The Cooperative File System (CFS) is a new peer-to-peer readonly storage system that provides provable guarantees for the efficiency, robustness, and load-balance of file storage and retrieval. CFS does this with a completely decentralized architecture that can scale to large systems. CFS servers provide a distributed hash table (DHash) for block storage. CFS clients interpret DHash blocks as a file system. DHash distributes and caches blocks at a fine granularity to achieve load balance, uses replication for robustness, and decreases latency with server selection. DHash finds blocks using the Chord location protocol, which operates in time logarithmic in the number of servers. CFS is implemented using the SFS file system toolkit and runs on Linux, OpenBSD, and FreeBSD. Experience on a globally deployed prototype shows that CFS delivers data to clients as fast as FTP. Controlled tests show that CFS is scalable: with 4,096 servers, looking up a block of data involves contacting only seven servers. The tests also demonstrate nearly perfect robustness and unimpaired performance even when as many as half the servers fail.

We present Tor, a circuit-based low-latency anonymous communication service. This second-generation Onion Routing system addresses limitations in the original design. Tor adds perfect forward secrecy, congestion control, directory servers, integrity checking, configurable exit policies, and a practical design for rendezvous points. Tor works on the real-world Internet, requires no special privileges or kernel modifications, requires little synchronization or coordination between nodes, and provides a reasonable tradeoff between anonymity, usability, and efficiency. We briefly describe our experiences with an international network of more than a dozen hosts. We close with a list of open problems in anonymous communication. 1. Overview

We introduce Tarzan, a peer-to-peer anonymous network layer that provides generic IP forwarding. Unlike prior anonymizing layers, Tarzan is flexible, transparent, decentralized, and highly scalable. Tarzan achieves these properties by building anonymous IP tunnels between an open-ended set of peers. Tarzan can provide anonymity to existing applications, such as web browsing and file sharing, without change to those applications. Performance tests show that Tarzan imposes minimal overhead over a corresponding non-anonymous overlay route.

We present a design for a system of anonymous storage which resists the attempts of powerful adversaries to find or destroy any stored data. We enumerate distinct notions of anonymity for each party in the system, and suggest a way to classify anonymous systems based on the kinds of anonymity provided. Our design ensures the availability of each document for a publisher-specified lifetime. A reputation system provides server accountability by limiting the damage caused from misbehaving servers. We identify attacks and defenses against anonymous storage services, and close with a list of problems which are currently unsolved.

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Data mining can extract important knowledge from large data collections -- but sometimes these collections are split among various parties. Privacy concerns may prevent the parties from directly sharing the data, and some types of information about the data. This paper addresses secure mining of association rules over horizontally partitioned data. The methods incorporate cryptographic techniques to minimize the information shared, while adding little overhead to the mining task.

We present the traffic analysis problem and expose the most important protocols, attacks and design issues. Afterwards, we propose directions for further research. As we are mostly interested in efficient and practical Internet based protocols, most of the emphasis is placed on mix based constructions. The presentation is informal in that no complex definitions and proofs are presented, the aim being more to give a thorough introduction than to present deep new insights.

Anonymous credential systems [8, 9, 12, 24] allow anonymous yet authenticated and accountable transactions between users and service providers. As such, they represent a powerful technique for protecting users' privacy when conducting Internet transactions. In this paper, we describe the design and implementation of an anonymous credential system based on the protocols developed by [6]. The system is based on new high-level primitives and interfaces allowing for easy integration into access control systems. The prototype was realized in Java. We demonstrate its use and some deployment issues with the description of an operational demonstration scenario.

This paper presents a security of Onion Routing, an application independent infrastructure for traffic-analysis-resistant and anonymous Internet connections. It also includes an overview of the current system design, definitions of security goals and new adversary models.