RFC 3602

The AES-CBC Cipher Algorithm and Its Use with IPsec

📅 published September 2003, from ietf

RFC 3602: The AES-CBC Cipher Algorithm and Its Use with IPsec ✨🎀

Bestie, this one is a big deal 💖 It's an Internet standards track doc (category: Standards Track 🦋), dated September 2003. It was written by S. Frankel and R. Glenn from NIST, plus S. Kelly from Airespace 🌸. It doesn't obsolete or update any other RFCs, since the original doesn't list any.

Status of This Memo 📜

This document specifies an Internet standards track protocol for the Internet community, and asks for discussion and suggestions for improvements 💬. For the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1) 🔍. Distribution of this memo is unlimited 🌈.

Copyright Notice ©️

Abstract ✨

So this doc describes how to use the Advanced Encryption Standard (AES) cipher in Cipher Block Chaining (CBC) mode, with an explicit Initialization Vector (IV). The whole point is to give you confidentiality inside the IPsec Encapsulating Security Payload (ESP) 🔐💅.

Table of Contents 🗂️

1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.1.  Specification of Requirements. . . . . . . . . . . . . .  3
2.  The AES Cipher Algorithm . . . . . . . . . . . . . . . . . . .  3
    2.1.  Mode . . . . . . . . . . . . . . . . . . . . . . . . . .  3
    2.2.  Key Size and Number of Rounds. . . . . . . . . . . . . .  4
    2.3.  Weak Keys. . . . . . . . . . . . . . . . . . . . . . . .  4
    2.4.  Block Size and Padding . . . . . . . . . . . . . . . . .  4
    2.5.  Additional Information . . . . . . . . . . . . . . . . .  4
    2.6.  Performance. . . . . . . . . . . . . . . . . . . . . . .  5
3.  ESP Payload  . . . . . . . . . . . . . . . . . . . . . . . . .  5
    3.1.  ESP Algorithmic Interactions . . . . . . . . . . . . . .  6
    3.2.  Keying Material. . . . . . . . . . . . . . . . . . . . .  6
4.  Test Vectors . . . . . . . . . . . . . . . . . . . . . . . . .  6
5.  IKE Interactions . . . . . . . . . . . . . . . . . . . . . . . 10
    5.1.  Phase 1 Identifier . . . . . . . . . . . . . . . . . . . 10
    5.2.  Phase 2 Identifier . . . . . . . . . . . . . . . . . . . 10
    5.3.  Key Length Attribute . . . . . . . . . . . . . . . . . . 10
    5.4.  Hash Algorithm Considerations. . . . . . . . . . . . . . 10
6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
8.  Intellectual Property Rights Statement . . . . . . . . . . . . 11
9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
    9.1.  Normative References . . . . . . . . . . . . . . . . . . 12
    9.2.  Informative References . . . . . . . . . . . . . . . . . 12
10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
11. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14
12. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 15

1. Introduction 🌟

Okay so, after a four-year competitive process, NIST (the National Institute of Standards and Technology) picked the AES (Advanced Encryption Standard) 👑. It's the successor to the venerable DES (Data Encryption Standard) 🧓. The competition was open, with public participation and comments invited at every step 🗣️. The AES [AES], formerly known as Rijndael, won out over a field of five finalists 🏆.

The AES was chosen based on several characteristics 💅:

security
unclassified
publicly disclosed
available royalty-free, worldwide
capable of handling a block size of at least 128 bits
at a minimum, capable of handling key sizes of 128, 192, and 256 bits
computational efficiency and memory requirements on a variety of software and hardware, including smart cards
flexibility, simplicity and ease of implementation

The AES will be the government's designated encryption cipher 🇺🇸. The expectation is that it will keep sensitive (unclassified) government information safe until at least the next century ⏳. It's also expected to be widely adopted by businesses and financial institutions 🏦.

Here's the big plan: it is the intention of the IETF IPsec Working Group that AES will eventually be adopted as the default IPsec ESP cipher and will obtain the status of MUST be included in compliant IPsec implementations 🔥.

