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Appendix C. Cipher Suite Definitions

This appendix defines cipher suites that are new or updated in TLS 1.2.

C.1. AES Cipher Suites​

The following cipher suites use the AES algorithm:

CipherSuite TLS_RSA_WITH_AES_128_CBC_SHA      = { 0x00,0x2F };
CipherSuite TLS_DH_DSS_WITH_AES_128_CBC_SHA   = { 0x00,0x30 };
CipherSuite TLS_DH_RSA_WITH_AES_128_CBC_SHA   = { 0x00,0x31 };
CipherSuite TLS_DHE_DSS_WITH_AES_128_CBC_SHA  = { 0x00,0x32 };
CipherSuite TLS_DHE_RSA_WITH_AES_128_CBC_SHA  = { 0x00,0x33 };
CipherSuite TLS_DH_anon_WITH_AES_128_CBC_SHA  = { 0x00,0x34 };

CipherSuite TLS_RSA_WITH_AES_256_CBC_SHA      = { 0x00,0x35 };
CipherSuite TLS_DH_DSS_WITH_AES_256_CBC_SHA   = { 0x00,0x36 };
CipherSuite TLS_DH_RSA_WITH_AES_256_CBC_SHA   = { 0x00,0x37 };
CipherSuite TLS_DHE_DSS_WITH_AES_256_CBC_SHA  = { 0x00,0x38 };
CipherSuite TLS_DHE_RSA_WITH_AES_256_CBC_SHA  = { 0x00,0x39 };
CipherSuite TLS_DH_anon_WITH_AES_256_CBC_SHA  = { 0x00,0x3A };

C.2. AES Cipher Suites with SHA-256​

TLS 1.2 introduces AES cipher suites using SHA-256:

CipherSuite TLS_RSA_WITH_AES_128_CBC_SHA256      = { 0x00,0x3C };
CipherSuite TLS_DH_DSS_WITH_AES_128_CBC_SHA256   = { 0x00,0x3E };
CipherSuite TLS_DH_RSA_WITH_AES_128_CBC_SHA256   = { 0x00,0x3F };
CipherSuite TLS_DHE_DSS_WITH_AES_128_CBC_SHA256  = { 0x00,0x40 };

CipherSuite TLS_RSA_WITH_AES_256_CBC_SHA256      = { 0x00,0x3D };
CipherSuite TLS_DH_DSS_WITH_AES_256_CBC_SHA256   = { 0x00,0x68 };
CipherSuite TLS_DH_RSA_WITH_AES_256_CBC_SHA256   = { 0x00,0x69 };
CipherSuite TLS_DHE_DSS_WITH_AES_256_CBC_SHA256  = { 0x00,0x6A };
CipherSuite TLS_DHE_RSA_WITH_AES_256_CBC_SHA256  = { 0x00,0x6B };
CipherSuite TLS_DH_anon_WITH_AES_128_CBC_SHA256  = { 0x00,0x6C };
CipherSuite TLS_DH_anon_WITH_AES_256_CBC_SHA256  = { 0x00,0x6D };

For example, the cipher specification parameters for TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 are:

  • Key Exchange: DHE_RSA
  • Bulk Cipher: AES_128_CBC
  • MAC Algorithm: HMAC-SHA256
  • Pseudorandom Function: PRF (SHA-256)

C.3. NULL Cipher Suites​

The following cipher suites use NULL encryption (for testing purposes only; SHOULD NOT be used in production environments):

CipherSuite TLS_RSA_WITH_NULL_SHA256 = { 0x00,0x3B };

C.4. Cipher Suite Naming Conventions​

TLS cipher suite names follow this format:

TLS_{KeyExchange}_{Authentication}_WITH_{Cipher}_{MAC}

For example:

  • TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
    • Key Exchange: DHE (Ephemeral Diffie-Hellman)
    • Authentication: RSA
    • Cipher: AES_128_CBC
    • MAC Algorithm: SHA256

C.5. Implementation Recommendations​

For TLS 1.2 implementations, it is recommended:

  1. MUST implement:

    • TLS_RSA_WITH_AES_128_CBC_SHA

  2. SHOULD implement:

    • TLS_RSA_WITH_AES_256_CBC_SHA
    • TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
    • TLS_DHE_RSA_WITH_AES_256_CBC_SHA256

  3. MAY implement:

    • Other cipher suites based on application requirements

  4. SHOULD NOT implement:

    • Anonymous (DH_anon) cipher suites (unless required for specific application scenarios)
    • NULL encryption cipher suites (except for testing purposes only)

C.6. Security Considerations​

When selecting cipher suites, consider:

  • Forward Secrecy: Prefer DHE or ECDHE cipher suites
  • Key Length: AES-256 is preferred over AES-128
  • MAC Strength: SHA-256 or stronger is preferred over SHA-1
  • Avoid Weak Algorithms: Avoid algorithms with known weaknesses such as RC4, DES, MD5

Note: For complete cipher suite definitions and detailed specifications, please refer to the full text of RFC 5246 Appendix C.