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Re: [TLS] AD review of draft-ietf-tls-negotiated-ff-dhe-08

Peter Gutmann <pgut001@cs.auckland.ac.nz> Wed, 15 April 2015 14:43 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "<tls@ietf.org>" <tls@ietf.org>
Thread-Topic: [TLS] AD review of draft-ietf-tls-negotiated-ff-dhe-08
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Date: Wed, 15 Apr 2015 14:43:34 +0000
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Subject: Re: [TLS] AD review of draft-ietf-tls-negotiated-ff-dhe-08
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Santiago Zanella <szanella@gmail.com> writes:

>A current full IPv4 survey of groups used for FFDHE shows that the 2048-bit
>MODP group from RFC3526 is the 5th most common (and the most common with a
>modulus longer than 1024 bits): roughly 7.8% of over 10M hosts use it. For
>comparison, 8.7% use IKE 1024-bit MODP group. The other MODP groups in
>RFC3526 are used only marginally.

So... if 8.7% is the most widely-used group (since you qualify the 7.8% one
with "the most common with a modulus longer than 1024 bits"), that means the
most common group is one that the ff-dhe draft doesn't allow you to specify,
and the most common group with a modulus longer than 1024 bits is... another
one that the ff-dhe draft doesn't allow you to specify.

Peter.

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