[websec] TACK draft 01

[Trevor Perrin <[e-mail]>]

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.


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

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.


Trevor