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Re: [quicwg/base-drafts] The QUIC-TLS draft should define anti-forgery limits for packet lengths up to 2^16 (#3701)

Martin Thomson <notifications@github.com> Mon, 28 September 2020 22:19 UTC

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Date: Mon, 28 Sep 2020 15:19:50 -0700
From: Martin Thomson <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] The QUIC-TLS draft should define anti-forgery limits for packet lengths up to 2^16 (#3701)
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After thinking about this a lot, I prefer not to do anything.  For several reasons, but mostly because I think that a mechanical protection is an overreaction to this situation.

The target limits are arbitrary.  The degradation here is *at worst* an increase in attacker advantage from 2^-57 to 2^-53.  That's for CCM.  The GCM and Poly1305 numbers scale linearly, so the change is to 2^-55.

I could see a way to sharpen the text, but mandating use of the UDP size limit to do this seems unnecessary.  Suggesting that usage - for the paranoid - would be OK.

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