUST accept id-ecPublicKey with absent and ECParameters parameters, no exceptions bestie 🙈 If ECParameters is present, its value MUST match the recipient's ECParameters. And implementations SHOULD generate absent parameters for id-ecPublicKey in the KeyAgreeRecipientInfo originator field, because that's the vibe 🌸

[CMS-ECC] had the parameters as NULL. Support for that legacy form is OPTIONAL 🎀

7.1.3. Signature Algorithms ✍️💖

Signature algorithm identifiers are used in the SignedData signatureAlgorithm and signature fields. The signature algorithms in this document are ECDSA with SHA-1, ECDSA with SHA-224, ECDSA with SHA-256, ECDSA with SHA-384, and ECDSA with SHA-512 🌈 The object identifiers and parameters for these are in [PKI-ALG], so go check there 💜

Same deal as before: [CMS-ECC] had NULL parameters, and support for that legacy form is OPTIONAL ✨

7.1.4. Key Agreement Algorithms 🤝🦋

Key agreement algorithms show up in EnvelopedData, AuthenticatedData, and AuthEnvelopedData, inside the KeyAgreeRecipientInfo keyEncryptionAlgorithm field. These object identifiers name the key agreement algorithms used in this document [SP800-56A], [SEC1] 👑

dhSinglePass-stdDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
  x9-63-scheme 2 }

dhSinglePass-stdDH-sha224kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 0 }

dhSinglePass-stdDH-sha256kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 1 }

dhSinglePass-stdDH-sha384kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 2 }

dhSinglePass-stdDH-sha512kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 3 }

dhSinglePass-cofactorDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
  x9-63-scheme 3 }

dhSinglePass-cofactorDH-sha224kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 0 }

dhSinglePass-cofactorDH-sha256kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 1 }

dhSinglePass-cofactorDH-sha384kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 2 }

dhSinglePass-cofactorDH-sha512kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 3 }

mqvSinglePass-sha1kdf-scheme OBJECT IDENTIFIER ::= {
  x9-63-scheme 16 }

mqvSinglePass-sha224kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 0 }

mqvSinglePass-sha256kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 1 }

mqvSinglePass-sha384kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 2 }

mqvSinglePass-sha512kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 3 }

where

x9-63-scheme OBJECT IDENTIFIER ::= {
  iso(1) identified-organization(3) tc68(133) country(16)
  x9(840) x9-63(63) schemes(0) }

and

secg-scheme OBJECT IDENTIFIER ::= {
  iso(1) identified-organization(3) certicom(132) schemes(1) }

When these object identifiers are used within an algorithm identifier, the associated parameters field holds a KeyWrapAlgorithm, which tells you the key wrap algorithm and any parameters it needs 🎁

7.1.5. Key Wrap Algorithms 🎀🔐

Key wrap algorithms are used as part of the parameters in the key agreement algorithm. The key wrap algorithms in this document are Triple-DES, AES-128, AES-192, and AES-256 💅 The object identifiers and parameters for these are in [CMS-ALG] and [CMS-AES] 📚

7.1.6. Content Encryption Algorithms 🍓💜

Content encryption algorithms are used in EnvelopedData and AuthEnvelopedData, in the EncryptedContentInfo contentEncryptionAlgorithm field 🫧

With EnvelopedData, the content encryption algorithms are 3-Key Triple DES in CBC mode, AES-128 in CBC mode, AES-192 in CBC mode, and AES-256 in CBC mode.

With AuthEnvelopedData, the content encryption algorithms are AES-128 in CCM mode, AES-192 in CCM mode, AES-256 in CCM mode, AES-128 in GCM mode, AES-192 in GCM mode, and AES-256 in GCM mode 🦋

The object identifiers and parameters for the EnvelopedData algorithms are in [CMS-ALG] and [CMS-AES]. For the AuthEnvelopedData ones, look in [CMS-AESCG] ✨

7.1.7. Message Authentication Code Algorithms 🔏🌸

Message authentication code algorithms are used in AuthenticatedData, in the macAlgorithm field. The ones in this document are HMAC with SHA-1, HMAC with SHA-224, HMAC with SHA-256, HMAC with SHA-384, and HMAC with SHA-512 💖 Their object identifiers and parameters are in [CMS-ALG] and [HMAC-SHA2].

NOTE: [HMAC-SHA2] defines the object identifiers for HMAC with SHA-224, HMAC with SHA-256, HMAC with SHA-384, and HMAC with SHA-512, but there is no ASN.1 module to import these object identifiers from. So the object identifiers for these algorithms are included in the ASN.1 modules in Appendix A 🙈

7.1.8. Key Derivation Algorithm 🧮⭐

The KDF used in this document is the one specified in Section 3.6.1 of [SEC1] 🫶 The hash algorithm is identified in the key agreement algorithm. For example, dhSinglePass-stdDH-sha256kdf-scheme uses the KDF from [SEC1] but uses SHA-256 instead of SHA-1 🌈

7.2. Other Syntax 🧸💫

Here's some additional syntax used in this document, bestie 💕

When you're using ECDSA with SignedData, ECDSA signatures are encoded using this type:

ECDSA-Sig-Value ::= SEQUENCE {
  r INTEGER,
  s INTEGER }

ECDSA-Sig-Value is specified in [PKI-ALG]. Within CMS, it gets DER-encoded and placed within a signature field of SignedData 🔥

When you're using ECDH and ECMQV with EnvelopedData, AuthenticatedData, and AuthEnvelopedData, the ephemeral and static public keys are encoded using the type ECPoint. Implementations MUST support uncompressed keys, MAY support compressed keys, and MUST NOT support hybrid keys 👑 Not me saying hybrid keys are a no-go, but the spec literally says MUST NOT, so 💀

ECPoint ::= OCTET STRING

When you're using ECMQV with EnvelopedData, AuthenticatedData, and AuthEnvelopedData, the sending agent's ephemeral public key and additional keying material are encoded using this type:

MQVuserKeyingMaterial ::= SEQUENCE {
  ephemeralPublicKey      OriginatorPublicKey,
  addedukm            [0] EXPLICIT UserKeyingMaterial OPTIONAL  }

The ECPoint syntax is used to represent the ephemeral public key, and that goes in the ephemeralPublicKey publicKey field. The additional user keying material goes in the addedukm field. Then the MQVuserKeyingMaterial value is DER-encoded and placed within the ukm field of EnvelopedData, AuthenticatedData, or AuthEnvelopedData 🧚

When you're using ECDH or ECMQV with EnvelopedData, AuthenticatedData, or AuthEnvelopedData, the key-encryption keys are derived using this type:

ECC-CMS-SharedInfo ::= SEQUENCE {
  keyInfo         AlgorithmIdentifier,
  entityUInfo [0] EXPLICIT OCTET STRING OPTIONAL,
  suppPubInfo [2] EXPLICIT OCTET STRING  }

Here's what each ECC-CMS-SharedInfo field does 🦄

  • keyInfo holds the object identifier of the key-encryption algorithm (the one used to wrap the CEK) plus its parameters. In this spec, 3DES wrap has NULL parameters, while the AES wraps have absent parameters.
  • entityUInfo optionally holds additional keying material from the sending agent. With ECDH and CMS, this field holds the octet string ukm. With ECMQV and CMS, it holds the octet string addedukm (encoded in MQVuserKeyingMaterial).
  • suppPubInfo holds the length of the generated KEK, in bits, as a 32-bit number, same as in [CMS-DH] and [CMS-AES]. For example, for AES-256 it would be 00 00 01 00 🌟

Within CMS, ECC-CMS-SharedInfo gets DER-encoded and used as input to the key derivation function, as specified in Section 3.6.1 of [SEC1] 💜

NOTE: ECC-CMS-SharedInfo differs from the OtherInfo specified in [CMS-DH]. Here, a counter value is NOT included in the keyInfo field, because the key derivation function from Section 3.6.1 of [SEC1] already makes sure there's enough keying data. Lowkey clever, no cap 🧠✨

okay bestie, let's talk about which algorithms and curves to pick 💅. It is RECOMMENDED that implementations of this spec support SignedData and EnvelopedData 💖. Supporting AuthenticatedData and AuthEnvelopedData is OPTIONAL, so no pressure 🦋.

