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Re: [TLS] WGLC for draft-ietf-tls-ecdhe-psk-aead

Martin Thomson <martin.thomson@gmail.com> Wed, 21 December 2016 01:24 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Wed, 21 Dec 2016 12:24:53 +1100
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To: Russ Housley <housley@vigilsec.com>
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Cc: IETF TLS <tls@ietf.org>
Subject: Re: [TLS] WGLC for draft-ietf-tls-ecdhe-psk-aead
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On 21 December 2016 at 01:45, Russ Housley <housley@vigilsec.com> wrote:
> I am curious about the choice of hash function for TLS_ECDHE_PSK_WITH_AES_256_CCM_8_SHA256.  All of the other AES-256 ciphersuites defined in this document that use SHA-384.  Why does the one with a truncated authentication tag use SHA-256?

I would go further than Russ and challenge the value of the
ciphersuite entirely.  Though I think that we've already discussed
this before, several times.

For some reason I can't remember ever having had my mind changed on
this point, though I think John pointed at the larger key size having
some advantage with respect to (mumble), even if you aren't concerned
about active forgery.

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