quantify the anonymity achievable in a multihop network. Metrics of anonymity that have been proposed [8, 9] in the context of Mix networks are typically based on anonymity sets of individual packets. The anonymity set refers to the Freenet [17] and Tarzan [18] are examples of peer-to-peer anonymizing systems. The approach we adopt is

Figure 1: Tarzan Architecture Overview Tarzan participants, inquisitive Internet servers, and observers who can see traffic on a limited number of network links. The larger purpose of Tarzan is to support a systems-engineering position: anonymity can be built-in as an underlying transport layer, transparent Presentation on: Tarzan: A Peer-to-Peer Anonymizing Steffen Schott Tarzan: A P2P Anonimizing Network Layer 5 Achieving Anonymity Techniques used to achieve anonymity: • Flexible mixes for tunneling within peers-Not like Chaumian Mixes • Onion routing style encryption-To avoid traceability of path and content disclosure • Unforeseen peer selection A Peer-to-Peer Anonymizing Network Layer

Besides anonymity, the basic design goals for a network-layer anonymity system are scalability and performance. With respect to scalability, a network-layer anonymity sys-tem minimizes the amount of state kept on network routers who possess limited high-speed memory. With respect to performance, a network-layer anonymity system should of-

November 20, 2002 Tarzan: a Peer-to-Peer Anonymizing Network Layer Page 19 • No distinction between anon proxies and clients – Peer-to-peer model • Anonymity against corrupt relays

This anonymous network layer could seamlessly replace the current communications channel, and it could continue to offer anonymity and availability even while components fail maliciously. This thesis proposes Tarzan, a peer-to-peer anonymous IP network overlay. Because it provides IP service, Tarzan is general-purpose and transparent to

Survey of Anonymity and Authentication in P2P Networks