Research On Proxy Re-signature

Digital Signatures are widely applied in information security, identity certification, data integrity, anonymity and so on, especially significant in security of large network and electronic commerce system, and is one of the major elements in modern Cryptology fields. Digital signatures have become an indispensable security measure in computer network and an important tool in data guarantee, certification. Digital signatures are necessary in commercial, financial and military fields, and are practically applied in electronic trade, electronic check,electronic publication and intellectual property rights protection.As a new type of signature, Blaze, Bleumer and Strauss(BBS) first proposed the prototype of proxy re-signature in the year 1998. In the standard Proxy Re-Signature Scheme, a semi-trusted proxy can transform Alice's signature into Bob's signature on the same message using a re-signature key, while the proxy knows nothing about the private key of Alice and Bob, and can not sign any message on behalf of Alice or Bob.Based on the feature that the semi-trusted proxy can transform signatures between different signers, proxy re-signature scheme have very promising prospects in certificates sharing, forming weak group signatures, network path traversal proof and constructing checking system.Especially proxy re-signature scheme can be used to make a proof that some path in a graph was taken, and compared with traditional signatures in this application, it takes advantages of high efficiecy, saving space and fine security. If proxy re-signatures are combined with other tools in Cryptology, there would be a much brighter future.However since it was first proposed, proxy re-signatures haven't been attached expected emphasis, as a result of that schemes proposed so far takes a set of disadvantages and they are not suitable for most practical application. But with the virtues of BBS scheme and other proxy re-signature schemes existing, according to application circumstances, we can design more useful proxy re-signatres with less defects and more features and try to enlarge application area by means of combining with other special signature schemes. We firstly make a extensive description of proxy re-signature theories and technologies, discuss the general model and security definations, look back to the development in the last decade, study and compare and summarize the existing classic proxy re-signature schemes,and make examples for their application circumstances.Then with the feature that the semi-trusted proxy can transform signatures between different signers in proxy re-signature schemes, we discuss how to implement in common key management, path taken proof, forming weak group signatures and transparent certification, and show the great advantage of proxy re-signatures in these fields.We also improve the standard model of proxy re-signature into threshold proxy re-signature model with the idea of secret sharing. We then construct a scheme of the new model, discuss its security and list a suitable application.Finally, to make proxy re-signatures get more attention and develop faster, we point out the key problems to be resolved in the future study of proxy re-signatures.