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Date: Wed, 9 Apr 2014 13:57:45 +0000 From: Peter Gutmann <pgut001@...auckland.ac.nz> To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net> Subject: Re: [PHC] Deriving multiple keys (was RE: Mechanical tests) Thomas Pornin <pornin@...et.org> writes: >In TLS (see section 6.3 of RFC 5246), the symmetric keys are derived from the >"master secret" with a single PRF call: > > When keys and MAC keys are generated, the master secret is used as an > entropy source. > > To generate the key material, compute > > key_block = PRF(SecurityParameters.master_secret, > "key expansion", > SecurityParameters.server_random + > SecurityParameters.client_random); Oops, yeah, I was thinking of the general use of the label in the PRF, e.g. the MAC/Finished-message "client finished" vs. "server finished", and then for key expansion "master secret" vs. "key expansion", but you're right, the keying material is from a single application of the PRF. Peter.
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