Re: [Cfrg] Unknown order DH groups, e.g. as in RFC3526.
Andrey Jivsov <crypto@brainhub.org> Fri, 08 March 2019 23:16 UTC
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From: Andrey Jivsov <crypto@brainhub.org>
Date: Fri, 08 Mar 2019 15:16:32 -0800
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To: "Scott Fluhrer (sfluhrer)" <sfluhrer@cisco.com>
Cc: "cfrg@irtf.org" <cfrg@irtf.org>
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Subject: Re: [Cfrg] Unknown order DH groups, e.g. as in RFC3526.
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Sorry, a correction: https://tools.ietf.org/html/rfc7919 is the RFC that defines safe primes, and thus the group order is (p-1)/2 for each of them. What's the group order for random primes in https://tools.ietf.org/html/rfc3526 ? Do you mean the composite group order p-1 with potentially unpleasant many-small-factors factorization? On Fri, Mar 8, 2019 at 2:59 PM Scott Fluhrer (sfluhrer) <sfluhrer@cisco.com> wrote: > I suspect you mistyped the RFC number you meant; instead of saying that > the groups listed in RFC3526 didn’t specify an order (they do), you meant > to talk about the groups in some other RFC… > > > > *From:* Cfrg <cfrg-bounces@irtf.org> *On Behalf Of * Andrey Jivsov > *Sent:* Friday, March 08, 2019 5:44 PM > *To:* cfrg@irtf.org > *Subject:* [Cfrg] Unknown order DH groups, e.g. as in RFC3526. > > > > Greetings. > > > > A quick question on DH primes. > > > > The IKE DH groups document didn't specify the group order > https://tools.ietf.org/html/rfc3526 . > > > > This is in contrast to https://tools.ietf.org/html/rfc3526 that uses safe > primes. > > > > Is my understanding correct that, as a general rule, these primes should > not be used, e.g. where a contributory behaviour of DH is needed? The issue > here is that a random element, received from a peer, can be in any > subgroup, possibly in a subroup with lower security than 128 bits, and > there is no way to verify this efficiently. > > > > Thank you. >
- [Cfrg] Unknown order DH groups, e.g. as in RFC352… Andrey Jivsov
- Re: [Cfrg] Unknown order DH groups, e.g. as in RF… Scott Fluhrer (sfluhrer)
- Re: [Cfrg] Unknown order DH groups, e.g. as in RF… Andrey Jivsov
- Re: [Cfrg] Unknown order DH groups, e.g. as in RF… Markku-Juhani Olavi Saarinen
- Re: [Cfrg] Unknown order DH groups, e.g. as in RF… Markku-Juhani Olavi Saarinen