Abstract

In this work, we propose a new platform to enable service providers, such as web site operators, on the Internet to block past abusive users of anonymizing networks (for example, Tor) from further misbehaviour, without compromising their privacy, and while preserving the privacy of all of the non-abusive users. Our system provides a privacy-preserving analog of IP address banning, and is modelled after the well-known Nymble system. Nymble is a system that provides a blocking mechanism to a server to protect it from misbehaving users connecting through anonymizing networks such as Tor. Anonymous networks allow anyone to visit the public areas of the network. Here users access the Internet services through a series of routers. , this hides the user’s identities and IP address from the server. This may be an advantage for the misbehaving users to destroy popular websites. To avoid such activities, servers may try to block the misbehaving user, but it is not possible in case of anonymous networks. In such cases, if the abuser routes through an anonymizing network, administrators block all known exit nodes of anonymizing networks, denying anonymous access to misbehaving and behaving users. To overcome this problem, a nymble system is designed in which servers can blacklist the misbehaving users without compromising their anonymity. This paper explains the idea that the different service providers have different blacklisting policies. For example, Wikipedia might want to block a user one day for the first misbehaviour, one week for the second one, etc. In order to do this, we have to develop a dynamic link ability window whose length can be increased exponentially. Thus, at the start of each linkability window, all service providers must reset their blacklists and forgive all prior misbehavior.

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