Re: [TLS] Short Ephermal Diffie-Hellman keys
Eric Rescorla <ekr@networkresonance.com> Sun, 03 June 2007 15:08 UTC
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Date: Sun, 03 Jun 2007 08:07:10 -0700
From: Eric Rescorla <ekr@networkresonance.com>
To: Bodo Moeller <bmoeller@acm.org>
Subject: Re: [TLS] Short Ephermal Diffie-Hellman keys
In-Reply-To: <20070515224351.GA27872@tau.invalid>
References: <op.tsa3n9ttqrq7tp@nimisha.oslo.opera.com> <4648AEA2.3020506@bolyard.com> <20070515130804.GA15682@tau.invalid> <4649D2FD.2020309@drh-consultancy.demon.co.uk> <4649E35B.4030809@bolyard.com> <20070515202726.GA24732@tau.invalid> <0MKu60-1Ho53w3DRn-0003jg@mx.kundenserver.de> <20070515224351.GA27872@tau.invalid>
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At Wed, 16 May 2007 00:43:51 +0200, Bodo Moeller wrote: > I'd suggest stating in the TLS specification that 'q' can only be > included in the ServerKeyExchange message for the case of prime-order > subgroups. These are what you'd usually use, except sometimes if the > DH subgroup is nearly as large as 'p', which is a case where knowing > 'q' doesn't provide significant benefits anyhow. So, I'm no DH expert, but my understanding is that there are three common cases: 1. Randomly generated p with no special structure 2. Sophie-Germain primes where q is about p/2. 3. DSA-style groups where q<<p. Only in the last case does carrying around q offer much benefit. Is this common enough that it's worth changing the spec? It was my understanding that we mostly encouraged people to use S-G primes in any case. -Ekr _______________________________________________ TLS mailing list TLS@lists.ietf.org https://www1.ietf.org/mailman/listinfo/tls
- [TLS] Short Ephermal Diffie-Hellman keys Yngve N. Pettersen (Developer Opera Software ASA)
- Re: [TLS] Short Ephermal Diffie-Hellman keys Mike
- Re: [TLS] Short Ephermal Diffie-Hellman keys Nelson B Bolyard
- Re: [TLS] Short Ephermal Diffie-Hellman keys Yngve N. Pettersen (Developer Opera Software ASA)
- RE: [TLS] Short Ephermal Diffie-Hellman keys Pasi.Eronen
- Re: [TLS] Short Ephermal Diffie-Hellman keys Dr Stephen Henson
- [TLS] Re: Short Ephermal Diffie-Hellman keys Simon Josefsson
- Re: [TLS] Short Ephermal Diffie-Hellman keys Bodo Moeller
- Re: [TLS] Short Ephermal Diffie-Hellman keys jimmy
- Re: [TLS] Short Ephermal Diffie-Hellman keys Bodo Moeller
- RE: [TLS] Re: Short Ephermal Diffie-Hellman keys Pasi.Eronen
- Re: [TLS] Short Ephermal Diffie-Hellman keys Dr Stephen Henson
- [TLS] Re: Short Ephermal Diffie-Hellman keys Simon Josefsson
- Re: [TLS] Short Ephermal Diffie-Hellman keys Nelson B Bolyard
- Re: [TLS] Short Ephermal Diffie-Hellman keys Bodo Moeller
- Re: [TLS] Short Ephermal Diffie-Hellman keys Russ Housley
- Re: [TLS] Short Ephermal Diffie-Hellman keys Bodo Moeller
- Re: [TLS] Short Ephermal Diffie-Hellman keys Peter Gutmann
- [TLS] RE: Short Ephermal Diffie-Hellman keys Pasi.Eronen
- Re: [TLS] Short Ephermal Diffie-Hellman keys Eric Rescorla
- Re: [TLS] Short Ephermal Diffie-Hellman keys Bodo Moeller
- Re: [TLS] Short Ephermal Diffie-Hellman keys Russ Housley
- Re: [TLS] Short Ephermal Diffie-Hellman keys Bodo Moeller
- Re: [TLS] Short Ephermal Diffie-Hellman keys Russ Housley
- Re: [TLS] Short Ephermal Diffie-Hellman keys Peter Gutmann