The rest of this document explains how to use AES inside IPsec ESP 🎀. If you want to know how all the ESP pieces fit together to provide security services, check out [ARCH], [ESP], and [ROAD] 📚.

1.1. Specification of Requirements 📝

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" that appear in this document are to be interpreted as described in [RFC-2119] 🧚.

2. The AES Cipher Algorithm 🔐

All symmetric block ciphers share some common stuff: mode, key size, weak keys, block size, and rounds 🎀. The sections below describe the relevant characteristics of the AES cipher 🦋.

2.1. Mode 🌸

NIST has defined 5 modes of operation for AES and other FIPS-approved ciphers [MODES] 🌈: CBC (Cipher Block Chaining), ECB (Electronic CodeBook), CFB (Cipher FeedBack), OFB (Output FeedBack) and CTR (Counter). CBC mode is well-defined and well-understood for symmetric ciphers, and it's currently required for all other ESP ciphers 💖. This document specifies AES in CBC mode within ESP 🫶. This mode needs an Initialization Vector (IV) that is the same size as the block size 📏. Using a randomly generated IV stops identical ciphertext from showing up when packets have identical data across the first block of the cipher's block size 🙈.

The IV gets XOR'd with the first plaintext block before it's encrypted ✨. After that, for each successive block, the previous ciphertext block gets XOR'd with the current plaintext, and only then is it encrypted 🔁.

More info on CBC mode can be found in [MODES, CRYPTO-S] 📖. For using CBC mode in ESP with 64-bit ciphers, see [CBC] 💜.

2.2. Key Size and Number of Rounds 🔑

AES supports three key sizes: 128 bits, 192 bits, and 256 bits 🌟. The default key size is 128 bits, and all implementations MUST support this key size 💅. Implementations MAY also support key sizes of 192 bits and 256 bits 🦄.

AES uses a different number of rounds for each key size 🔄. When a 128-bit key is used, implementations MUST use 10 rounds. When a 192-bit key is used, implementations MUST use 12 rounds. When a 256-bit key is used, implementations MUST use 14 rounds 🎯.

2.3. Weak Keys 🥀

At the time of writing this document, there are no known weak keys for the AES 🙌.

Some cipher algorithms have weak keys, or keys that MUST not be used, because of how they interact with some part of the cipher's definition 😬. If weak keys are ever discovered for AES, then weak keys SHOULD be checked for and discarded when using manual key management 🕵️. When using dynamic key management, such as [IKE], weak key checks SHOULD NOT be performed, because they're seen as unnecessary extra code complexity that could weaken the intended security [EVALUATION] 🙅‍♀️.

2.4. Block Size and Padding 🧩

AES uses a block size of sixteen octets (128 bits) 🍓.

Padding is required by AES to keep a 16-octet (128-bit) blocksize 📐. Padding MUST be added, as specified in [ESP], so that the data to be encrypted (which includes the ESP Pad Length and Next Header fields) has a length that's a multiple of 16 octets 💫.

Because of this algorithm-specific padding requirement, you don't need any extra padding to make sure the ciphertext ends on a 4-octet boundary 🙃. Keeping a 16-octet blocksize already guarantees that the ESP Pad Length and Next Header fields will be right aligned within a 4-octet word ✅. Additional padding MAY be included, as specified in [ESP], as long as the 16-octet blocksize is maintained 🌷.

2.5. Additional Information 📚

AES was invented by Joan Daemen from Banksys/PWI and Vincent Rijmen from ESAT-COSIC, both in Belgium 🇧🇪. It's available worldwide on a royalty-free basis 🌍. It isn't covered by any patents, and the Rijndael homepage says: "Rijndael is available for free. You can use it for whatever purposes you want, irrespective of whether it is accepted as AES or not." 💅 The AES description can be found in [AES] 📖. The Rijndael homepage is http://www.esat.kuleuven.ac.be/~rijmen/rijndael/ 🔗.

