Re: [CFRG] RSA PSS Salt Length for HTTP Message Signatures

Neil Madden <neil.e.madden@gmail.com> Sat, 29 May 2021 12:27 UTC

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From: Neil Madden <neil.e.madden@gmail.com>
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Cc: Justin Richer <jricher@mit.edu>, IRTF CFRG <Cfrg@irtf.org>
Date: Sat, 29 May 2021 13:26:57 +0100
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To: Peter Gutmann <pgut001@cs.auckland.ac.nz>
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Subject: Re: [CFRG] RSA PSS Salt Length for HTTP Message Signatures
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On 29 May 2021, at 10:22, Peter Gutmann <pgut001@cs.auckland.ac.nz> wrote:
> 
> Neil Madden <neil.e.madden@gmail.com> writes:
> 
>> By this do you mean *constant-time* memcmp? Otherwise that seems something
>> quite easy to get wrong.
> 
> You're doing a memcmp() on known, public data, there's nothing to leak so no
> need for a constant-time memcmp().

I was thinking of the fault attack mitigation technique where you sign twice and compare. I guess you’re talking about verification instead. 

— Neil