Research On Proxy Re-signature With Special Properties

Proxy re-signature is a cryptographic research hotspot in recent years and iswidely used in many fields, such as cloud storage, authentication, rights managementand so on.We firstly look back to the development of proxy re-signature, introduce basictheories and key technologies, discuss the general model and security definitions,compare and summarize the existing classic proxy re-signature schemes.Most existing proxy re-signature schemes are existential unforgeability, where anadversary will be able to forge a signature on a new message rather than on a messagethat has already been signed. However, Strong unforgeability can protect the existingmessage-signature pairs from being forged. By using TCR hash function, abidirectional proxy re-signature scheme is proposed. Based on collision-resistanttarget collision resistant（TCR） hash function and computational Diffie-Hellmanassumption, the proposed scheme is proved to be strongly unforgeable under adaptivechosen message attacks. The results show that the proposed scheme in computationalefficiency is superior to the available proxy re-signature schemes with strongunforgeability. Compared with these schemes, the new scheme has short systemparameters, short signature, short re-signature and more security properties.The most existing threshold proxy re-signature shemes have one threshold value.In many practical applications, the number of proxies is often dependent on thesignificance of the message to be re-signed, which requires the threshold value to bechangeable. Based on the Ateniese et al’s proxy re-signature scheme Sbiand theChinese Remainder Theorem, a flexible threshold proxy re-signature schemes isproposed in this paper, and its security is proved. According to the changeablethreshold value, each proxy can locally produce his re-signature key share and thecorresponding verification key. The lengths of public parameters and signature of theproposed scheme are shorter those of previously schemes. Compared with otherexisting schemes, this scheme can provide better efficiency in terms of thecommunication and computation cost. Finally, we study proxy re-signature scheme applications, discusses thechallenging problems to be resolved in the future study of proxy re-signatures.