| Abstract [eng] |
Ring signature is cryptografic primitive, that enables a user to sign a message anonymously on behalf of a certain group of people, which includes the signer and it is called a ring. From 2001, when Ring Signature was first invented by Rivest, Shamir and Tauman, massive interest has been shown to ring signcryption algorythms and diferent schemes were introduced. The goal of this work is to find out, whether the ring signatures work well in forums. Suppose, there is a signer who wants to stay anonymous, and there are several group members who would like to identify the signer. In this paper it is shown, that at least one ring signature scheme is created where the signer can be revealed if at least three of the members in the ring start to cooperate with each other, and the whole attack on that particular scheme is described. After it is proven that a particular ring signature is insecure, comparisons to a very similar ring signature scheme are made, and recommendations are given on what should be improved so that this attack will not reveal the identity of the signer. |
