Solving Performance Issues in Anonymization Overlays with a L3 approach

Anonymization (Mix) networks are based on the delivery of messages through a sequence of overlay hops devised to void end-to-end linkage of the information, thus protecting users' identities (when needed) and privacy. Most Mix networks are based on hops built either on TLS or directly built by proprietary protocols. In the first part of this paper we analyze the methodology chosen so far to build Mix networks and Tor in particular and show, through experiments supported by a theoretical explanation, that overlays based on congestion-controlled transport level tunnels may incur in devastating performance degradation. The second part of the paper is devoted to the discussion of anonymous networks based on layer-3 standard solutions, like IPsec and NATs, and to the description of a Linux-based implementation that is scalable, performing and fulfills all anonymity requirements.