Receiver anonymity via Incomparable Public Keys

We describe a new method for protecting the anonymity of message receivers in an untrusted network. Surprisingly, existing methods fail to provide the required level of anonymity for receivers (although those methods do protect sender anonymity). Our method relies on the use of multicast, along with a novel cryptographic primitive that we call an Incomparable Public Key cryptosystem, which allows a receiver to efficiently create many anonymous "identities" for itself without divulging that these separate "identities" actually refer to the same receiver, and without increasing the receiver's workload as the number of identities increases. We describe the details of our method, along with a prototype implementation.