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Re: [openpgp] OpenPGP encryption block modes

Peter Gutmann <pgut001@cs.auckland.ac.nz> Thu, 11 August 2022 11:44 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] OpenPGP encryption block modes
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Date: Thu, 11 Aug 2022 11:43:54 +0000
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Subject: Re: [openpgp] OpenPGP encryption block modes
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brian m. carlson <sandals@crustytoothpaste.net> writes:

>SHA-1 is no longer considered secure, and thus we can't assume that a SHA-1
>hash of the data intrinsically indicates that it hasn't been changed.

Except that the MDC is encrypted along with the plaintext, so you can't just
brute-force a collision.  Like the HMAC construct, even if the underlying hash
function is no longer secure the overall construct is a different matter.

Peter.

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