To keep things interoperable (the whole point 🫶), implementations SHOULD use the elliptic curve domain parameters specified by [PKI-ALG].

Implementations that support SignedData with ECDSA:

  • MUST support ECDSA with SHA-256; and
  • MAY support ECDSA with SHA-1, ECDSA with SHA-224, ECDSA with SHA-384, and ECDSA with SHA-512; other digital signature algorithms MAY also be supported.

When using ECDSA, to promote interoperability it is RECOMMENDED that the P-192, P-224, and P-256 curves be used with SHA-256; the P-384 curve be used with SHA-384; and the P-521 curve be used with SHA-512 🌸.

If EnvelopedData is supported, then the ephemeral-static ECDH standard primitive MUST be supported 🔥. Support for the ephemeral-static ECDH cofactor is OPTIONAL, and support for 1-Pass ECMQV is also OPTIONAL 🎀.

Implementations that support EnvelopedData with the ephemeral-static ECDH standard primitive:

  • MUST support the dhSinglePass-stdDH-sha256kdf-scheme key agreement algorithm, the id-aes128-wrap key wrap algorithm, and the id-aes128-cbc content encryption algorithm; and
  • MAY support the dhSinglePass-stdDH-sha1kdf-scheme, dhSinglePass-stdDH-sha224kdf-scheme, dhSinglePass-stdDH-sha384kdf-scheme, and dhSinglePass-stdDH-sha512kdf-scheme key agreement algorithms; the id-alg-CMS3DESwrap, id-aes192-wrap, and id-aes256-wrap key wrap algorithms; and the des-ede3-cbc, id-aes192-cbc, and id-aes256-cbc content encryption algorithms; other algorithms MAY also be supported.

Implementations that support EnvelopedData with the ephemeral-static ECDH cofactor primitive:

  • MUST support the dhSinglePass-cofactorDH-sha256kdf-scheme key agreement algorithm, the id-aes128-wrap key wrap algorithm, and the id-aes128-cbc content encryption algorithm; and
  • MAY support the dhSinglePass-cofactorDH-sha1kdf-scheme, dhSinglePass-cofactorDH-sha224kdf-scheme, dhSinglePass-cofactorDH-sha384kdf-scheme, and dhSinglePass-cofactorDH-sha512kdf-scheme key agreement algorithms; the id-alg-CMS3DESwrap, id-aes192-wrap, and id-aes256-wrap key wrap algorithms; and the des-ede3-cbc, id-aes192-cbc, and id-aes256-cbc content encryption algorithms; other algorithms MAY also be supported.

Implementations that support EnvelopedData with 1-Pass ECMQV:

  • MUST support the mqvSinglePass-sha256kdf-scheme key agreement algorithm, the id-aes128-wrap key wrap algorithm, and the id-aes128-cbc content encryption algorithm; and
  • MAY support the mqvSinglePass-sha1kdf-scheme, mqvSinglePass-sha224kdf-scheme, mqvSinglePass-sha384kdf-scheme, and mqvSinglePass-sha512kdf-scheme key agreement algorithms; the id-alg-CMS3DESwrap, id-aes192-wrap, and id-aes256-wrap key wrap algorithms; and the des-ede3-cbc, id-aes192-cbc, and id-aes256-cbc content encryption algorithms; other algorithms MAY also be supported.

Implementations that support AuthenticatedData with 1-Pass ECMQV:

  • MUST support the mqvSinglePass-sha256kdf-scheme key agreement, the id-aes128-wrap key wrap, the id-sha256 message digest, and id-hmacWithSHA256 message authentication code algorithms; and
  • MAY support the mqvSinglePass-sha1kdf-scheme, mqvSinglePass-sha224kdf-scheme, mqvSinglePass-sha384kdf-scheme, mqvSinglePass-sha512kdf-scheme key agreement algorithms; the id-alg-CMS3DESwrap, id-aes192-wrap, and id-aes256-wrap key wrap algorithms; the id-sha1, id-sha224, id-sha384, and id-sha512 message digest algorithms; and the hmac-SHA1, id-hmacWithSHA224, id-hmacWithSHA384, and id-hmacWithSHA512 message authentication code algorithms; other algorithms MAY also be supported.

Implementations that support AuthEnvelopedData with 1-Pass ECMQV:

  • MUST support the mqvSinglePass-sha256kdf-scheme key agreement, the id-aes128-wrap key wrap, and the id-aes128-ccm authenticated-content encryption; and
  • MAY support the mqvSinglePass-sha1kdf-scheme, mqvSinglePass-sha224kdf-scheme, mqvSinglePass-sha384kdf-scheme, and mqvSinglePass-sha512kdf-scheme key agreement algorithms; the id-alg-CMS3DESwrap, id-aes192-wrap, and id-aes256-wrap key wrap algorithms; and the id-aes192-ccm, id-aes256-ccm, id-aes128-gcm, id-aes192-gcm, and id-aes256-ccm authenticated-content encryption algorithms; other algorithms MAY also be supported 🧚

9. Security Considerations 💅

Okay bestie, this part is SERIOUS 😭 so listen up. Cryptographic algorithms will get broken or weakened over time, so implementers and users need to check that the algorithms in this document still give the level of security they expect 🔐. The IETF may put out documents from time to time about the current state of the art ✨.

Cryptographic algorithms rely on random numbers 🎲. See [RANDOM] for guidance on generating random numbers, no skipping this one 🙈.

Receiving agents that validate signatures, and sending agents that encrypt messages, need to be cautious about cryptographic processing when they use keys larger than those mandated in this specification 🚨. An attacker could send keys, or certificates with keys, that cause excessive cryptographic processing, for example keys larger than those mandated in this specification, and that could swamp the processing element 💀. Agents that use such keys without first validating the certificate to a trust anchor are advised to have some sort of cryptographic resource management system to prevent these attacks 🛡️.

Using secret keys of an appropriate size is crucial to the security of a Diffie-Hellman exchange 🔑. For elliptic curve groups, the size of the secret key must be equal to the size of n (the order of the group generated by the point g). Using larger secret keys provides absolutely no additional security, and using smaller secret keys is likely to result in dramatically less security 😭. (See [SP800-56A] for more information on selecting secret keys.)

This specification is based on [CMS], [CMS-AES], [CMS-AESCG], [CMS-ALG], [CMS-AUTHENV], [CMS-DH], [CMS-SHA2], [FIPS180-3], [FIPS186-3], and [HMAC-SHA2], and the appropriate security considerations of those documents apply 📚.

In addition, implementers of AuthenticatedData and AuthEnvelopedData should be aware of the concerns expressed in [BON] when using AuthenticatedData and AuthEnvelopedData to send messages to more than one recipient 👀. Also, users of MQV should be aware of the vulnerability described in [K] 🫶.

When implementing EnvelopedData, AuthenticatedData, and AuthEnvelopedData, there are five algorithm-related choices that need to be made:

  1. What is the public key size?
  2. What is the KDF?
  3. What is the key wrap algorithm?
  4. What is the content encryption algorithm?
  5. What is the curve?

Consideration must be given to the strength of the security provided by each of these choices 💅. Security algorithm strength is measured in bits, where bits is measured in equivalence to a symmetric cipher algorithm. Thus, a strong symmetric cipher algorithm with a key of X bits is said to provide X bits of security. For other algorithms, the key size is mapped to an equivalent symmetric cipher strength 🧮. It is recommended that the bits of security provided by each are roughly equivalent. The following table provides comparable minimum bits of security [SP800-57] for the ECDH/ECMQV key sizes, KDFs, key wrapping algorithms, and content encryption algorithms. It also lists curves [PKI-ALG] for the key sizes 🌈.

