Sphinx: A Compact and Provably Secure Mix Format

Sphinx is a cryptographic message format used to relay anonymized messages within a mix network. It is more compact than any comparable scheme, and supports a full set of security features: indistinguishable replies, hiding the path length and relay position, as well as providing unlinkability for each leg of the message's journey over the network. We prove the full cryptographic security of Sphinx in the random oracle model, and we describe how it can be used as an efficient drop-in replacement in deployed remailer systems.