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Re: [TLS] Using RSA PSS in TLS

Peter Gutmann <pgut001@cs.auckland.ac.nz> Sun, 18 January 2015 02:47 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "<tls@ietf.org>" <tls@ietf.org>
Thread-Topic: [TLS] Using RSA PSS in TLS
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Date: Sun, 18 Jan 2015 02:47:38 +0000
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Subject: Re: [TLS] Using RSA PSS in TLS
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Watson Ladd <watsonbladd@gmail.com> writes:

>RSA-OEAP has similar error oracle issues,

That's one thing I noticed when I implemented it some time ago, OAEP is an
absolute goldmine (or minefield) of oracles.  PKCS 1.5 is just a
straightforward walk-down-the-byte-string check while OAEP requires multiple
complex steps to decode/check it, even with very careful ordering of the
checks you do to make sure there's very little time difference between them
(including deferring checks to cluster them around the same time and similar
steps) you can't really create an oracle-free implementation.

Peter.

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