THOR - The hardware onion router

Security and privacy of data traversing internet have always been a major concern for all users. In this context, The Onion Routing (Tor) is the most successful protocol to anonymize global Internet traffic and is widely deployed as software on many personal computers or servers. In this paper, we explore the potential of modern reconfigurable devices to efficiently realize the Tor protocol on embedded devices. In particular, this targets the acceleration of the complex cryptographic operations involved in the handshake of routing nodes and the data stream encryption. Our hardware-based implementation on the Xilinx Zynq platform outperforms previous embedded solutions by more than a factor of 9 with respect to the cryptographic handshake - ultimately enabling quite inexpensive but highly efficient routers. Hence, we consider our work as a further milestone towards the development and the dissemination of low-cost and high performance onion relays that hopefully ultimately leads again to a more private Internet.