Minimum  | ECDH or  | Key        | Key      | Content     | Curves
Bits of  | ECMQV    | Derivation | Wrap     | Encryption  |
Security | Key Size | Function   | Alg.     | Alg.        |
---------+----------+------------+----------+-------------+----------
80       | 160-223  | SHA-1      | 3DES     | 3DES CBC    | sect163k1
         |          | SHA-224    | AES-128  | AES-128 CBC | secp163r2
         |          | SHA-256    | AES-192  | AES-192 CBC | secp192r1
         |          | SHA-384    | AES-256  | AES-256 CBC |
         |          | SHA-512    |          |             |
---------+----------+------------+----------+-------------+---------
112      | 224-255  | SHA-1      | 3DES     | 3DES CBC    | secp224r1
         |          | SHA-224    | AES-128  | AES-128 CBC | sect233k1
         |          | SHA-256    | AES-192  | AES-192 CBC | sect233r1
         |          | SHA-384    | AES-256  | AES-256 CBC |
         |          | SHA-512    |          |             |
---------+----------+------------+----------+-------------+---------
128      | 256-383  | SHA-1      | AES-128  | AES-128 CBC | secp256r1
         |          | SHA-224    | AES-192  | AES-192 CBC | sect283k1
         |          | SHA-256    | AES-256  | AES-256 CBC | sect283r1
         |          | SHA-384    |          |             |
         |          | SHA-512    |          |             |
---------+----------+------------+----------+-------------+---------
192      | 384-511  | SHA-224    | AES-192  | AES-192 CBC | secp384r1
         |          | SHA-256    | AES-256  | AES-256 CBC | sect409k1
         |          | SHA-384    |          |             | sect409r1
         |          | SHA-512    |          |             |
---------+----------+------------+----------+-------------+---------
256      | 512+     | SHA-256    | AES-256  | AES-256 CBC | secp521r1
         |          | SHA-384    |          |             | sect571k1
         |          | SHA-512    |          |             | sect571r1
---------+----------+------------+----------+-------------+---------

To promote interoperability, the following choices are RECOMMENDED 🎀:

Minimum  | ECDH or  | Key        | Key      | Content     | Curve
Bits of  | ECMQV    | Derivation | Wrap     | Encryption  |
Security | Key Size | Function   | Alg.     | Alg.        |
---------+----------+------------+----------+-------------+----------
80       | 192      | SHA-256    | 3DES     | 3DES CBC    | secp192r1
---------+----------+------------+----------+-------------+----------
112      | 224      | SHA-256    | 3DES     | 3DES CBC    | secp224r1
---------+----------+------------+----------+-------------+----------
128      | 256      | SHA-256    | AES-128  | AES-128 CBC | secp256r1
---------+----------+------------+----------+-------------+----------
192      | 384      | SHA-384    | AES-256  | AES-256 CBC | secp384r1
---------+----------+------------+----------+-------------+----------
256      | 512+     | SHA-512    | AES-256  | AES-256 CBC | secp521r1
---------+----------+------------+----------+-------------+----------

When implementing SignedData, there are three algorithm-related choices that need to be made:

  1. What is the public key size?
  2. What is the hash algorithm?
  3. What is the curve?

Consideration must be given to the bits of security provided by each of these choices 💖. Security is measured in bits, where a strong symmetric cipher with a key of X bits is said to provide X bits of security. It is recommended that the bits of security provided by each choice are roughly equivalent. The following table provides comparable minimum bits of security [SP800-57] for the ECDSA key sizes and message digest algorithms. It also lists curves [PKI-ALG] for the key sizes ✨.

Minimum  | ECDSA    | Message   | Curve
Bits of  | Key Size | Digest    |
Security |          | Algorithm |
---------+----------+-----------+-----------
80       | 160-223  | SHA-1     | sect163k1
         |          | SHA-224   | secp163r2
         |          | SHA-256   | secp192r1
         |          | SHA-384   |
         |          | SHA-512   |
---------+----------+-----------+-----------
112      | 224-255  | SHA-224   | secp224r1
         |          | SHA-256   | sect233k1
         |          | SHA-384   | sect233r1
         |          | SHA-512   |
---------+----------+-----------+-----------
128      | 256-383  | SHA-256   | secp256r1
         |          | SHA-384   | sect283k1
         |          | SHA-512   | sect283r1
---------+----------+-----------+-----------
192      | 384-511  | SHA-384   | secp384r1
         |          | SHA-512   | sect409k1
         |          |           | sect409r1
---------+----------+-----------+-----------
256      | 512+     | SHA-512   | secp521r1
         |          |           | sect571k1
         |          |           | sect571r1
---------+----------+-----------+-----------

To promote interoperability, the following choices are RECOMMENDED 🌸:

Minimum  | ECDSA    | Message   | Curve
Bits of  | Key Size | Digest    |
Security |          | Algorithm |
---------+----------+-----------+-----------
80       | 192      | SHA-256   | sect192r1
---------+----------+-----------+-----------
112      | 224      | SHA-256   | secp224r1
---------+----------+-----------+-----------
128      | 256      | SHA-256   | secp256r1
---------+----------+-----------+-----------
192      | 384      | SHA-384   | secp384r1
---------+----------+-----------+-----------
256      | 512+     | SHA-512   | secp521r1
---------+----------+-----------+-----------

10. IANA Considerations 🦋

This document makes extensive use of object identifiers to register originator public key types and algorithms 🧚. The algorithm object identifiers are registered in the ANSI X9.62, ANSI X9.63, NIST, RSA, and SECG arcs. Additionally, object identifiers are used to identify the ASN.1 modules found in Appendix A (there are two). These are defined by the SMIME WG Registrar in an arc delegated by RSA to the SMIME Working Group:

iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0)

No action by IANA is necessary for this document or any anticipated updates 💜.

11. References 🌈

11.1. Normative References 📚✨

okay bestie, these are the must-read ones 🫶 Everything below is listed exactly as the original gives it, so you can look up any of them.

[CMS] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 5652, September 2009.

[CMS-AES] Schaad, J., "Use of the Advanced Encryption Standard (AES) Encryption Algorithm in Cryptographic Message Syntax (CMS)", RFC 3565, July 2003.

[CMS-AESCG] Housley, R., "Using AES-CCM and AES-GCM Authenticated Encryption in the Cryptographic Message Syntax (CMS)", RFC 5084, December 2007.

[CMS-ALG] Housley, R., "Cryptographic Message Syntax (CMS) Algorithms", RFC 3370, August 2002.

[CMS-AUTHENV] Housley, R., "Cryptographic Message Syntax (CMS) Authenticated-Enveloped-Data Content Type", RFC 5083, November 2007.

[CMS-DH] Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC 2631, June 1999.

[CMS-SHA2] Turner, S., "Using SHA2 Algorithms with Cryptographic Message Syntax", RFC 5754, January 2010.

[FIPS180-3] National Institute of Standards and Technology (NIST), FIPS Publication 180-3: Secure Hash Standard, October 2008.

[FIPS186-3] National Institute of Standards and Technology (NIST), FIPS Publication 186-3: Digital Signature Standard, June 2009.

[HMAC-SHA2] Nystrom, M., "Identifiers and Test Vectors for HMAC-SHA-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512", RFC 4231, December 2005.

[MUST] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[MSG] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification", RFC 5751, January 2010.

[PKI] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008.

[PKI-ALG] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk, "Elliptic Curve Cryptography Subject Public Key Information", RFC 5480, March 2009.

[RANDOM] Eastlake, D., 3rd, Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005.

[RSAOAEP] Schaad, J., Kaliski, B., and R. Housley, "Additional Algorithms and Identifiers for RSA Cryptography for use in the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 4055, June 2005.

[SEC1] Standards for Efficient Cryptography Group, "SEC 1: Elliptic Curve Cryptography", version 2.0, May 2009, available from www.secg.org.

[SP800-56A] National Institute of Standards and Technology (NIST), Special Publication 800-56A: Recommendation Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised), March 2007.

[X.680] ITU-T Recommendation X.680 (2002) | ISO/IEC 8824-1:2002. Information Technology - Abstract Syntax Notation One.

11.2. Informative References 🦋

ooh, these are the extra-credit reads 💅 Still the same exact details, just chillier vibes.

[BON] D. Boneh, "The Security of Multicast MAC", Presentation at Selected Areas of Cryptography 2000, Center for Applied Cryptographic Research, University of Waterloo, 2000. Paper version available from http://crypto.stanford.edu/~dabo/papers/mmac.ps

[CERTCAP] Santesson, S., "X.509 Certificate Extension for Secure/Multipurpose Internet Mail Extensions (S/MIME) Capabilities", RFC 4262, December 2005.

