Re: [TLS] New draft: draft-ietf-tls-tls13-14.txt

Peter Gutmann <pgut001@cs.auckland.ac.nz> Tue, 19 July 2016 06:59 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: David McGrew <mcgrew@cisco.com>, "Dang, Quynh (Fed)" <quynh.dang@nist.gov>
Thread-Topic: [TLS] New draft: draft-ietf-tls-tls13-14.txt
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Date: Tue, 19 Jul 2016 06:58:52 +0000
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Subject: Re: [TLS] New draft: draft-ietf-tls-tls13-14.txt
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David McGrew <mcgrew@cisco.com>; writes:

>What is especially cool about counter mode encryption is how its real world
>security degrades more gracefully than CBC mode encryption.

Uhh... how does CTR "degrade gracefully" compared to CBC?  With CTR, any kind
of problem with the IV/CTR leads to a catastrophic loss of security.  With CBC,
even the worst-case IV abuse you can apply, setting it to all zeroes, just
degrades the mode to ECB.

(There have been a number of instances of CTR, or at least GCM, failures
already, and I doubt we've seen the last of it.  It's RC4 all over again).

Peter.