# TLS 1.2 PRF Cipher Suite Specification

I am upgrading our assembler SSL/TLS implementation to support TLS 1.2 and am reviewing RFC5246 specification for TLS 1.2. It states that the PRF is now part of the cipher suite specification but later also states that all cipher suites defined in this document use P_SHA256. Does that for example mean when using CipherSuite TLS_RSA_WITH_AES_128_CBC_SHA = { 0x00,0x2F }; that is must use the TLS PRF with SHA-256 when TLS 1.2 is negotiated?

-
Yes, RFC 5246 states that: The MD5/SHA-1 combination in the pseudorandom function (PRF) has been replaced with cipher-suite-specified PRFs. All cipher suites in this document use P_SHA256. . This also includes the cipher suite you give. If a cipher suite should not use the TLS_PRF(with SHA-256) defined in RFC 5246, then it must be stated explicitly in the definition of that cipher suite. – Makif May 4 at 5:38