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Re: [tcpinc] Eric Rescorla's Discuss on draft-ietf-tcpinc-tcpeno-13: (with DISCUSS and COMMENT)

Kyle Rose <krose@krose.org> Sun, 12 November 2017 07:19 UTC

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From: Kyle Rose <krose@krose.org>
Date: Sun, 12 Nov 2017 15:19:23 +0800
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To: Eric Rescorla <ekr@rtfm.com>
Cc: "Black, David" <David.Black@dell.com>, The IESG <iesg@ietf.org>, "draft-ietf-tcpinc-tcpeno@ietf.org" <draft-ietf-tcpinc-tcpeno@ietf.org>, "tcpinc-chairs@ietf.org" <tcpinc-chairs@ietf.org>, "tcpinc@ietf.org" <tcpinc@ietf.org>
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Subject: Re: [tcpinc] Eric Rescorla's Discuss on draft-ietf-tcpinc-tcpeno-13: (with DISCUSS and COMMENT)
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On Sun, Nov 12, 2017 at 1:13 PM, Eric Rescorla <ekr@rtfm.com> wrote:
> On Sun, Nov 12, 2017 at 5:08 AM, Black, David <David.Black@dell.com> wrote:
>> - Encryption: The intent is - don't use anything weaker than AES-128,
>> e.g., don't even think about using 3DES.  The concern is how to write that
>> requirement in a way that would survive hypothetical discovery of a
>> catastrophic cryptanalytic attack on AES-128.
>
>
> Or even a small one. I mean, what does this say about Curve25519 or 4Q.

I think this is actually the issue driving the vagueness of the
requirement: e.g., if some hypothetical attack against AES-128 reduced
security by a few bits. The intent, as David suggests, is to prohibit
the use of something like DES, not to prohibit a 128-bit cipher with
only (say) 125 bits of security.

Kyle

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