The AES homepage, http://www.nist.gov/aes, is packed with info about AES 🤩. That includes a definitive description of the algorithm, performance stats, test vectors, and intellectual property info 💜. It also explains how to get an AES reference implementation from NIST 🧑‍💻.

2.6. Performance 🏎️

If you want a comparison table of the estimated speeds of AES and other cipher algorithms, check out [PERF-1], [PERF-2], [PERF-3], or [PERF-4] 📊. The AES homepage has pointers to other analyses too 🫶.

3. ESP Payload 📦

The ESP payload is the IV followed by raw ciphertext 🎁. So the payload field, as defined in [ESP], breaks down according to this diagram 👀:

   +---------------+---------------+---------------+---------------+
   |                                                               |
   +               Initialization Vector (16 octets)               +
   |                                                               |
   +---------------+---------------+---------------+---------------+
   |                                                               |
   ~ Encrypted Payload (variable length, a multiple of 16 octets)  ~
   |                                                               |
   +---------------------------------------------------------------+

The IV field MUST be the same size as the block size of the cipher algorithm being used 📏. The IV MUST be chosen at random, and MUST be unpredictable 🎲.

Including the IV in each datagram means you can decrypt every received datagram, even when some datagrams get dropped or arrive out of order 🚚.

To avoid CBC encrypting very similar plaintext blocks in different packets, implementations MUST NOT use a counter or other low-Hamming distance source for IVs 🙅‍♀️. Bestie, that's a big no-no 💀.

3.1. ESP Algorithmic Interactions 🤝

Right now, there are no known issues with how AES interacts with other parts of ESP, like certain authentication schemes ✅.

3.2. Keying Material 🗝️

The minimum number of bits sent from the key exchange protocol to the ESP algorithm must be greater than or equal to the key size 💫.

The cipher's encryption and decryption key is taken from the first <x> bits of the keying material, where <x> represents the required key size 🌈.

(Part 1 of 3, more to come! 🧚💖)

4. Test Vectors ✨

okay so this section is the best part bc it's all the receipts 🧾💅. The first 4 test cases check AES-CBC encryption. Each one gives you the key, the plaintext, and the ciphertext you should get back. Keys and data are either hex numbers (starting with "0x") or ASCII strings in double quotes. If it's an ASCII string, the AES-CBC math for that case does not include the trailing null character ('\0') at the end of the string 🙈. The computed ciphertext values are always hex numbers.

The last 4 test cases show sample ESP packets that use AES-CBC for encryption 🎀. All the data there is hex, and none of it starts with "0x".

These vectors were checked against 2 separate implementations: the NIST AES-CBC reference implementation, and one from the people who wrote the Rijndael algorithm (http://csrc.nist.gov/encryption/aes/rijndael/rijndael-unix-refc.tar). Two independent checkers agreeing is so iconic 👑.

Case #1: AES-CBC, 1 block, 128-bit key

Case #1: Encrypting 16 bytes (1 block) using AES-CBC with 128-bit key
Key       : 0x06a9214036b8a15b512e03d534120006
IV        : 0x3dafba429d9eb430b422da802c9fac41
Plaintext : "Single block msg"
Ciphertext: 0xe353779c1079aeb82708942dbe77181a

Case #2: AES-CBC, 2 blocks, 128-bit key

Case #2: Encrypting 32 bytes (2 blocks) using AES-CBC with 128-bit key
Key       : 0xc286696d887c9aa0611bbb3e2025a45a
IV        : 0x562e17996d093d28ddb3ba695a2e6f58
Plaintext : 0x000102030405060708090a0b0c0d0e0f
              101112131415161718191a1b1c1d1e1f
Ciphertext: 0xd296cd94c2cccf8a3a863028b5e1dc0a
              7586602d253cfff91b8266bea6d61ab1

