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Re: [quicwg/base-drafts] Why does stateless reset have to be checked after MAC failure (#2152)

Kazuho Oku <notifications@github.com> Tue, 27 August 2019 07:52 UTC

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From: Kazuho Oku <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Why does stateless reset have to be checked after MAC failure (#2152)
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While I agree that endpoints should not leak information that let's the attacker guess a valid token value, I am not sure if we need to require constant time comparison, as suggested by #2993.

I think that the practical defense would be mix a secret seed securely into the hash key (e.g., by using HMAC), much like we do for hash tables to prevent DoS collision attacks. Assuming that we mix a secure seed, the attacker would not be possible to deduce information from the response time of the hash table.

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