Security Analysis of AN.ON's Payment Scheme

摘要

In recent years several payment schemes have emerged for anonymous communication systems such as AN.ON and Tor. In this paper we briefly present a payment scheme that is deployed and currently used by AN.ON. The main contribution of this paper is a security analysis of the most important cryptographic protocols involved in the payment process. The analysis of the protocols shows that they contain several weaknesses that need to be addressed to provide a fair service. We show how an attacker can use the weaknesses to surf on other's credits. Finally, we propose a fix for the protocols in order to withstand the encountered attacks.