## Cryptology ePrint Archive: Report 2004/373

Delegateable Signature Using Witness Indistinguishable and Witness Hiding Proofs

Chunming Tang and Dingyi Pei and Zhuojun Liu

Abstract: A delegateable signature scheme is a signature scheme where the owner of the signing key(Alice) can securely delegate to another party(Bob) the ability to sign on Alice's behalf on a restricted subset $S$ of the message space. Barak first defined and constructed this signature scheme using non-interactive zero-knowledge proof of knowledge(NIZKPK)\cite{Barak}. In his delegateable signature scheme, the function of NIZKPK is to prevent the signing verifier from tell which witness(i.e. restricted subset) is being used.

Witness indistinguishable(WI) and witness hiding(WH) proof systems are weaker proof model than zero-knowledge proof and were proposed by Feige and Shamir in \cite{FS}, however, the verifier cannot also distinguish the witness which is being used in these two protocols. In this paper, we construct delegateable signature scheme using WI and WH proof protocols.

Category / Keywords: cryptographic protocols / Digital signature, delegateable signature,zero-knowledge proof system, witness indistinguishable proof,witness hiding proof