Re: [TLS] Deployment ... Re: This working group has failed
mrex@sap.com (Martin Rex) Tue, 19 November 2013 19:49 UTC
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To: Marsh Ray <maray@microsoft.com>
Date: Tue, 19 Nov 2013 20:49:48 +0100
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From: mrex@sap.com
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Cc: "tls@ietf.org" <tls@ietf.org>, Michael Staubermann <Michael.Staubermann@webolution.de>
Subject: Re: [TLS] Deployment ... Re: This working group has failed
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Marsh Ray wrote: > Martin Rex wrote: > > > > The TLSv1.1 PRF should be OK for 128-bit security strength. > > TLS 1.1 https://tools.ietf.org/html/rfc4346#page-13 > " TLS's PRF is created by splitting the secret into two halves and > using one half to generate data with P_MD5 and the other half to > generate data with P_SHA-1, then exclusive-ORing the outputs of these > two expansion functions together." > > Good for 160 bits I figure? > > TLS 1.2 https://tools.ietf.org/html/rfc5246#page-14 > " In this section, we define one PRF, based on HMAC. This PRF with the > SHA-256 hash function is used for all cipher suites defined in this > document and in TLS documents published prior to this document when > TLS 1.2 is negotiated. New cipher suites MUST explicitly specify a > PRF and, in general, SHOULD use the TLS PRF with SHA-256 or a > stronger standard hash function. > " > Sounds stronger to me. The weakest link in the chain determines the strength, not the strongest link in the chain. NIST SP800-57 provides the following guidance on strength: Bits of symm. FFC IFC ECC Hash Hash Hash security cipher (DSA/DH) (e.g.RSA) DigSig HMAC KeyDeriv 80 2TDES 1024/160 1024 160-223 SHA-1 SHA-1 SHA-1 112 3TDES 2048/224 2048 224-255 SHA-224 SHA-1 SHA-1 128 AES-128 3072/256 3072 256-383 SHA-256 SHA-1 SHA-1 192 AES-192 7680/384 7680 384-511 SHA-384 SHA-224 SHA-224 256 AES-256 15360/512 15360 512+ SHA-512 SHA-256 SHA-256 So for use with RSA-2048 certs and AES128 encryption, the TLSv1.0/v1.1 PRF should be OK. You may want to look at how many signatures in certificates, CRLs, OCSP, etc. still use SHA-1, and where this gets you in the above table. -Martin
- [TLS] This working group has failed Watson Ladd
- [TLS] Deployment ... Re: This working group has f… Hannes Tschofenig
- Re: [TLS] Deployment ... Re: This working group h… Taylor Hornby
- Re: [TLS] This working group has failed SM
- Re: [TLS] This working group has failed Ralph Holz
- Re: [TLS] Deployment ... Re: This working group h… Hannes Tschofenig
- Re: [TLS] Deployment ... Re: This working group h… Yoav Nir
- Re: [TLS] Deployment ... Re: This working group h… Hannes Tschofenig
- Re: [TLS] This working group has failed Salz, Rich
- Re: [TLS] Deployment ... Re: This working group h… Mark Nottingham
- Re: [TLS] Deployment ... Re: This working group h… Kyle Hamilton
- Re: [TLS] Deployment ... Re: This working group h… Juho Vähä-Herttua
- Re: [TLS] Deployment ... Re: This working group h… Watson Ladd
- Re: [TLS] Deployment ... Re: This working group h… Salz, Rich
- Re: [TLS] Deployment ... Re: This working group h… Watson Ladd
- Re: [TLS] Deployment ... Re: This working group h… Salz, Rich
- Re: [TLS] Deployment ... Re: This working group h… Andrei Popov
- Re: [TLS] Deployment ... Re: This working group h… Martin Rex
- Re: [TLS] Deployment ... Re: This working group h… Martin Rex
- Re: [TLS] Deployment ... Re: This working group h… Watson Ladd
- Re: [TLS] Deployment ... Re: This working group h… Geoffrey Keating
- Re: [TLS] Deployment ... Re: This working group h… Michael Staubermann
- Re: [TLS] Deployment ... Re: This working group h… Martin Rex
- Re: [TLS] Deployment ... Re: This working group h… Joshua Davies
- Re: [TLS] Deployment ... Re: This working group h… Martin Rex
- Re: [TLS] Deployment ... Re: This working group h… Martin Rex
- Re: [TLS] Deployment ... Re: This working group h… Andy Lutomirski
- Re: [TLS] Deployment ... Re: This working group h… Kirils Solovjovs
- Re: [TLS] Deployment ... Re: This working group h… Andy Wilson
- Re: [TLS] Deployment ... Re: This working group h… Marsh Ray
- Re: [TLS] Deployment ... Re: This working group h… Ralf Skyper Kaiser
- Re: [TLS] Deployment ... Re: This working group h… Ben Laurie
- [TLS] TLS protocol version intolerance [Was: Re: … Ivan Ristić
- Re: [TLS] Deployment ... Re: This working group h… Zooko Wilcox-OHearn
- Re: [TLS] TLS protocol version intolerance [Was: … Michael Sweet
- Re: [TLS] TLS protocol version intolerance [Was: … Eric Rescorla
- Re: [TLS] Deployment ... Re: This working group h… Martin Rex
- Re: [TLS] Deployment ... Re: This working group h… Andy Lutomirski
- Re: [TLS] Deployment ... Re: This working group h… Martin Rex
- [TLS] multiple clients in one process (was: Re: D… Patrick Pelletier
- Re: [TLS] multiple clients in one process (was: R… Andy Lutomirski
- Re: [TLS] multiple clients in one process (was: R… Daniel Kahn Gillmor
- Re: [TLS] multiple clients in one process (was: R… Nico Williams
- Re: [TLS] multiple clients in one process (was: R… Nikos Mavrogiannopoulos
- Re: [TLS] multiple clients in one process (was: R… Andy Lutomirski