Zero-Knowledge Contingent Payments Revisited

An attack is shown that allows a buyer to learn partial information about the digital good being sold, without paying for it, and ways to fix this attack that do not require a trusted third party are presented.

Abstract

Zero Knowledge Contingent Payment (ZKCP) protocols allow fair exchange of sold goods and payments over the Bitcoin network. In this paper we point out two main shortcomings of current proposals for ZKCP, and propose ways to address them.