Publication Information
S. R. Tate and R. Vishwanathan. Improving Cut-and-Choose in Verifiable Encryption and Fair Exchange Protocols using Trusted Computing Technology, in Proceedings of the 23rd Annual IFIP WG 11.3 Working Conference on Data and Application Security, 2009, pp. 252-267. Security&CryptographyConference
Abstract
At the heart of many fair exchange problems is verifiable escrow: a sender encrypts some value using the public key of a trusted party (called the recovery agent), and then must convince the receiver of the ciphertext that the corresponding plaintext satisfies some property (e.g., it contains the sender’s signature on a contract). Previous solutions to this problem are interactive, and often rely on communication-intensive cut-and-choose zero-knowledge proofs. In this paper, we provide a solution that uses generic trusted hardware to create an efficient, non-interactive verifiable escrow scheme. Our solution allows the protocol to use a set of recovery agents with a threshold access structure, the \emph{verifiable group escrow} notion which was informally introduced by Camenisch and Damgard and which is formalized here. Finally, this paper shows how this new non-interactive verifiable escrow scheme can be used to create an efficient optimistic protocol for fair exchange of signatures.