On the Power of Anonymous One-Way Communication

We consider a population of anonymous processes communicating via anonymous message-passing, where the recipient of each message is chosen by an adversary and the sender is not identified to the recipient. Even with unbounded message sizes and process states, such a system can compute only limited predicates on inputs held by the processes. In the finite-state case, we show how the exact strength of the model depends critically on design choices that are irrelevant in the unbounded-state case, such as whether messages are delivered immediately or after a delay, whether a sender can record that it has sent a message, and whether a recipient can queue incoming messages, refusing to accept new messages until it has had a chance to send out messages of its own. These results may have implications for the design of distributed systems where processor power is severely limited, as in sensor networks.