Deploying Low-Latency Anonymity: Design Challenges and Social Factors

摘要

Anonymous communication systems hide conversations against unwanted observations. Deploying an anonymous communications infrastructure presents surprises unlike those found in other types of systems. For example, given that users shouldn't need to trust each other or any part of the system, no single authority or organization should be able to observe complete traffic information for anyone's communication. This makes commercialization difficult and requires a rethinking of incentives for both users and infrastructure participants' in no small part because a user's security depends directly on the infrastructure's size and the number of other system users. To address these and related issues, we designed Tor (the onion routing), a widely used low-latency, general-purpose anonymous communication infrastructure' an overlay network for anonymizing TCP streams over the real-world Internet. (1) Tor requires no special privileges or kernel modifications, needs little synchronization or coordination between nodes, and provides a reasonable trade- off between anonymity, usability, and efficiency. Since deployment in October 2003, the public Tor network has grown to about a thousand volunteer-operated nodes worldwide and traffic averaging more than 110 Mbytes per second from hundreds of thousands of concurrent users, ranging from ordinary citizens concerned about their privacy to law enforcement and government intelligence agencies looking to operate on the Internet without being noticed and corporations that don't want to reveal information to their competitors. This article discusses how to use Tor, who uses it, how it works, why we designed it the way we did, and why that design makes it usable and stable. I. Distributed trust and usability The US Naval Research Laboratory and the Free Haven Project researched, developed, and deployed Tor, the third generation of deployed onion- routing designs, 1--3 under US Office of Naval Research (ONR) and DARPA funding to secure gove.