WPES10 in real time: Jack for anonymous abuse control
4 October 2010
- Jack: Scalable Accumulator-based Nymble System by Zi Lin(University of Minnesota) and Nicholas Hopper (University of Minnesota)
The potential for abuse is a key challenge when it comes to deploying anonymity systems, and the privacy technology community has been researching solutions to this problem for a long time. Nymble systems allow administrators to blacklist anonymous accounts, without revealing or even knowing their identity.
What is the model: a user registers an account with a service, such as wikipedia. Then the user can use an anonymous channel like Tor, to do operations, like edit encyclopedia articles. This prevents identification of the author, and also bypasses a number of national firewalls that prevent users accessing the service (China for example blocks Wikipedia for some reason). If abuse it detected then the account can be blacklisted, but without revealing which one it was! The transcript of the edit operation is sufficient for preventing any further edits, but without tracing back the original account or network address of the user.
Nymble systems had some limitations. They either required trusted third parties for registration, or they were slow. A new generation of Nymble systems, including Jack, is now addressing these limitations: they use modern cryptographic accumulator constructions that have proofs of non-membership in O(1) time, to prove a hidden identity is not blacklisted. Jack can do authentication in 200ms, and opening a Nymble address in case of abuse in less than 30ms. This is getting real practical, and it is time that Wikipedia starts using this system instead of blacklisting Tor nodes out of fear of abuse.