[CMS-ASN] Hoffman, P. and J. Schaad, "New ASN.1 Modules for CMS and S/MIME", Work in Progress, August 2009.

[CMS-ECC] Blake-Wilson, S., Brown, D., and P. Lambert, "Use of Elliptic Curve Cryptography (ECC) Algorithms in Cryptographic Message Syntax (CMS)", RFC 3278, April 2002.

[CMS-KEA] Pawling, J., "Use of the KEA and SKIPJACK Algorithms in CMS", RFC 2876, July 2000.

[K] B. Kaliski, "MQV Vulnerability", Posting to ANSI X9F1 and IEEE P1363 newsgroups, 1998.

[PKI-ASN] Hoffman, P. and J. Schaad, "New ASN.1 Modules for PKIX", Work in Progress, August 2009.

[SP800-57] National Institute of Standards and Technology (NIST), Special Publication 800-57: Recommendation for Key Management - Part 1 (Revised), March 2007.

[X.681] ITU-T Recommendation X.681 (2002) | ISO/IEC 8824-2:2002. Information Technology - Abstract Syntax Notation One: Information Object Specification.

[X.682] ITU-T Recommendation X.682 (2002) | ISO/IEC 8824-3:2002. Information Technology - Abstract Syntax Notation One: Constraint Specification.

[X.683] ITU-T Recommendation X.683 (2002) | ISO/IEC 8824-4:2002. Information Technology - Abstract Syntax Notation One: Parameterization of ASN.1 Specifications, 2002.

[X9.62] X9.62-2005, "Public Key Cryptography for the Financial Services Industry: The Elliptic Curve Digital Signature Standard (ECDSA)", November, 2005.

Appendix A. ASN.1 Modules ✨

Appendix A.1 provides the normative ASN.1 definitions for the structures described in this specification using ASN.1 as defined in [X.680] for compilers that support the 1988 ASN.1.

Appendix A.2 provides informative ASN.1 definitions for the structures described in this specification using ASN.1 as defined in [X.680], [X.681], [X.682], and [X.683] for compilers that support the 2002 ASN.1. This appendix contains the same information as Appendix A.1 in a more recent (and precise) ASN.1 notation; however, Appendix A.1 takes precedence in case of conflict. 🌸

Appendix A. ASN.1 Modules 🎀

okay bestie, the ASN.1 modules are here and they're literally the receipts 🧚 first up is the 1988 version 💅

A.1. 1988 ASN.1 Module

   CMSECCAlgs-2009-88
     { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
       smime(16) modules(0) id-mod-cms-ecc-alg-2009-88(45) }

   DEFINITIONS IMPLICIT TAGS ::=

   BEGIN

   -- EXPORTS ALL

   IMPORTS

   -- From [PKI]

   AlgorithmIdentifier
     FROM PKIX1Explicit88
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7) mod(0)
         pkix1-explicit(18) }

   -- From [RSAOAEP]

   id-sha224, id-sha256, id-sha384, id-sha512
     FROM PKIX1-PSS-OAEP-Algorithms
       { iso(1) identified-organization(3) dod(6) internet(1)
         security(5) mechanisms(5) pkix(7) id-mod(0)
         id-mod-pkix1-rsa-pkalgs(33) }

   -- From [PKI-ALG]

   id-sha1, ecdsa-with-SHA1, ecdsa-with-SHA224,
   ecdsa-with-SHA256, ecdsa-with-SHA384, ecdsa-with-SHA512,
   id-ecPublicKey, ECDSA-Sig-Value, ECPoint, ECParameters
     FROM PKIX1Algorithms2008
       { iso(1) identified-organization(3) dod(6) internet(1)
         security(5) mechanisms(5) pkix(7) id-mod(0) 45 }

   -- From [CMS]

   OriginatorPublicKey, UserKeyingMaterial
     FROM CryptographicMessageSyntax2004
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
         smime(16) modules(0) cms-2004(24) }

   -- From [CMS-ALG]

   hMAC-SHA1, des-ede3-cbc, id-alg-CMS3DESwrap, CBCParameter
     FROM CryptographicMessageSyntaxAlgorithms
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
         smime(16) modules(0) cmsalg-2001(16) }

   -- From [CMS-AES]

   id-aes128-CBC, id-aes192-CBC, id-aes256-CBC, AES-IV,
   id-aes128-wrap, id-aes192-wrap, id-aes256-wrap
     FROM CMSAesRsaesOaep
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
         smime(16) modules(0) id-mod-cms-aes(19) }

   -- From [CMS-AESCG]

   id-aes128-CCM, id-aes192-CCM, id-aes256-CCM, CCMParameters
   id-aes128-GCM, id-aes192-GCM, id-aes256-GCM, GCMParameters
     FROM CMS-AES-CCM-and-AES-GCM
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
         smime(16) modules(0) id-mod-cms-aes(32) }

   ;

   --
   -- Message Digest Algorithms: Imported from [PKI-ALG] and [RSAOAEP]
   --

   -- id-sha1 Parameters are preferred absent
   -- id-sha224 Parameters are preferred absent
   -- id-sha256 Parameters are preferred absent
   -- id-sha384 Parameters are preferred absent
   -- id-sha512 Parameters are preferred absent

   --
   -- Signature Algorithms: Imported from [PKI-ALG]
   --

   -- ecdsa-with-SHA1 Parameters are NULL
   -- ecdsa-with-SHA224 Parameters are absent
   -- ecdsa-with-SHA256 Parameters are absent
   -- ecdsa-with-SHA384 Parameters are absent
   -- ecdsa-with-SHA512 Parameters are absent

   -- ECDSA Signature Value
   -- Contents of SignatureValue OCTET STRING

   -- ECDSA-Sig-Value ::= SEQUENCE {
   --   r  INTEGER,
   --   s  INTEGER
   -- }

   --
   -- Key Agreement Algorithms
   --

   x9-63-scheme OBJECT IDENTIFIER ::= {
     iso(1) identified-organization(3) tc68(133) country(16) x9(840)
     x9-63(63) schemes(0) }
   secg-scheme OBJECT IDENTIFIER ::= {
     iso(1) identified-organization(3) certicom(132) schemes(1) }

   --
   -- Diffie-Hellman Single Pass, Standard, with KDFs
   --

   -- Parameters are always present and indicate the key wrap algorithm
   -- with KeyWrapAlgorithm.

   dhSinglePass-stdDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
     x9-63-scheme 2 }

   dhSinglePass-stdDH-sha224kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 11 0 }

   dhSinglePass-stdDH-sha256kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 11 1 }

   dhSinglePass-stdDH-sha384kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 11 2 }

   dhSinglePass-stdDH-sha512kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 11 3 }

   --
   -- Diffie-Hellman Single Pass, Cofactor, with KDFs
   --

   dhSinglePass-cofactorDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
     x9-63-scheme 3 }

   dhSinglePass-cofactorDH-sha224kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 14 0 }

   dhSinglePass-cofactorDH-sha256kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 14 1 }

   dhSinglePass-cofactorDH-sha384kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 14 2 }

   dhSinglePass-cofactorDH-sha512kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 14 3 }

   --
   -- MQV Single Pass, Cofactor, with KDFs
   --

   mqvSinglePass-sha1kdf-scheme OBJECT IDENTIFIER ::= {
     x9-63-scheme 16 }

   mqvSinglePass-sha224kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 15 0 }

   mqvSinglePass-sha256kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 15 1 }

   mqvSinglePass-sha384kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 15 2 }

   mqvSinglePass-sha512kdf-scheme OBJECT IDENTIFIER ::= {
     secg-scheme 15 3 }

   --
   -- Key Wrap Algorithms: Imported from [CMS-ALG] and [CMS-AES]
   --
   KeyWrapAlgorithm ::= AlgorithmIdentifier

   -- id-alg-CMS3DESwrap Parameters are NULL
   -- id-aes128-wrap Parameters are absent
   -- id-aes192-wrap Parameters are absent
   -- id-aes256-wrap Parameters are absent