Case #3: AES-CBC, 3 blocks, 128-bit key

Case #3: Encrypting 48 bytes (3 blocks) using AES-CBC with 128-bit key
Key       : 0x6c3ea0477630ce21a2ce334aa746c2cd
IV        : 0xc782dc4c098c66cbd9cd27d825682c81
Plaintext : "This is a 48-byte message (exactly 3 AES blocks)"
Ciphertext: 0xd0a02b3836451753d493665d33f0e886
              2dea54cdb293abc7506939276772f8d5
              021c19216bad525c8579695d83ba2684

Case #4: AES-CBC, 4 blocks, 128-bit key

Case #4: Encrypting 64 bytes (4 blocks) using AES-CBC with 128-bit key
Key       : 0x56e47a38c5598974bc46903dba290349
IV        : 0x8ce82eefbea0da3c44699ed7db51b7d9
Plaintext : 0xa0a1a2a3a4a5a6a7a8a9aaabacadaeaf
              b0b1b2b3b4b5b6b7b8b9babbbcbdbebf
              c0c1c2c3c4c5c6c7c8c9cacbcccdcecf
              d0d1d2d3d4d5d6d7d8d9dadbdcdddedf
Ciphertext: 0xc30e32ffedc0774e6aff6af0869f71aa
              0f3af07a9a31a9c684db207eb0ef8e4e
              35907aa632c3ffdf868bb7b29d3d46ad
              83ce9f9a102ee99d49a53e87f4c3da55

Case #5: sample transport-mode ESP packet (ping 192.168.123.100) 🦋

This one walks through the whole packet glow-up, step by step. First the original packet, then the padding and trailer get tacked on, and then you get the encrypted version with the SPI, sequence number, and IV.

Case #5: Sample transport-mode ESP packet (ping 192.168.123.100)
Key: 90d382b4 10eeba7a d938c46c ec1a82bf
SPI: 4321
Source address: 192.168.123.3
Destination address: 192.168.123.100
Sequence number: 1
IV: e96e8c08 ab465763 fd098d45 dd3ff893

Original packet:
IP header (20 bytes): 45000054 08f20000 4001f9fe c0a87b03 c0a87b64
Data (64 bytes):
08000ebd a70a0000 8e9c083d b95b0700 08090a0b 0c0d0e0f 10111213 14151617
18191a1b 1c1d1e1f 20212223 24252627 28292a2b 2c2d2e2f 30313233 34353637

Augment data with:
Padding: 01020304 05060708 090a0b0c 0d0e
Pad length: 0e
Next header: 01 (ICMP)

Pre-encryption Data with padding, pad length and next header (80 bytes):
08000ebd a70a0000 8e9c083d b95b0700 08090a0b 0c0d0e0f 10111213 14151617
18191a1b 1c1d1e1f 20212223 24252627 28292a2b 2c2d2e2f 30313233 34353637
01020304 05060708 090a0b0c 0d0e0e01
Post-encryption packet with SPI, Sequence number, IV:
IP header: 4500007c 08f20000 4032f9a5 c0a87b03 c0a87b64
SPI/Seq #: 00004321 00000001
IV: e96e8c08 ab465763 fd098d45 dd3ff893
Encrypted Data (80 bytes):
f663c25d 325c18c6 a9453e19 4e120849 a4870b66 cc6b9965 330013b4 898dc856
a4699e52 3a55db08 0b59ec3a 8e4b7e52 775b07d1 db34ed9c 538ab50c 551b874a
a269add0 47ad2d59 13ac19b7 cfbad4a6

Case #6: sample transport-mode ESP packet (ping -p 77 -s 20 192.168.123.100) 🍓

Case #6: Sample transport-mode ESP packet
         (ping -p 77 -s 20 192.168.123.100)
Key: 90d382b4 10eeba7a d938c46c ec1a82bf
SPI: 4321
Source address: 192.168.123.3
Destination address: 192.168.123.100
Sequence number: 8
IV: 69d08df7 d203329d b093fc49 24e5bd80

Original packet:
IP header (20 bytes): 45000030 08fe0000 4001fa16 c0a87b03 c0a87b64
Data (28 bytes):
0800b5e8 a80a0500 a69c083d 0b660e00 77777777 77777777 77777777

