etwork routing protocol, Kesdokan et al. introduced the Free Route and Mix Cascade concepts [7]. The former gives autonomy to the sender for dynamically choosing the trust path of the mix-nodes, while in the latter the routing paths are predefined. Mix networks introduce delays due to buffering and mixing and different padding patterns for mixing real with dummy traffic. Continuous Mixes try to avoid the delay issue by introducing fixed delay distributions for buffering and mixing. Mixes became subject to several attacks, such as timing attacks [11], statis- tical analysis of message distribution [12], statistical properties of randomly constructed routes [13,14], and packet flow correlation attacks [15,16]. Crowds [4] is a network that consists of voluntarily collaborating nodes. It is based on the idea that our anonymity can be protected better when we move ourselves within a crowd. According to [4], Crowds' web servers are unable to learn the true source of a request because it is equally likely to have originated from any member of the crowd. Even collaborating crowd members cannot distinguish the originator of a request from a member who is merely forwarding the request on behalf of another. In Crowds each user (browser) is represented in the system by a jondo process. Each message that needs anonymity enters into the Crowd node, its presence is announced via the local jondo, and is sent to another randomly chosen jondo with probability p, or to the actual server with probability 1 - p. When the server (recipient jondo) receives the message it answers using the same, forward, path. Crowds can effectively face trace back attacks, and they can mitigate collusion attacks if the users randomly select the set of forwarding jondos. Onion Routing [9] is an overlay infrastructure for providing anonymous communication over a public network. It supports anonymous connections through three phases: connection setup, data exchange, and connection ter- mination. In the setup phase the initiator creates a layered data stru