   --
   -- Content Encryption Algorithms: Imported from [CMS-ALG]
   -- and [CMS-AES]
   --

   -- des-ede3-cbc Parameters are CBCParameter
   -- id-aes128-CBC Parameters are AES-IV
   -- id-aes192-CBC Parameters are AES-IV
   -- id-aes256-CBC Parameters are AES-IV
   -- id-aes128-CCM Parameters are CCMParameters
   -- id-aes192-CCM Parameters are CCMParameters
   -- id-aes256-CCM Parameters are CCMParameters
   -- id-aes128-GCM Parameters are GCMParameters
   -- id-aes192-GCM Parameters are GCMParameters
   -- id-aes256-GCM Parameters are GCMParameters

   --
   -- Message Authentication Code Algorithms
   --

   -- hMAC-SHA1 Parameters are preferred absent

   -- HMAC with SHA-224, SHA-256, SHA_384, and SHA-512 Parameters are
   -- absent

   id-hmacWithSHA224 OBJECT IDENTIFIER ::= {
     iso(1) member-body(2) us(840) rsadsi(113549)
     digestAlgorithm(2) 8 }

   id-hmacWithSHA256 OBJECT IDENTIFIER ::= {
     iso(1) member-body(2) us(840) rsadsi(113549)
     digestAlgorithm(2) 9 }

   id-hmacWithSHA384 OBJECT IDENTIFIER ::= {
     iso(1) member-body(2) us(840) rsadsi(113549)
     digestAlgorithm(2) 10 }

   id-hmacWithSHA512 OBJECT IDENTIFIER ::= {
     iso(1) member-body(2) us(840) rsadsi(113549)
     digestAlgorithm(2) 11 }

   --
   -- Originator Public Key Algorithms: Imported from [PKI-ALG]
   --

   -- id-ecPublicKey Parameters are absent, NULL, or ECParameters

   -- Format for both ephemeral and static public keys: Imported from
   -- [PKI-ALG]

   -- ECPoint ::= OCTET STRING

   -- ECParameters ::= CHOICE {
   --   namedCurve      OBJECT IDENTIFIER
   --   commented out in [PKI-ALG]  implicitCurve   NULL
   --   commented out in [PKI-ALG]  specifiedCurve  SpecifiedECDomain
   --   commented out in [PKI-ALG]  ...
   -- }
       -- implicitCurve and specifiedCurve MUST NOT be used in PKIX.
       -- Details for SpecifiedECDomain can be found in [X9.62].
       -- Any future additions to this CHOICE should be coordinated
       -- with ANSI X9.

   -- Format of KeyAgreeRecipientInfo ukm field when used with
   -- ECMQV

   MQVuserKeyingMaterial ::= SEQUENCE {
     ephemeralPublicKey       OriginatorPublicKey,
     addedukm             [0] EXPLICIT UserKeyingMaterial OPTIONAL
   }

   -- 'SharedInfo' for input to KDF when using ECDH and ECMQV with
   -- EnvelopedData, AuthenticatedData, or AuthEnvelopedData

   ECC-CMS-SharedInfo ::= SEQUENCE {
     keyInfo         AlgorithmIdentifier,
     entityUInfo [0] EXPLICIT OCTET STRING OPTIONAL,
     suppPubInfo [2] EXPLICIT OCTET STRING
   }

   --
   -- S/MIME Capabilities
   -- An identifier followed by type.
   --
   --
   -- S/MIME Capabilities: Message Digest Algorithms
   --

   -- Found in [CMS-SHA2].

   --
   -- S/MIME Capabilities: Signature Algorithms
   --

   -- ecdsa-with-SHA1 Type NULL
   -- ecdsa-with-SHA224 Type absent
   -- ecdsa-with-SHA256 Type absent
   -- ecdsa-with-SHA384 Type absent
   -- ecdsa-with-SHA512 Type absent

   --
   -- S/MIME Capabilities: ECDH, Single Pass, Standard
   --

   -- dhSinglePass-stdDH-sha1kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-stdDH-sha224kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-stdDH-sha256kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-stdDH-sha384kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-stdDH-sha512kdf Type is the KeyWrapAlgorithm


   --
   -- S/MIME Capabilities: ECDH, Single Pass, Cofactor
   --

   -- dhSinglePass-cofactorDH-sha1kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-cofactorDH-sha224kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-cofactorDH-sha256kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-cofactorDH-sha384kdf Type is the KeyWrapAlgorithm
   -- dhSinglePass-cofactorDH-sha512kdf Type is the KeyWrapAlgorithm

   --
   -- S/MIME Capabilities: ECMQV, Single Pass, Standard
   --

   -- mqvSinglePass-sha1kdf Type is the KeyWrapAlgorithm
   -- mqvSinglePass-sha224kdf Type is the KeyWrapAlgorithm
   -- mqvSinglePass-sha256kdf Type is the KeyWrapAlgorithm
   -- mqvSinglePass-sha384kdf Type is the KeyWrapAlgorithm
   -- mqvSinglePass-sha512kdf Type is the KeyWrapAlgorithm
   --
   -- S/MIME Capabilities: Message Authentication Code Algorithms
   --

   -- hMACSHA1 Type is preferred absent
   -- id-hmacWithSHA224 Type is absent
   -- if-hmacWithSHA256 Type is absent
   -- id-hmacWithSHA384 Type is absent
   -- id-hmacWithSHA512 Type is absent

   END

A.2. 2004 ASN.1 Module

and now the 2004 version, which is giving a slightly different outfit but the same energy 🦋

CMSECCAlgs-2009-02
  { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
    smime(16) modules(0) id-mod-cms-ecc-alg-2009-02(46) }

DEFINITIONS IMPLICIT TAGS ::=

BEGIN

-- EXPORTS ALL

IMPORTS

-- From [PKI-ASN]

mda-sha1, sa-ecdsaWithSHA1, sa-ecdsaWithSHA224, sa-ecdsaWithSHA256,
sa-ecdsaWithSHA384, sa-ecdsaWithSHA512, id-ecPublicKey,
ECDSA-Sig-Value, ECPoint, ECParameters
  FROM PKIXAlgs-2009
    { iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0)
      id-mod-pkix1-algorithms2008-02(56) }

-- From [PKI-ASN]

mda-sha224, mda-sha256, mda-sha384, mda-sha512
  FROM PKIX1-PSS-OAEP-Algorithms-2009
    { iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0)
      id-mod-pkix1-rsa-pkalgs-02(54) }

-- From [CMS-ASN]

KEY-WRAP, SIGNATURE-ALGORITHM, DIGEST-ALGORITHM, ALGORITHM,
PUBLIC-KEY, MAC-ALGORITHM, CONTENT-ENCRYPTION, KEY-AGREE, SMIME-CAPS,
AlgorithmIdentifier{}
  FROM AlgorithmInformation-2009
    { iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) id-mod(0)
      id-mod-algorithmInformation-02(58) }

-- From [CMS-ASN]

OriginatorPublicKey, UserKeyingMaterial
  FROM CryptographicMessageSyntax-2009
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
      smime(16) modules(0) id-mod-cms-2004-02(41) }

-- From [CMS-ASN]

maca-hMAC-SHA1, cea-3DES-cbc, kwa-3DESWrap, CBCParameter
  FROM CryptographicMessageSyntaxAlgorithms-2009
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
      smime(16) modules(0) id-mod-cmsalg-2001-02(37) }

-- From [CMS-ASN]

cea-aes128-cbc, cea-aes192-cbc, cea-aes256-cbc, kwa-aes128-wrap,
kwa-aes192-wrap, kwa-aes256-wrap
  FROM CMSAesRsaesOaep-2009
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
      smime(16) modules(0) id-mod-cms-aes-02(38) }

-- From [CMS-ASN]

cea-aes128-CCM, cea-aes192-CCM, cea-aes256-CCM, cea-aes128-GCM,
cea-aes192-GCM, cea-aes256-GCM
  FROM CMS-AES-CCM-and-AES-GCM-2009
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
      smime(16) modules(0) id-mod-cms-aes-ccm-gcm-02(44) }