Augment data with:
Padding: 0102
Pad length: 02
Next header: 01 (ICMP)

Pre-encryption Data with padding, pad length and next header (32 bytes):
0800b5e8 a80a0500 a69c083d 0b660e00 77777777 77777777 77777777 01020201

Post-encryption packet with SPI, Sequence number, IV:
IP header: 4500004c 08fe0000 4032f9c9 c0a87b03 c0a87b64
SPI/Seq #: 00004321 00000008
IV: 69d08df7 d203329d b093fc49 24e5bd80
Encrypted Data (32 bytes):
f5199588 1ec4e0c4 488987ce 742e8109 689bb379 d2d750c0 d915dca3 46a89f75

Case #7: sample tunnel-mode ESP packet (ping 192.168.123.200) 🧚

This one is tunnel mode, so the whole original IP header gets wrapped up inside the encrypted payload. Next header is 04 (IP-in-IP) here 💜.

Case #7: Sample tunnel-mode ESP packet (ping 192.168.123.200)
Key: 01234567 89abcdef 01234567 89abcdef
SPI: 8765
Source address: 192.168.123.3
Destination address: 192.168.123.200
Sequence number: 2
IV: f4e76524 4f6407ad f13dc138 0f673f37
Original packet:
IP header (20 bytes): 45000054 09040000 4001f988 c0a87b03 c0a87bc8
Data (64 bytes):
08009f76 a90a0100 b49c083d 02a20400 08090a0b 0c0d0e0f 10111213 14151617
18191a1b 1c1d1e1f 20212223 24252627 28292a2b 2c2d2e2f 30313233 34353637

Augment data with:
Padding: 01020304 05060708 090a
Pad length: 0a
Next header: 04 (IP-in-IP)

Pre-encryption Data with original IP header, padding, pad length and
                         next header (96 bytes):
45000054 09040000 4001f988 c0a87b03 c0a87bc8 08009f76 a90a0100 b49c083d
02a20400 08090a0b 0c0d0e0f 10111213 14151617 18191a1b 1c1d1e1f 20212223
24252627 28292a2b 2c2d2e2f 30313233 34353637 01020304 05060708 090a0a04

Post-encryption packet with SPI, Sequence number, IV:
IP header: 4500008c 09050000 4032f91e c0a87b03 c0a87bc8
SPI/Seq #: 00008765 00000002
IV: f4e76524 4f6407ad f13dc138 0f673f37
Encrypted Data (96 bytes):
773b5241 a4c44922 5e4f3ce5 ed611b0c 237ca96c f74a9301 3c1b0ea1 a0cf70f8
e4ecaec7 8ac53aad 7a0f022b 859243c6 47752e94 a859352b 8a4d4d2d ecd136e5
c177f132 ad3fbfb2 201ac990 4c74ee0a 109e0ca1 e4dfe9d5 a100b842 f1c22f0d

Case #8: sample tunnel-mode ESP packet (ping -p ff -s 40 192.168.123.200) 🌈

Case #8: Sample tunnel-mode ESP packet
         (ping -p ff -s 40 192.168.123.200)
Key: 01234567 89abcdef 01234567 89abcdef
SPI: 8765
Source address: 192.168.123.3
Destination address: 192.168.123.200
Sequence number: 5
IV: 85d47224 b5f3dd5d 2101d4ea 8dffab22

Original packet:
IP header (20 bytes): 45000044 090c0000 4001f990 c0a87b03 c0a87bc8
Data (48 bytes):
0800d63c aa0a0200 c69c083d a3de0300 ffffffff ffffffff ffffffff ffffffff
ffffffff ffffffff ffffffff ffffffff

Augment data with:
Padding: 01020304 05060708 090a
Pad length: 0a
Next header: 04 (IP-in-IP)
Pre-encryption Data with original IP header, padding, pad length and
                         next header (80 bytes):
45000044 090c0000 4001f990 c0a87b03 c0a87bc8 0800d63c aa0a0200 c69c083d
a3de0300 ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff
ffffffff 01020304 05060708 090a0a04

