On the unforgeability of the Chaum — Pedersen blind signature scheme

The paper is devoted to the analysis of the unforgeability property of the Chaum — Pedersen blind signature scheme in case an adversary is able to initiate parallel sessions of the signature generation protocol. It is shown that the scheme does not ensure strong unforgeability, i.e., it allows to create the forgeries for “old” messages that were legitimately signed. An analysis of the weak unforgeability property (the adversary's task is to create a forgery for a new message) is also conducted. Using the reduction method, we obtain a security bound on the weak unforgeability property in the algebraic group model and random oracle model. This estimation identifies the base problems whose complexity underpins the scheme security.