;

-- Constrains the SignedData digestAlgorithms field
-- Constrains the SignedData SignerInfo digestAlgorithm field
-- Constrains the AuthenticatedData digestAlgorithm field

-- Message Digest Algorithms: Imported from [PKI-ASN]

-- MessageDigestAlgs DIGEST-ALGORITHM ::= {
--  mda-sha1   |
--  mda-sha224 |
--  mda-sha256 |
--  mda-sha384 |
--  mda-sha512,
--  ...
-- }

okay bestie, we're still in the digest lineup 💅 and the next bit is the signature algorithms, which is where the signing side gets its options 🦋

-- Constrains the SignedData SignerInfo signatureAlgorithm field

-- Signature Algorithms: Imported from [PKI-ASN]

-- SignatureAlgs SIGNATURE-ALGORITHM ::= {
--  sa-ecdsaWithSHA1   |
--  sa-ecdsaWithSHA224 |
--  sa-ecdsaWithSHA256 |
--  sa-ecdsaWithSHA384 |
--  sa-ecdsaWithSHA512,
--  ...
-- }

-- ECDSA Signature Value: Imported from [PKI-ALG]
-- Contents of SignatureValue OCTET STRING

-- ECDSA-Sig-Value ::= SEQUENCE {
--   r  INTEGER,
--   s  INTEGER
-- }

now the key agreement section, which is giving main character energy 👑 it's the part where two parties agree on a shared key 🫶

--
-- Key Agreement Algorithms
--

-- Constrains the EnvelopedData RecipientInfo KeyAgreeRecipientInfo
--   keyEncryption Algorithm field
-- Constrains the AuthenticatedData RecipientInfo
--   KeyAgreeRecipientInfo keyEncryption Algorithm field
-- Constrains the AuthEnvelopedData RecipientInfo
--   KeyAgreeRecipientInfo keyEncryption Algorithm field

-- DH variants are not used with AuthenticatedData or
-- AuthEnvelopedData

KeyAgreementAlgs KEY-AGREE ::= {
  kaa-dhSinglePass-stdDH-sha1kdf-scheme        |
  kaa-dhSinglePass-stdDH-sha224kdf-scheme      |
  kaa-dhSinglePass-stdDH-sha256kdf-scheme      |
  kaa-dhSinglePass-stdDH-sha384kdf-scheme      |
  kaa-dhSinglePass-stdDH-sha512kdf-scheme      |
  kaa-dhSinglePass-cofactorDH-sha1kdf-scheme   |
  kaa-dhSinglePass-cofactorDH-sha224kdf-scheme |
  kaa-dhSinglePass-cofactorDH-sha256kdf-scheme |
  kaa-dhSinglePass-cofactorDH-sha384kdf-scheme |
  kaa-dhSinglePass-cofactorDH-sha512kdf-scheme |
  kaa-mqvSinglePass-sha1kdf-scheme             |
  kaa-mqvSinglePass-sha224kdf-scheme           |
  kaa-mqvSinglePass-sha256kdf-scheme           |
  kaa-mqvSinglePass-sha384kdf-scheme           |
  kaa-mqvSinglePass-sha512kdf-scheme,
  ...
}
x9-63-scheme OBJECT IDENTIFIER ::= {
  iso(1) identified-organization(3) tc68(133) country(16) x9(840)
  x9-63(63) schemes(0) }

secg-scheme OBJECT IDENTIFIER ::= {
  iso(1) identified-organization(3) certicom(132) schemes(1) }

the DH bits come next, and they're giving standard vibes 🎀

--
-- Diffie-Hellman Single Pass, Standard, with KDFs
--

-- Parameters are always present and indicate the Key Wrap Algorithm

kaa-dhSinglePass-stdDH-sha1kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-stdDH-sha1kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-stdDH-sha1kdf-scheme
}

dhSinglePass-stdDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
  x9-63-scheme 2 }

kaa-dhSinglePass-stdDH-sha224kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-stdDH-sha224kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-stdDH-sha224kdf-scheme
}

dhSinglePass-stdDH-sha224kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 0 }

kaa-dhSinglePass-stdDH-sha256kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-stdDH-sha256kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-stdDH-sha256kdf-scheme
}

dhSinglePass-stdDH-sha256kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 1 }

kaa-dhSinglePass-stdDH-sha384kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-stdDH-sha384kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-stdDH-sha384kdf-scheme
}

dhSinglePass-stdDH-sha384kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 2 }

kaa-dhSinglePass-stdDH-sha512kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-stdDH-sha512kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-stdDH-sha512kdf-scheme
}

dhSinglePass-stdDH-sha512kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 11 3 }

next up is the cofactor flavour of DH, which is basically the same energy with a little extra spice 🌶️

--
-- Diffie-Hellman Single Pass, Cofactor, with KDFs
--

kaa-dhSinglePass-cofactorDH-sha1kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-cofactorDH-sha1kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-cofactorDH-sha1kdf-scheme
}

dhSinglePass-cofactorDH-sha1kdf-scheme OBJECT IDENTIFIER ::= {
  x9-63-scheme 3 }

kaa-dhSinglePass-cofactorDH-sha224kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-cofactorDH-sha224kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-cofactorDH-sha224kdf-scheme
}

dhSinglePass-cofactorDH-sha224kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 0 }

kaa-dhSinglePass-cofactorDH-sha256kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-cofactorDH-sha256kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-cofactorDH-sha256kdf-scheme
}

dhSinglePass-cofactorDH-sha256kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 1 }

kaa-dhSinglePass-cofactorDH-sha384kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-cofactorDH-sha384kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-cofactorDH-sha384kdf-scheme
}

dhSinglePass-cofactorDH-sha384kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 2 }

kaa-dhSinglePass-cofactorDH-sha512kdf-scheme KEY-AGREE ::= {
  IDENTIFIER dhSinglePass-cofactorDH-sha512kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-dhSinglePass-cofactorDH-sha512kdf-scheme
}

dhSinglePass-cofactorDH-sha512kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 14 3 }

and now the MQV ones 💜 same vibe, different math

--
-- MQV Single Pass, Cofactor, with KDFs
--

kaa-mqvSinglePass-sha1kdf-scheme KEY-AGREE ::= {
  IDENTIFIER mqvSinglePass-sha1kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-mqvSinglePass-sha1kdf-scheme
}

mqvSinglePass-sha1kdf-scheme OBJECT IDENTIFIER ::= {
  x9-63-scheme 16 }

kaa-mqvSinglePass-sha224kdf-scheme KEY-AGREE ::= {
  IDENTIFIER mqvSinglePass-sha224kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-mqvSinglePass-sha224kdf-scheme
}

mqvSinglePass-sha224kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 0 }

kaa-mqvSinglePass-sha256kdf-scheme KEY-AGREE ::= {
  IDENTIFIER mqvSinglePass-sha256kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-mqvSinglePass-sha256kdf-scheme
}

mqvSinglePass-sha256kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 1 }

kaa-mqvSinglePass-sha384kdf-scheme KEY-AGREE ::= {
  IDENTIFIER mqvSinglePass-sha384kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-mqvSinglePass-sha384kdf-scheme
}

mqvSinglePass-sha384kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 2 }

kaa-mqvSinglePass-sha512kdf-scheme KEY-AGREE ::= {
  IDENTIFIER mqvSinglePass-sha512kdf-scheme
  PARAMS TYPE KeyWrapAlgorithm ARE required
  UKM -- TYPE unencoded data -- ARE preferredPresent
  SMIME-CAPS cap-kaa-mqvSinglePass-sha512kdf-scheme
}

mqvSinglePass-sha512kdf-scheme OBJECT IDENTIFIER ::= {
  secg-scheme 15 3 }

the key wrap algorithms are up next 🎁 these are imported from [CMS-ASN], so we're just borrowing them

--
-- Key Wrap Algorithms: Imported from [CMS-ASN]
--
KeyWrapAlgorithm ::= AlgorithmIdentifier { KEY-WRAP, { KeyWrapAlgs } }

