Re: [TLS] What would make TLS cryptographically better for TLS 1.3
Nico Williams <nico@cryptonector.com> Fri, 01 November 2013 23:13 UTC
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Date: Fri, 01 Nov 2013 18:13:45 -0500
From: Nico Williams <nico@cryptonector.com>
To: Dan Harkins <dharkins@lounge.org>
Message-ID: <20131101231342.GG32733@gmail.com>
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Subject: Re: [TLS] What would make TLS cryptographically better for TLS 1.3
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On Fri, Nov 01, 2013 at 03:38:06PM -0700, Dan Harkins wrote: > On Fri, November 1, 2013 2:34 pm, Robert Ransom wrote: > > On 10/31/13, Nico Williams <nico@cryptonector.com> wrote: > > > >> - Many fewer nonce bytes and random IVs where possible. Nonce payloads > >> should be sent when needed, if needed. For example, to derive a > >> session key from an DHE shared secret one does not really need > >> nonces. This means that counter modes are better, for example, than > >> CBC modes. > > > > If the server sends a nonce during a DHE/ECDHE key exchange, the > > server can safely reuse its DH keypair for multiple clients with no > > further design or implementation considerations. > > I don't believe that's true. If the server reuses its ephemeral D-H key > then caveat emptor applies-- it should validate the client's public key, Agreed. A small nonce should suffice for key derivation if either party reuses their supposedly-ephemeral DH keys. By "small" I mean "not nearly as large as 32 bytes, i.e., not enough to suffice for a Dual_EC-type backdoored RNG attack". The party reusing a key should send some such small nonce, possibly a 64-bit nonce. In any case, the client ought not be reusing ephemeral DH keys, and any server that does should be rotating them often (like SSHv1 used to). > regardless of whether a nonce is sent or not. For some curves there's no need to validate the client's public key. Nico --
- [TLS] What would make TLS cryptographically bette… Watson Ladd
- Re: [TLS] What would make TLS cryptographically b… Nico Williams
- Re: [TLS] What would make TLS cryptographically b… Dan Harkins
- Re: [TLS] What would make TLS cryptographically b… Nikos Mavrogiannopoulos
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Nico Williams
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Dan Harkins
- Re: [TLS] What would make TLS cryptographically b… Watson Ladd
- Re: [TLS] What would make TLS cryptographically b… Nico Williams
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Nico Williams
- Re: [TLS] What would make TLS cryptographically b… Dan Harkins
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Dan Harkins
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Watson Ladd
- [TLS] removal of nonces [was: What would make TLS… Nikos Mavrogiannopoulos
- Re: [TLS] What would make TLS cryptographically b… Andy Lutomirski
- Re: [TLS] What would make TLS cryptographically b… Nico Williams
- Re: [TLS] removal of nonces [was: What would make… Nico Williams
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Ralf Skyper Kaiser
- Re: [TLS] What would make TLS cryptographically b… Ralf Skyper Kaiser
- Re: [TLS] What would make TLS cryptographically b… Nikos Mavrogiannopoulos
- Re: [TLS] What would make TLS cryptographically b… Yoav Nir
- Re: [TLS] What would make TLS cryptographically b… Robert Ransom
- Re: [TLS] What would make TLS cryptographically b… Ralf Skyper Kaiser
- Re: [TLS] What would make TLS cryptographically b… Ralf Skyper Kaiser
- Re: [TLS] What would make TLS cryptographically b… Watson Ladd
- Re: [TLS] What would make TLS cryptographically b… Yoav Nir
- Re: [TLS] What would make TLS cryptographically b… Ralf Skyper Kaiser
- Re: [TLS] What would make TLS cryptographically b… Martin Rex
- Re: [TLS] What would make TLS cryptographically b… Ralf Skyper Kaiser
- Re: [TLS] What would make TLS cryptographically b… Jeff Jarmoc
- Re: [TLS] What would make TLS cryptographically b… Nico Williams
- Re: [TLS] What would make TLS cryptographically b… Yoav Nir
- Re: [TLS] What would make TLS cryptographically b… Johannes Merkle
- Re: [TLS] What would make TLS cryptographically b… Dan Harkins
- Re: [TLS] What would make TLS cryptographically b… Yoav Nir
- Re: [TLS] What would make TLS cryptographically b… Santosh Chokhani
- Re: [TLS] What would make TLS cryptographically b… Ralf Skyper Kaiser