Improving the Sphinx Mix Network

Secure mix networks consider the presence of multiple nodes that relay encrypted messages from one node to another in such a way that anonymous communication can be achieved. We consider the Sphinx mix formatting protocol by Danezis and Goldberg (IEEE Security and Privacy 2009), and analyze its use of symmetric-key cryptographic primitives. We scrutinize the reliance on multiple distinct primitives, as well as the use of the ancient LIONESS cipher, and suggest various paths towards improving the security and efficiency of the protocol.