## Making a Nymbler Nymble using VERBS (Extended Version). Computer Science (2010)

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Citations: | 6 - 6 self |

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@TECHREPORT{Henry10makinga,

author = {Ryan Henry and Kevin Henry and Ian Goldberg},

title = {Making a Nymbler Nymble using VERBS (Extended Version). Computer Science},

institution = {},

year = {2010}

}

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### Abstract

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 modeled after the well-known Nymble system [29,47,48]. However, while we solve the same problem as the original Nymble scheme, we eliminate the troubling situation in which users must trust their anonymity in the hands of a small number of trusted third parties. Unlike other approaches that have been considered in the literature [10,44,45,46], we avoid the use of trusted hardware devices or unrealistic assumptions about offline credential issuing authorities who are responsible for ensuring that no user is able to obtain multiple credentials. Thus, our scheme combines the strong privacy guarantees of [10,44,45,46] with a simple infrastructure as in [29,47,48]. To prevent malicious third parties from trivially colluding to reveal the identities of anonymous users we make use of a number of standard zeroknowledge proofs, and to maintain efficiency we introduce a new cryptographic technique which we call verifier efficient restricted blind signatures, or VERBS. Our approach allows users to perform all privacy-sensitive computations locally, and then prove in zero-knowledge that the computations were performed correctly in order to obtain efficiently verifiable signatures on the output — all without revealing neither the result of the computation, nor any potentially identifying information, to the signature issuing authority. Signature verification in our proposed VERBS scheme is 1–2 orders of magnitude more efficient than verification in any known restricted blind signature scheme.

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Citation Context ... users use the veil of anonymity as a license to perform mischievous deeds such as trolling forums or cyber-vandalism. For this reason, some popular websites (for example, Wikipedia [50] and Slashdot =-=[19,23]-=-) proactively ban any user connecting from a known anonymous communications network from contributing content, thus limiting freedom of expression. 2 The privacy offered by Tor is directly related to ... |

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Citation Context ...dual users without compromising their anonymity. Not only would such a system benefit the estimated hundreds of thousands of existing Tor users, but it might also be a boon to wider acceptance of Tor =-=[31]-=-. Indeed, the need for an anonymous blacklisting mechanism has been acknowledged by several key people involved with The Tor Project [20,21,31]. Thus, it is reasonable to expect that the operators of ... |