Post-encryption packet with SPI, Sequence number, IV:
IP header: 4500007c 090d0000 4032f926 c0a87b03 c0a87bc8
SPI/Seq #: 00008765 00000005
IV: 85d47224 b5f3dd5d 2101d4ea 8dffab22
Encrypted Data (80 bytes):
15b92683 819596a8 047232cc 00f7048f e45318e1 1f8a0f62 ede3c3fc 61203bb5
0f980a08 c9843fd3 a1b06d5c 07ff9639 b7eb7dfb 3512e5de 435e7207 ed971ef3
d2726d9b 5ef6affc 6d17a0de cbb13892

5. IKE Interactions 🫶

5.1. Phase 1 Identifier

okay so for Phase 1 negotiations, IANA gave AES-CBC an Encryption Algorithm ID of 7 🌸.

5.2. Phase 2 Identifier

and for Phase 2 negotiations, IANA gave ESP_AES an ESP Transform Identifier of 12 ✨.

5.3. Key Length Attribute

bestie, AES comes in variable key lengths, so the Key Length attribute MUST be specified in both a Phase 1 exchange [IKE] and a Phase 2 exchange [DOI]. no skipping it!! 🔥

5.4. Hash Algorithm Considerations

there was a whole companion competition to pick the successor to SHA-1, the widely-used hash algorithm, and it just wrapped up 🏆. The winners are SHA-256, SHA-384 and SHA-512 [SHA2-1, SHA2-2]. They can make outputs of three different lengths (256, 384 and 512 bits), which is plenty to generate keys (within IKE) and authenticate (within ESP) all three AES key sizes (128, 192 and 256 bits). iconic 💅.

But HMAC-SHA-1 [HMAC-SHA] and HMAC-MD5 [HMAC-MD5] are currently considered strong enough to do both jobs for 128-bit AES keys: generating them as IKE generators, and authenticating ESP for AES encryption with 128-bit keys 🦋.

6. Security Considerations 💀

ngl this part is serious, so read it carefully 🙈. Implementations are encouraged to use the largest key sizes they can, once they've thought about performance on their particular hardware and software setup. Encryption hits both sides of a secure channel, so that performance check has to cover the server as well as the client, not just the client side 👑. That said, a 128-bit key is considered secure for the foreseeable future.

For more about why you need random IV values, check out [CRYPTO-B].

For further security considerations, the reader is encouraged to read [AES] 📚.

7. IANA Considerations 🌸

IANA has assigned Encryption Algorithm ID 7 to AES-CBC, and ESP Transform Identifier 12 to ESP_AES. Those numbers are officially theirs now 💖.

8. Intellectual Property Rights Statement ⚖️

The IETF takes no position on whether any intellectual property or other rights claimed to cover the technology in this document are valid or in scope, or on whether any license under those rights might or might not be available. It also doesn't say it has tried to find any such rights. Info about the IETF's procedures for rights in standards-track and standards-related documents can be found in BCP-11. Copies of claims of rights that have been made available for publication, any assurances of licenses that will be made available, or the result of an attempt to get a general license or permission for implementers or users to use those proprietary rights can be obtained from the IETF Secretariat.

The IETF invites anyone interested to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology required to practice this standard. Please send that info to the IETF Executive Director.

9. References 📖

9.1. Normative References

[AES]: NIST, FIPS PUB 197, "Advanced Encryption Standard (AES)," November 2001. http://csrc.nist.gov/publications/fips/fips197/fips-197.{ps,pdf}
[CBC]: Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher Algorithms", RFC 2451, November 1998.
[ESP]: Kent, S. and R. Atkinson, "IP Encapsulating Security Payload (ESP)", RFC 2406, November 1998.

