I’ve discovered some attacks against the original PipeNet design. The new protocol, PipeNet 1.1, should fix the weaknesses. PipeNet 1.1 uses layered sequence numbers and MACs. This prevents a collusion between a receiver and a subset of switches from tracing the caller by modifying or swaping packets and then watching for garbage.
A description of PipeNet 1.1 is available at
http://www.eskimo.com/~weidai.
Also available there is a description of b-money, a new protocol for monetary exchange and contract enforcement for pseudonyms.
Please direct all follow-up discussion of these protocols to cypherpunks.