Perm

Some users may misbehave under the cover of anonymity by, e.g., defacing webpages on Wikipedia or posting vulgar comments on YouTube. To prevent such abuse, a few anonymous credential schemes have been proposed that revoke access for misbehaving users while maintaining their anonymity such that no trusted third party (TTP) is involved in the revocation process. Recently we proposed BLACR, a TTP-free scheme that supports `reputation-based blacklisting' --- the service provider can score users' anonymous sessions (e.g., good vs. inappropriate comments) and users with insufficient reputation are denied access.