Local anonymity in the internet

Packet-switched computer networks of all sizes are widely used for personal, professional, and governmental communication. However, the speed, versatility, and largely unregulated nature of computer networks coupled with the availability of affordable high-capacity storage makes it possible and even practical to routinely maintain detailed logs of communication without indication to the communication partners. Although the contents of messages can be protected by cryptography, the simple fact that the network carries an encrypted message from one party to another is a piece of intelligence not as easily protected. For example, the message's destination must be revealed at some level so the network can deliver it. In this two-part dissertation we investigate techniques for protecting the identities of communication partners from worst-case adversaries such as the network infrastructure itself, including routers, switches, and hubs. In the first part, we survey and compare the nature of the untraceability offered by anonymity protocols described in the literature. We then introduce local anonymity as a new model of network anonymity that complements the protection afforded by existing network privacy schemes. In the second part, we describe the experimental implementation of two protocols using local anonymity techniques and compare their performance We find that while both protocols achieve satisfactory performance, superposed sending (also known as a DC network) offers better performance and security tradeoffs in most applications than the simpler and more obvious alternative.