Token Binding
charter-ietf-tokbind-00-01

Web services generate various security tokens (e.g. HTTP cookies, OAuth tokens,
etc.) for web applications to access protected resources. Currently these are bearer
tokens, i.e. any party in possession of such token gains access to the protected
resource. Attackers export bearer tokens from client machines or from compromised
network connections, present these bearer tokens to Web services, and impersonate
authenticated users. Token Binding enables defense against such attacks by
cryptographically binding security tokens to a secret held by the client.

The tasks of this working group are as follows:

1. Specify the Token Binding protocol v1.0.
2. Specify the use of the Token Binding protocol in combination with HTTPS.

It is a goal of this working group to enable defense against attacks that involve
unauthorized replay of security tokens. Other issues associated with the use of
security tokens are out of scope. Another goal of this working group is to design
the Token Binding protocol such that it would be also useable with application
protocols other than HTTPS. Specifying alternative application protocols is not a
primary goal.

The main design objectives for the Token Binding protocol, in no particular order:

1. Allow applications and services to prevent unauthorized replay of security tokens.
2. Allow strong key protection, e.g. using hardware-bound keys.
3. Support both first-party (server generates a token for later use with this server)
   and federation (server generates a token for use with another server) scenarios.
4. Preserve user privacy.
5. Make the Token Binding protocol useable in combination with a variety of
   application protocols.
6. Allow the negotiation of the Token Binding protocol without additional round-trips.
7. Allow the use of multiple cryptographic algorithms, so that a variety of secure
   hardware modules with different cryptographic capabilities could be used with
   Token Binding.
8. Propose Token Binding specification that can be implemented in Web browsers
   (but is not limited to them). E.g. Web browsers require that the same bound
   security token must be presentable over multiple TLS sessions and connections.

The working group will use the following documents as a starting point for its work:

• draft-popov-token-binding-00;
• draft-balfanz-https-token-binding-00.

This WG will collaborate with other IETF WGs, in particular with the TLS, HTTPbis
and Oauth WGs.