I am currently working on WS-Trust Negotiation/Challenge for Picketlink, as mentioned here http://community.jboss.org/thread/155702
It is in a very early stage merely proof of concept.
I think it is good idea to have a interface STSContext and maybe a WSTrustNegotiationContext since there is a lot of extra communication between client and server. I think it makes sense to maybe distinguish WSTrust with and without Negotiation/Challenge.
I would like to contribute to PL especially the WSTrust-Negotioation/Challenge Handling.
Currently my code is in a proof-of-concept state for Idemixtoken issuing, where I needed WSTrust-Negotiation/Challenge handling.
I added a lot of code directly into some classes for this, without changing the overall structure of PL.
I would like to add redesigned parts of it, so it fits nicer into PL.