Re: [Cfrg] [TLS] Closing out tls1.3 "Limits on key usage" PRs (#765/#769)

Yoav Nir <ynir.ietf@gmail.com> Tue, 14 February 2017 22:00 UTC

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From: Yoav Nir <ynir.ietf@gmail.com>
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Date: Tue, 14 Feb 2017 23:59:57 +0200
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To: Atul Luykx <Atul.Luykx@esat.kuleuven.be>
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Subject: Re: [Cfrg] [TLS] Closing out tls1.3 "Limits on key usage" PRs (#765/#769)
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> On 14 Feb 2017, at 23:52, Atul Luykx <Atul.Luykx@esat.kuleuven.be> wrote:
> 
>> Why is that 2^48 input blocks rather than 2^34.5 input blocks?
> Because he wants to lower the security level. The original text recommends switching at 2^{34.5} input blocks, corresponding to a success probability of 2^{-60}, whereas his text recommends switching at 2^{48} blocks, corresponding to a success probability of 2^{-32}.

OK, missed that.

So I’m in favor of switching the phrasing to be about blocks rather than maximum-sized records, but not in favor of lowering the security level.

Yoav