Hi, In view of the recent thread ("That 70's Crypto Show") turning into yet another call for protocol building blocks -- and Wei Dai pointing out very sensibly the problems involved in turning protocols into building blocks -- I think it might help to compile a list of our favorite protocols and problems. Then maybe we can see what common components they share, if any. Finally see if we can make some progress in overcoming the problems that Wei Dai mentioned, or if it really isn't worth the bother. I can think of key exchange - See P1363 project on this digital cash - Chaum fair exchange, 2party only - Merkle, Goldreich et al, others fair exchange, 3rd party - Micali's "invisible post offices" anonymous e-mail - Chaum anonymous web surfing - Freedom/Onion Routing/Crowds/Hordes abuse-free contract singing - Jakobsson/Garay/McKenzie middlemen and contracts - Franklin and Durfee what else? -David