KeyWrapAlgs KEY-WRAP ::= {
  kwa-3DESWrap    |
  kwa-aes128-wrap |
  kwa-aes192-wrap |
  kwa-aes256-wrap,
  ...
}

--
-- Content Encryption Algorithms: Imported from [CMS-ASN]
--

-- Constrains the EnvelopedData EncryptedContentInfo encryptedContent
-- field and the AuthEnvelopedData EncryptedContentInfo
-- contentEncryptionAlgorithm field

-- ContentEncryptionAlgs CONTENT-ENCRYPTION ::= {
--   cea-3DES-cbc |
--   cea-aes128-cbc   |
--   cea-aes192-cbc   |
--   cea-aes256-cbc   |
--   cea-aes128-ccm   |
--   cea-aes192-ccm   |
--   cea-aes256-ccm   |
--   cea-aes128-gcm   |
--   cea-aes192-gcm   |
--   cea-aes256-gcm,
--   ...
--   }

-- des-ede3-cbc and aes*-cbc are used with EnvelopedData and
-- EncryptedData
-- aes*-ccm are used with AuthEnvelopedData
-- aes*-gcm are used with AuthEnvelopedData
-- (where * is 128, 192, and 256)

now the MAC algorithms, which are the integrity check squad 🛡️

--
-- Message Authentication Code Algorithms
--

-- Constrains the AuthenticatedData
-- MessageAuthenticationCodeAlgorithm field
--
MessageAuthAlgs MAC-ALGORITHM ::= {
--  maca-hMAC-SHA1 |
  maca-hMAC-SHA224 |
  maca-hMAC-SHA256 |
  maca-hMAC-SHA384 |
  maca-hMAC-SHA512,
  ...
}

maca-hMAC-SHA224 MAC-ALGORITHM ::= {
  IDENTIFIER id-hmacWithSHA224
  PARAMS ARE absent
  IS-KEYED-MAC TRUE
  SMIME-CAPS cap-hMAC-SHA224
}

id-hmacWithSHA224 OBJECT IDENTIFIER ::= {
  iso(1) member-body(2) us(840) rsadsi(113549)
  digestAlgorithm(2) 8 }

maca-hMAC-SHA256 MAC-ALGORITHM ::= {
  IDENTIFIER id-hmacWithSHA256
  PARAMS ARE absent
  IS-KEYED-MAC TRUE
  SMIME-CAPS cap-hMAC-SHA256
}

id-hmacWithSHA256 OBJECT IDENTIFIER ::= {
  iso(1) member-body(2) us(840) rsadsi(113549)
  digestAlgorithm(2) 9 }

maca-hMAC-SHA384 MAC-ALGORITHM ::= {
  IDENTIFIER id-hmacWithSHA384
  PARAMS ARE absent
  IS-KEYED-MAC TRUE
  SMIME-CAPS cap-hMAC-SHA384
}

id-hmacWithSHA384 OBJECT IDENTIFIER ::= {
  iso(1) member-body(2) us(840) rsadsi(113549)
  digestAlgorithm(2) 10 }

maca-hMAC-SHA512 MAC-ALGORITHM ::= {
  IDENTIFIER id-hmacWithSHA512
  PARAMS ARE absent
  IS-KEYED-MAC TRUE
  SMIME-CAPS cap-hMAC-SHA512
}
id-hmacWithSHA512 OBJECT IDENTIFIER ::= {
  iso(1) member-body(2) us(840) rsadsi(113549)
  digestAlgorithm(2) 11 }

almost there, and the originator public key stuff is giving "who's the sender" energy 🔑

--
-- Originator Public Key Algorithms
--

-- Constraints on KeyAgreeRecipientInfo OriginatorIdentifierOrKey
-- OriginatorPublicKey algorithm field

OriginatorPKAlgorithms PUBLIC-KEY ::= {
  opka-ec,
  ...
}

opka-ec PUBLIC-KEY ::={
  IDENTIFIER id-ecPublicKey
  KEY ECPoint
  PARAMS TYPE CHOICE { n NULL, p ECParameters } ARE preferredAbsent
}

-- Format for both ephemeral and static public keys: Imported from
-- [PKI-ALG]

-- ECPoint ::= OCTET STRING

-- ECParameters ::= CHOICE {
--   namedCurve      CURVE.&id({NamedCurve})
--   commented out in [PKI-ALG] implicitCurve   NULL
--   commented out in [PKI-ALG] specifiedCurve  SpecifiedECDomain
--   commented out in [PKI-ALG] ...
-- }
  -- implicitCurve and specifiedCurve MUST NOT be used in PKIX.
  -- Details for SpecifiedECDomain can be found in [X9.62].
  -- Any future additions to this CHOICE should be coordinated
  -- with ANSI X.9.

-- Format of KeyAgreeRecipientInfo ukm field when used with
-- ECMQV

MQVuserKeyingMaterial ::= SEQUENCE {
  ephemeralPublicKey       OriginatorPublicKey,
  addedukm             [0] EXPLICIT UserKeyingMaterial OPTIONAL
}
-- 'SharedInfo' for input to KDF when using ECDH and ECMQV with
-- EnvelopedData, AuthenticatedData, or AuthEnvelopedData

ECC-CMS-SharedInfo ::= SEQUENCE {
  keyInfo         KeyWrapAlgorithm,
  entityUInfo [0] EXPLICIT OCTET STRING OPTIONAL,
  suppPubInfo [2] EXPLICIT OCTET STRING
}

--
-- S/MIME CAPS for algorithms in this document
--
SMimeCAPS SMIME-CAPS ::= {
--  mda-sha1.&smimeCaps                                   |
--  mda-sha224.&smimeCaps                                 |
--  mda-sha256.&smimeCaps                                 |
--  mda-sha384.&smimeCaps                                 |
--  mda-sha512.&smimeCaps                                 |
--  sa-ecdsaWithSHA1.&smimeCaps                           |
--  sa-ecdsaWithSHA224.&smimeCaps                         |
--  sa-ecdsaWithSHA256.&smimeCaps                         |
--  sa-ecdsaWithSHA384.&smimeCaps                         |
--  sa-ecdsaWithSHA512.&smimeCaps                         |
  kaa-dhSinglePass-stdDH-sha1kdf-scheme.&smimeCaps        |
  kaa-dhSinglePass-stdDH-sha224kdf-scheme.&smimeCaps      |
  kaa-dhSinglePass-stdDH-sha256kdf-scheme.&smimeCaps      |
  kaa-dhSinglePass-stdDH-sha384kdf-scheme.&smimeCaps      |
  kaa-dhSinglePass-stdDH-sha512kdf-scheme.&smimeCaps      |
  kaa-dhSinglePass-cofactorDH-sha1kdf-scheme.&smimeCaps   |
  kaa-dhSinglePass-cofactorDH-sha224kdf-scheme.&smimeCaps |
  kaa-dhSinglePass-cofactorDH-sha256kdf-scheme.&smimeCaps |
  kaa-dhSinglePass-cofactorDH-sha384kdf-scheme.&smimeCaps |
  kaa-dhSinglePass-cofactorDH-sha512kdf-scheme.&smimeCaps |
  kaa-mqvSinglePass-sha1kdf-scheme.&smimeCaps             |
  kaa-mqvSinglePass-sha224kdf-scheme.&smimeCaps           |
  kaa-mqvSinglePass-sha256kdf-scheme.&smimeCaps           |
  kaa-mqvSinglePass-sha384kdf-scheme.&smimeCaps           |
  kaa-mqvSinglePass-sha512kdf-scheme.&smimeCaps           |
--  kwa-3des.&smimeCaps                                   |
--  kwa-aes128.&smimeCaps                                 |
--  kwa-aes192.&smimeCaps                                 |
--  kwa-aes256.&smimeCaps                                 |
--  cea-3DES-cbc.&smimeCaps                               |
--  cea-aes128-cbc.&smimeCaps                             |
--  cea-aes192-cbc.&smimeCaps                             |
--  cea-aes256-cbc.&smimeCaps                             |
--  cea-aes128-ccm.&smimeCaps                             |
--  cea-aes192-ccm.&smimeCaps                             |
--  cea-aes256-ccm.&smimeCaps                             |
--  cea-aes128-gcm.&smimeCaps                             |
--  cea-aes192-gcm.&smimeCaps                             |
--  cea-aes256-gcm.&smimeCaps                             |
--  maca-hMAC-SHA1.&smimeCaps                             |
  maca-hMAC-SHA224.&smimeCaps                             |
  maca-hMAC-SHA256.&smimeCaps                             |
  maca-hMAC-SHA384.&smimeCaps                             |
  maca-hMAC-SHA512.&smimeCaps,
  ...
}
cap-kaa-dhSinglePass-stdDH-sha1kdf-scheme SMIME-CAPS ::= {
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-stdDH-sha1kdf-scheme
}

