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Data transfer over TCP/IP provides no privacy for network users. Previous research in anonymity has focused on the provision of initiator anonymity. We explore methods of adapting existing initiator-anonymous protocols to provide responder anonymity and mutual anonymity. We present anonymous peer-to-peer file sharing (APFS) protocols, which provide mutual anonymity for peer-to-peer file sharing. APFS addresses the problem of long-lived Internet services that may outlive the degradation present in current anonymous protocols. One variant of APFS makes use of unicast communication, but requires a central coordinator to bootstrap the protocol. A second variant takes advantage of multicast routing to remove the need for any central coordination point. We compare the TCP performance of the APFS protocol to existing overt file sharing systems such as Napster. In providing anonymity, APFS can double transfer times and requires that additional traffic be carried by peers, but this overhead is constant with the size of the session.