A Traceable and Pseudonymous P2P Information Distribution System

Anyone can publish various kinds of information on the Internet almost freely, but in some cases such information distribution is inhibited by the authorities. In order to resist such censorship, there have been developed many anonymous information distribution systems such as Free net and Tor, but some people argue that such a system may also be a hotbed of crime since scrupulous anonymity disturbs investigations. In this paper, an article distribution system is proposed, which protects pseudonymity of users from surveillance by the authorities as with existing anticensorship systems. As a novel point, the proposed system allows a user to trace the publisher of an article by cooperation of the users who have relayed the article. This will suppress criminal acts abusing pseudonymity in the system. On the other hand, it is difficult to trace the publisher for a single government or an organization alone unless it obtains cooperation of multiple users. The proposed system will therefore be able to avoid authoritarian censorship or surveillance by the authorities. The system adopts P2P architecture, and a user can publish articles to other users like Netnews. A published article is relayed by node to node and spreads over the network of the system. In order to trace the publisher of an article, a user records a relaying log when he relays an article. A relaying log contains information about the predecessor from whom the user received the article. A user can trace the publisher by gathering relaying logs. Each user has responsibility to determine whether to disclose a relaying log or not, considering the content of the article. If all users along the path from the publisher agree to cooperate in gathering their logs, they will be able to trace to the publisher. The performance of the system is discussed in evaluation, how users' actions affect traceability, and what should users do if governments intervene in the system.