[websec] TACK draft 01

Trevor Perrin <trevp@trevp.net> Wed, 26 September 2012 13:36 UTC

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From: Trevor Perrin <trevp@trevp.net>
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Subject: [websec] TACK draft 01
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Hi TLS (cc websec),

There's a new TACK draft: http://tools.ietf.org/html/draft-perrin-tls-tack-01

You can find code and other resources at http://tack.io

We'd love to get feedback or answer questions.  We'd also appreciate
advice on whether this should remain an individual submission or would
make sense as a WG document.

The main change is that we removed break signatures.  Instead, servers
may optionally publish a second tack.  Clients can form two pins for a

These changes let a server publish tacks from a new TACK key prior to
deactivating and removing the old key's tacks.  This "rollover" is a
better way to handle a compromised or suspect TACK key because it
preserves any security offered by the old key while the new one is
being introduced.

Other changes:

 * Rewrote "Client processing" to improve clarity.

 * Renamed
   "TACK" structure to "tack"
   "TACK_Extension" to "TackExtension"
   "pin_activation" field to "activation_flags"
   "TACK ID" to "key fingerprint"

 * Simplified error alerts sent by clients (and aligned with RFC 5878)

 * Deleted old section "6.2 Application-specific pinning", which was
too vague to be useful. Added new 6.1 and 6.2 discussing
considerations with different application protocols.

 * Changed server_name extension in ClientHello from SHOULD to SHALL.

 * Tweaked the Advice for Server Operators (8.1) regarding Tack expiration.