2007-07-31 2012-06-12 IETF consensus 0 Simple S2K 1 Salted S2K 2 Reserved value 3 Iterated and Salted S2K 4-99 Unassigned 100-110 Private/Experimental S2K 111-255 Unassigned IETF consensus 0 Reserved - a packet tag MUST NOT have this value 1 Public-Key Encrypted Session Key Packet 2 Signature Packet 3 Symmetric-Key Encrypted Session Key Packet 4 One-Pass Signature Packet 5 Secret Key Packet 6 Public Key Packet 7 Secret Subkey Packet 8 Compressed Data Packet 9 Symmetrically Encrypted Data Packet 10 Marker Packet 11 Literal Data Packet 12 Trust Packet 13 User ID Packet 14 Public Subkey Packet 15-16 Unknown 17 User Attribute Packet 18 Sym. Encrypted and Integrity Protected Data Packet 19 Modification Detection Code Packet 20-59 Unassigned 60-63 Private or Experimental Values IETF consensus 0 Reserved 1 image 2-99 Unassigned 100-110 Experimental or private use 111-255 Unassigned IETF consensus 0 Reserved 1 JPEG 2-99 Unassigned 100-110 Experimental or private use 111-255 Unassigned IETF consensus 0 Reserved 1 Reserved 2 signature creation time 3 signature expiration time 4 exportable certification 5 trust signature 6 regular expression 7 revocable 8 Reserved 9 key expiration time 10 placeholder for backward compatibility 11 preferred symmetric algorithms 12 revocation key 13-15 Reserved 16 issuer key ID 17-19 Reserved 20 notation data 21 preferred hash algorithms 22 preferred compression algorithms 23 key server preferences 24 preferred key server 25 primary User ID 26 policy URI 27 key flags 28 signer's User ID 29 reason for revocation 30 features 31 signature target 32 embedded signature 33-99 Unassigned 100-110 Private or experimental 111-127 Unassigned Expert Review Notation names are arbitrary strings encoded in UTF-8. They reside two name spaces: The IETF name space and the user name space. The IETF name space is registered with IANA. These names MUST NOT contain the "@" character (0x40). This is a tag for the user name space. IETF Consensus This is a variable length bit field. 0x00-0x07 Unassigned 0x80 No-modify IETF Consensus 0 No reason specified (key revocations or cert revocations) 1 Key is superseded (key revocations) 2 Key material has been compromised (key revocations) 3 Key is retired and no longer used (key revocations) 4-31 Unassigned 32 User ID information is no longer valid (cert revocations) 33-99 Unassigned 100-110 Private Use 111-255 Unassigned IETF Consensus 0x01 Modification Detection (packets 18 and 19) 0x02-0x80 Unassigned IETF Consensus IETF Consensus The flags in this packet may appear in self-signatures or in certification signatures. They mean different things depending on who is making the statement -- for example, a certification signature that has the "sign data" flag is stating that the certification is for that use. On the other hand, the "communications encryption" flag in a self-signature is stating a preference that a given key be used for communications. Note however, that it is a thorny issue to determine what is "communications" and what is "storage." This decision is left wholly up to the implementation; the authors of this document do not claim any special wisdom on the issue, and realize that accepted opinion may change. The "split key" (0x10) and "group key" (0x80) flags are placed on a self-signature only; they are meaningless on a certification signature. They SHOULD be placed only on a direct-key signature (type 0x1f) or a subkey signature (type 0x18), one that refers to the key the flag applies to. 0x01 This key may be used to certify other keys. 0x02 This key may be used to sign data. 0x04 This key may be used to encrypt communications. 0x08 This key may be used to encrypt storage. 0x10 The private component of this key may have been split by a secret-sharing mechanism. 0x20 This key may be used for authentication. 0x80 The private component of this key may be in the possession of more than one person. IETF Consensus 0 Reserved 1 RSA (Encrypt or Sign) Alfred Menezes, Paul van Oorschot, and Scott Vanstone, "Handbook of Applied Cryptography," CRC Press, 1996. 2 RSA Encrypt-Only 3 RSA Sign-Only 4-15 Unassigned 16 Elgamal (Encrypt-Only) T. Elgamal, "A Public-Key Cryptosystem and a Signature Scheme Based on Discrete Logarithms," IEEE Transactions on Information Theory, v. IT-31, n. 4, 1985, pp. 469-472. Alfred Menezes, Paul van Oorschot, and Scott Vanstone, "Handbook of Applied Cryptography," CRC Press, 1996. 17 DSA (Digital Signature Algorithm) Digital Signature Standard (DSS) (FIPS PUB 186-2). FIPS 186-3 describes keys greater than 1024 bits. Alfred Menezes, Paul van Oorschot, and Scott Vanstone, "Handbook of Applied Cryptography," CRC Press, 1996. 18 ECDH public key algorithm 19 ECDSA public key algorithm 20 Reserved (formerly Elgamal Encrypt or Sign) 21 Reserved for Diffie-Hellman (X9.42, as defined for IETF-S/MIME) 22-99 Unassigned 100-110 Private/Experimental algorithm 111-255 Unassigned IETF Consensus 0 Plaintext or unencrypted data 1 IDEA Lai, X., "On the design and security of block ciphers", ETH Series in Information Processing, J.L. Massey (editor), Vol. 1, Hartung-Gorre Verlag Knostanz, Technische Hochschule (Zurich), 1992 2 TripleDES (DES-EDE, [SCHNEIER] [HAC] 168 bit key derived from 192) 3 CAST5 (128 bit key, as per RFC 2144) 4 Blowfish (128 bit key, 16 rounds) Schneier, B. "Description of a New Variable-Length Key, 64-Bit Block Cipher (Blowfish)" Fast Software Encryption, Cambridge Security Workshop Proceedings (December 1993), Springer-Verlag, 1994, pp191-204 5 Reserved 6 Reserved 7 AES with 128-bit key Advanced Encryption Standards Questions and Answers 8 AES with 192-bit key Advanced Encryption Standards Questions and Answers 9 AES with 256-bit key Advanced Encryption Standards Questions and Answers 10 Twofish with 256-bit key B. Schneier, J. Kelsey, D. Whiting, D. Wagner, C. Hall, and N. Ferguson, "The Twofish Encryption Algorithm", John Wiley & Sons, 1999. 11 Camellia with 128 bit key 12 Camellia with 192 bit key 13 Camellia with 256 bit key 14-99 Unassigned 100-110 Private/Experimental algorithm 111-255 Unassigned IETF Consensus 1 MD5 (deprecated) "MD5" Alfred Menezes, Paul van Oorschot, and Scott Vanstone, "Handbook of Applied Cryptography," CRC Press, 1996. 2 SHA-1 "SHA1" [FIPS180] 3 RIPE-MD/160 "RIPEMD160" Alfred Menezes, Paul van Oorschot, and Scott Vanstone, "Handbook of Applied Cryptography," CRC Press, 1996. 4-7 Reserved 8 SHA256 "SHA256" [FIPS180] 9 SHA384 "SHA384" [FIPS180] 10 SHA512 "SHA512" [FIPS180] 11 SHA224 "SHA224" [FIPS180] 12-99 Unassigned 100-110 Private/Experimental algorithm 111-255 Unassigned IETF Consensus 0 Uncompressed 1 ZIP 2 ZLIB 3 BZip2 J. Seward, jseward&acm.org, "The Bzip2 and libbzip2 home page" 4-99 Unassigned 100-110 Private/Experimental algorithm 111-255 Unassigned