full-disclosure - Re: [FD] Should openssl accept weak DSA/DH keys with g = +/- 1 ?

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Message-ID: <CAH8yC8=ooF=SdtoWhPpuND+=67y8Xd8GeYn1BqKt3N0ZWxor_g@mail.gmail.com>
Date: Thu, 17 Apr 2014 15:22:04 -0400
From: Jeffrey Walton <noloader@...il.com>
To: Pavel Kankovsky <peak@...o.troja.mff.cuni.cz>
Cc: Full Disclosure List <fulldisclosure@...lists.org>
Subject: Re: [FD] Should openssl accept weak DSA/DH keys with g = +/- 1 ?

On Thu, Apr 17, 2014 at 12:50 PM, Pavel Kankovsky
<peak@...o.troja.mff.cuni.cz> wrote:

> Does anyone use non-safe primes for DH? Afaik any well-known moduli are
> safe. And openssl dhparam generates safe primes only.
g = 2 is not a generator though its often used. Its possible to leak
information depending on parameter selection (or only generate half
the values of the group). See, for example, "Diffie-Hellman Parameter
Check (when g = 2, must p mod 24 == 11?)",
http://crypto.stackexchange.com/questions/12961/diffie-hellman-parameter-check-when-g-2-must-p-mod-24-11.

Jeff

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