Re: [TLS] Consensus Call: FNV vs SHA1
Simon Josefsson <simon@josefsson.org> Mon, 10 May 2010 21:48 UTC
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From: Simon Josefsson <simon@josefsson.org>
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Date: Mon, 10 May 2010 23:48:09 +0200
In-Reply-To: <20100510190954.GV9429@oracle.com> (Nicolas Williams's message of "Mon, 10 May 2010 14:09:55 -0500")
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Subject: Re: [TLS] Consensus Call: FNV vs SHA1
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Nicolas Williams <Nicolas.Williams@oracle.com> writes: > - Add a description of what happens if cached object checksums collide. > > No, the current security considerations section doesn't deal with > this, and rightly so _if_ collisions are not a security problem, but > what happens when there are collisions? Do hanshakes fail? I agree that it is important to explain this. If collisions happen, it appears that we do get slightly weaker semantics of what it means for a handshake to succeed: we aren't cryptographically certain (in the sense that there is cryptographic reduction) that the client and server agree on the data used during the handshake for cached items (CA cert list, server certificate) after the handshake has concluded. It seems a server could easily create two pairs of server certificates that results in the same FNV-1a value but are different certificates. A client connecting to a server offering a cached value for the server certificate would not know which server certificate was intended, even after completing the handshake. If correct, that seems surprising. This requires a conspiring server, so maybe it is irrelevant. This problem would be solved if the Finished message were computed over the replaced data rather than the digest value. Then any data mismatches would be detected at the TLS Finished computation, and the handshake fail. Perhaps this is simpler than introducing a cryptographic digest. It is late here, so I may be totally missing some aspect. /Simon
- Re: [TLS] Wrapping up cached info Blumenthal, Uri - 0668 - MITLL
- [TLS] Consensus Call: FNV vs SHA1 Joseph Salowey (jsalowey)
- Re: [TLS] Consensus Call: FNV vs SHA1 Simon Josefsson
- Re: [TLS] Consensus Call: FNV vs SHA1 Blumenthal, Uri - 0668 - MITLL
- Re: [TLS] Consensus Call: FNV vs SHA1 Adam Langley
- Re: [TLS] Consensus Call: FNV vs SHA1 Marsh Ray
- Re: [TLS] Consensus Call: FNV vs SHA1 Robert Dugal
- Re: [TLS] Consensus Call: FNV vs SHA1 Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Martin Rex
- Re: [TLS] Consensus Call: FNV vs SHA1 Jeffrey A. Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Paul Hoffman
- [TLS] Collisions (Re: Consensus Call: FNV vs SHA1) Nicolas Williams
- [TLS] Nico's suggestions - Re: Consensus Call: FN… Stefan Santesson
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Blumenthal, Uri - 0668 - MITLL
- [TLS] Collisions (Re: Nico's suggestions - Re: Co… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Simon Josefsson
- [TLS] Collisions (Re: Consensus Call: FNV vs SHA1) Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Simon Josefsson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Hovav Shacham
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Simon Josefsson
- Re: [TLS] Consensus Call: FNV vs SHA1 Yoav Nir
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Martin Rex
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Simon Josefsson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Michael D'Errico
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Martin Rex
- Re: [TLS] Consensus Call: FNV vs SHA1 Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Blumenthal, Uri - 0668 - MITLL
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Martin Rex
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Kemp, David P.
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Nic… Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Nic… Marsh Ray
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Con… Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Stefan Santesson
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Con… Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Stefan Santesson
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Simon Josefsson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Brian Smith
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Simon Josefsson
- Re: [TLS] Justification Adam Langley
- Re: [TLS] Justification Brian Smith
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Adam Langley
- Re: [TLS] Justification Marsh Ray
- Re: [TLS] Justification Brian Smith
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Con… Kemp, David P.
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Adam Langley
- [TLS] Use HTTP (Re: Justification) Nicolas Williams
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Yoav Nir
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Martin Rex
- Re: [TLS] Justification Marsh Ray
- Re: [TLS] Justification Stefan Santesson
- Re: [TLS] Justification Martin Rex
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Yoav Nir
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Justification Dean Anderson
- [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Simon Josefsson
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Justification Stefan Santesson
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Ben Laurie
- Re: [TLS] Wrapping up cached info Yoav Nir
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Ben Laurie
- Re: [TLS] Wrapping up cached info Martin Rex
- [TLS] Possible alternative to current cached info… Michael D'Errico
- Re: [TLS] Wrapping up cached info (and PRF WTF) Kemp, David P.
- Re: [TLS] Wrapping up cached info (and PRF WTF) Martin Rex
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info (and PRF WTF) Nicolas Williams
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Michael D'Errico
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Michael D'Errico
- Re: [TLS] Wrapping up cached info Michael D'Errico
- Re: [TLS] Wrapping up cached info Kemp, David P.
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Ben Laurie
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Martin Rex
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Nicolas Williams