Abstract: Anonymizing networks such as Tor allow users to access Internet services privately by using a series of routers to hide the client’s IP address from the server. The success of such networks, however, has been limited by users employing this anonymity for abusive purposes such as defacing popular websites. Website administrators routinely rely on IP-address blocking for disabling access to misbehaving users, but blocking IP address is not practical if the user routes through an anonymizing network. As a result, administrators block all known exit nodes of anonymizing networks, denying anonymous access to misbehaving and behaving users alike. To address this problem, a solution is to be implemented is called Nymble Credential System, a system in which servers can blacklist misbehaving users, thereby blocking users without compromising their anonymity. This system is agnostic to different servers’ definitions of misbehaviour- servers can blacklist users for whatever reason, and the privacy of blacklisted users is maintained.

Keywords: Privacy, Anonymity, blacklisting, misbehaving, linkability window.