9.2. Informative References 📚

okay bestie, these are the extra-credit reads 🤓💅 Here's the whole reading list, citations exact:

[ARCH] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. 🏛️

[CRYPTO-B] Bellovin, S., "Probable Plaintext Cryptanalysis of the IP Security Protocols", Proceedings of the Symposium on Network and Distributed System Security, San Diego, CA, pp. 155-160, February 1997. http://www.research.att.com/~smb/papers/probtxt.pdf 🔐

[CRYPTO-S] B. Schneier, "Applied Cryptography Second Edition", John Wiley & Sons, New York, NY, 1995, ISBN 0-471-12845-7. 📖

[DOI] Piper, D., "The Internet IP Security Domain of Interpretation for ISAKMP", RFC 2407, November 1998. 🗂️

[EVALUATION] Ferguson, N. and B. Schneier, "A Cryptographic Evaluation of IPsec," Counterpane Internet Security, Inc., January 2000. http://www.counterpane.com/ipsec.pdf 🔍

[HMAC-MD5] Madson, C. and R. Glenn, "The Use of HMAC-MD5-96 within ESP and AH", RFC 2403, November 1998. 🧩

[HMAC-SHA] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within ESP and AH", RFC 2404, November 1998. 🧩

[IKE] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, November 1998. 🗝️

[MODES] Dworkin, M., "Recommendation for Block Cipher Modes of Operation: Methods and Techniques," NIST Special Publication 800-38A, December 2001. http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf 🧱

[PERF-1] Bassham, L. III, "Efficiency Testing of ANSI C Implementations of Round1 Candidate Algorithms for the Advanced Encryption Standard." http://csrc.nist.gov/encryption/aes/round1/r1-ansic.pdf ⏱️

[PERF-2] Lipmaa, Helger, "AES/Rijndael: speed." http://www.tcs.hut.fi/~helger/aes/rijndael.html 🏎️

[PERF-3] Nechvetal, J., E. Barker, D. Dodson, M. Dworkin, J. Foti and E. Roback, "Status Report on the First Round of the Development of the Advanced Encryption Standard." http://csrc.nist.gov/encryption/aes/round1/r1report.pdf 📊

[PERF-4] Schneier, B., J. Kelsey, D. Whiting, D. Wagner, C. Hall, and N. Ferguson, "Performance Comparison of the AES Submissions." http://www.counterpane.com/aes-performance.pdf 🥇

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

[ROAD] Thayer, R., Doraswamy, N. and R. Glenn, "IP Security Document Roadmap", RFC 2411, November 1998. 🗺️

[SHA2-1] NIST, FIPS PUB 180-2 "Specifications for the Secure Hash Standard," August 2002. http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf 🔗

[SHA2-2] "Descriptions of SHA-256, SHA-384, and SHA-512." http://csrc.nist.gov/cryptval/shs/sha256-384-512.pdf 🧾

10. Acknowledgments 🫶

Okay so this part is giving gratitude 💖 Portions of this text, plus its general structure, were unabashedly lifted from [CBC]. No shame, just vibes 🙈

The authors want to thank Hilarie Orman for providing expert advice (and a sanity check) on key sizes, requirements for Diffie-Hellman groups, and IKE interactions. 🧠✨ We also thank Scott Fluhrer for his helpful comments and recommendations. 🌸

11. Authors' Addresses 📮

The authors, with their contact deets:

Sheila Frankel
NIST
820 West Diamond Ave.
Room 677
Gaithersburg, MD 20899

Phone: +1 (301) 975-3297
EMail: sheila.frankel@nist.gov

Scott Kelly
Airespace
110 Nortech Pkwy
San Jose CA 95134

Phone: +1 408 635 2000
EMail: scott@hyperthought.com

Rob Glenn
NIST
820 West Diamond Ave.
Room 605
Gaithersburg, MD 20899

Phone: +1 (301) 975-3667
EMail: rob.glenn@nist.gov

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Acknowledgement 🌈

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📦 where this page comes from

ietf: rfc3602 2003-09
💖 girlified by claude-haiku-5-5 on 2026-10-16: a language model's rewrite of the original, under its terms