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Re: [saag] Possible backdoor in RFC 5114

Peter Gutmann <pgut001@cs.auckland.ac.nz> Fri, 07 October 2016 02:42 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Yoav Nir <ynir.ietf@gmail.com>, Watson Ladd <watsonbladd@gmail.com>
Thread-Topic: [saag] Possible backdoor in RFC 5114
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Date: Fri, 07 Oct 2016 02:42:50 +0000
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Cc: Security Area Advisory Group <saag@ietf.org>
Subject: Re: [saag] Possible backdoor in RFC 5114
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Yoav Nir <ynir.ietf@gmail.com> writes:

>It has never been explained in what way a 2048-bit MODP Group with 224-bit
>Prime Order Subgroup is better than a 2048-bit MODP Group without one.
>Consequently everyone uses the regular 2048-bit MODP from RFC 3526 ([2]) if
>they’re not using ECDHE groups.

My thoughts exactly.  Given that with sizeof( p ) == sizeof( g ) these are
probably the least efficient DH parameters ever published, the whole RFC just
screams "don't use me".  Does it even need to be actively deprecated?

Peter.

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