cap-kaa-dhSinglePass-stdDH-sha224kdf-scheme SMIME-CAPS ::= {
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-stdDH-sha224kdf-scheme
}

cap-kaa-dhSinglePass-stdDH-sha256kdf-scheme SMIME-CAPS ::= {
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-stdDH-sha256kdf-scheme
}

cap-kaa-dhSinglePass-stdDH-sha384kdf-scheme SMIME-CAPS ::= {
   TYPE KeyWrapAlgorithm
   IDENTIFIED BY dhSinglePass-stdDH-sha384kdf-scheme
}

cap-kaa-dhSinglePass-stdDH-sha512kdf-scheme SMIME-CAPS ::= {
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-stdDH-sha512kdf-scheme
}

cap-kaa-dhSinglePass-cofactorDH-sha1kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-cofactorDH-sha1kdf-scheme
}

cap-kaa-dhSinglePass-cofactorDH-sha224kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-cofactorDH-sha224kdf-scheme
}

cap-kaa-dhSinglePass-cofactorDH-sha256kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-cofactorDH-sha256kdf-scheme
}

cap-kaa-dhSinglePass-cofactorDH-sha384kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-cofactorDH-sha384kdf-scheme
}
cap-kaa-dhSinglePass-cofactorDH-sha512kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY dhSinglePass-cofactorDH-sha512kdf-scheme
}

cap-kaa-mqvSinglePass-sha1kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY mqvSinglePass-sha1kdf-scheme
}

cap-kaa-mqvSinglePass-sha224kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY mqvSinglePass-sha224kdf-scheme
}

cap-kaa-mqvSinglePass-sha256kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY mqvSinglePass-sha256kdf-scheme
}

cap-kaa-mqvSinglePass-sha384kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY mqvSinglePass-sha384kdf-scheme
}

cap-kaa-mqvSinglePass-sha512kdf-scheme SMIME-CAPS ::={
  TYPE KeyWrapAlgorithm
  IDENTIFIED BY mqvSinglePass-sha512kdf-scheme
}

cap-hMAC-SHA224 SMIME-CAPS ::={ IDENTIFIED BY id-hmacWithSHA224 }

cap-hMAC-SHA256 SMIME-CAPS ::={ IDENTIFIED BY id-hmacWithSHA256 }

cap-hMAC-SHA384 SMIME-CAPS ::={ IDENTIFIED BY id-hmacWithSHA384 }

cap-hMAC-SHA512 SMIME-CAPS ::={ IDENTIFIED BY id-hmacWithSHA512 }

END

Appendix B. Changes since RFC 3278 ✨

okay so here's the full glow-up recap of everything that changed since RFC 3278 💅

  • Abstract 🦋: the doc got rebased so it now points at NIST FIPS 186-3 and SP800-56A. BUT for backwards compatibility, the Key Derivation Function from ANSI/SEC1 is still hanging around, no cap.
  • Section 1 🌸: a new bullet got added to cover AuthEnvelopedData.
  • Section 2.1 📝: a sentence got added saying FIPS180-3 is used with ECDSA. The reference to ANSI X9.62 got swapped out for FIPS186-3.
  • Section 2.1.1 🔥: the permitted digest algorithms went from just SHA-1 to SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512. main character energy 👑
  • Section 2.1.2 and 2.1.3 💀: the bullet about integer "e" got deleted. bye bye 👋
  • Section 3 🧚: an explanation got added for why static-static ECDH isn't included. the reasoning is literally the tea ☕
  • Section 3.1 🎀: the DH reference changed from RFC 3852 to RFC 3370. there's also new text saying the fields of EnvelopedData are the same as in CMS.
  • Section 3.1.1 💜: the text now describes all the KeyAgreeRecipientInfo fields. The id-ecPublicKey parameters changed from NULL to absent or ECParameter, and there's extra info about ukm too.
  • Section 3.2 🌈: the sentence about the advantages of 1-Pass ECMQV got rewritten.
  • Section 3.2.1 🍓: the text now describes all the fields. The id-ecPublicKey parameters changed from NULL to absent or ECParameters.
  • Sections 3.2.2 and 4.1.2 🫶: the paragraph about re-using ephemeral keys got reworded.
  • Section 4.1 ⭐: the sentences about the advantages of 1-Pass ECMQV moved over to Section 4.
  • Section 4.1.2 🙈: the note about the attack also moved over to Section 4.
  • Section 4.2 🔥: this whole section is new, and it covers AuthEnvelopedData with ECMQV. iconic 🫶
  • Section 5 👑: this section got moved to Section 8. The first paragraph now recommends both SignedData and EnvelopedData. The requirements got updated for hash algorithms, plus recommendations for matching curves and hash algorithms. The requirements also now spell out which ECDH and ECMQV variants, key wrap algorithms, and content encryption algorithms are required for each content type used in this doc. And the permitted digest algorithms used in KDFs went from SHA-1 to SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512, periodt 💖
  • Section 6 (formerly 7) 🌸: this section got updated so SMIMECapabilities can be present in certificates. S/MIME capabilities for ECDSA with SHA-224, SHA-256, SHA-384, and SHA-512 got added to the list. It also now includes S/MIME capabilities for ECDH and ECMQV using SHA-224, SHA-256, SHA-384, and SHA-512 as the KDF.
  • Section 7.1 (formerly 8.1) 🦋: new sub-sections got added for digest, signature, originator public key, key agreement, content encryption, key wrap, and message authentication code algorithms. It points to the algorithms and parameters in the right documents for SHA-224, SHA-256, SHA-384, and SHA-512, plus SHA-224, SHA-256, SHA-384, and SHA-512 with ECDSA. Algorithm identifiers got added for ECDH std, ECDH cofactor, and ECMQV with SHA-224, SHA-256, SHA-384, and SHA-512 as the KDF. The id-ecPublicKey parameters are now absent, NULL, or ECParameters. If they're present, the originator's ECParameters must match the recipient's ECParameters. 🔥
  • Section 7.2 (formerly 8.2) 💅: this section now includes AuthEnvelopedData. There's also new text about the support requirement for compressed, uncompressed, and hybrid keys. Pointers changed from ANSI X9.61 to PKIX where ECDSA-Sig-Value gets imported, and from SECG to NIST specs. The suppPubInfo example is now AES-256. keyInfo's parameters changed from NULL to any associated parameters, since AES wraps have absent parameters 🧚
  • Section 9 😭: the summary paragraph got swapped out for an updated security considerations section. The paragraph about the definitions of SHA-224, SHA-256, SHA-384, and SHA-512 got deleted.
  • References 📚: all updated.
  • ASN.1 modules 🎀: added.
  • Acknowledgements 💖: updated.

Acknowledgements 🫶

The methods in this doc are based on work done by the ANSI X9F1 working group, so huge thanks to them for helping out. The authors also thanked Peter de Rooij for his patient assistance, and Francois Rousseau's technical comments were super valuable contributions 🌈

Shoutout to the other RFC 3278 authors, Simon Blake-Wilson and Paul Lambert. Honestly, without RFC 3278 this version literally wouldn't exist 💜

The authors also thanked Alfred Hoenes, Jonathan Herzog, Paul Hoffman, Russ Housley, and Jim Schaad for their valuable input ✨

Authors' Addresses 🧚

Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA

EMail: turners@ieca.com


Daniel R. L. Brown
Certicom Corp
5520 Explorer Drive #400
Mississauga, ON L4W 5L1
Canada

EMail: dbrown@certicom.com
📦 where this page comes from