Provably secure and efficient proxy signature with untrustworthy proxy signer

Proxy signature has drawn great concerns.However, there still remains a challenge to construct a provably secure and effcient proxy signature scheme.In this paper, we propose an effcient proxy signature scheme based on factoring, and prove that it is secure in the random oracle.Furthermore, we present a new type of proxy signature, called Proxy Signature with Untrustworthy Proxy Signer, and construct a concrete scheme.     

The Braid-Based Bit Commitment Protocol

Introduction Theprimitiveofbitcommitmentcanbeim-plicitlytracedbacktoveryearlyworksbyRa-bin[1],Blum[2],andShamiretal[3].Itsbasicsce-nariois:AlicecansendaprooftoBobthatcom-mitshertoabitb(0or1)ofherchoiceinsucha waythatBobcannottellwhatbis(commit phase),butlaterAlicecanopenthecommitment andprovehimwhatboriginallywas(openphase).Abitcommitmentschemeissaidtobebindingif thepromisee(Alice)hasnochancetocheat,i.e.,shecannotopentheoppositeofheroriginalcom-mitment.Wecallabitcommitmenthidingifthe commi…