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Re: [openpgp] RSA-PSS and RSA-OAEP for v5

Peter Gutmann <pgut001@cs.auckland.ac.nz> Sun, 28 February 2021 03:50 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "brian m. carlson" <sandals@crustytoothpaste.net>, "openpgp@ietf.org" <openpgp@ietf.org>
Thread-Topic: [openpgp] RSA-PSS and RSA-OAEP for v5
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Date: Sun, 28 Feb 2021 03:49:45 +0000
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Subject: Re: [openpgp] RSA-PSS and RSA-OAEP for v5
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brian m. carlson <sandals@crustytoothpaste.net> writes:

>I'm interested in seeing if we can require v5 SKESK packets with RSA use RSA-
>OAEP with SHA-256 and MGF1-SHA-256 and require that v5 signatures with RSA
>use RSA-PSS, with the MGF using the same digest as the signature.

Apart from adding a huge amount of complexity and potential interop problems,
you're not really gaining anything by this that isn't already addressed by
"MUST use encode-them-memcmp() for signatures".  PKCS #1 signing is perfectly
secure if you do that, and PKCS #1 encryption doesn't matter much because PGP
isn't likely to be used in situations where it acts as an online million-
message oracle.

See also my post to the cryptography list last year about all the games an
attacker can play with OAEP because the parameters aren't authenticated and
therefore attacker-controlled.

Peter.

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