Studies On Universally Composable Digital Signature And Its Key Problems

Along with the development of computer and network technologies, digital signaturehas been widely used in people's daily lives. Lots of international experts and scientistsfocus on the studies of digital signature's theories, technologies, and applications. UniversalComposablity (UC) framework getting more and more attention dues to it can simplify theanalysis of protocols and provide more powerful security. As we know, the researches ondigital signature under the UC framework are very rare. Moreover, many digital signatureschemes are without reasonable assumptions of the definitions of ideal functionality, andsome protocols lack the analysis under the UC framework. This paper involves our studiesand designs of threshold signature, proxy re-signature and proxy signature under the UCframework. Our contributions are shown as follows:1. The current researches on threshold signature under the UC framework are far fromenough, and the ideal functionality is imperfect. Therefore, the studies of UC securethreshold signature schemes have significant values. We provide a more precise defini-tion of the ideal functionality for threshold signature primitive, and reconstruct a seriesof protocols, including two threshold signature protocols and two proactive thresholdprotocols, which are secure under UC Framework. The proposed protocols are notonly provably secure, but also secure under the UC framework. Our works comple-ment the shortage of the former researches, and better the researches on the formalstudies of the UC-based secure models for the threshold signature primitive.2. Proxy re-cryptography is one of the fresh topics in modern cryptography. As far aswe know, there is no UC secure proxy re-signature scheme. We first introduce the UCframework to the studies of proxy re-signature, and propose two efficient proxy re-signature schemes with the UC security. We not only further perfect the game-basedsecure model for the proxy re-signature primitive, but also give its UC-based securemodel for the first time. Our works pave the way for the future works on studying theUC secure proxy re-signature protocols. 3. There is little work on UC secure proxy signature nowadays. We extend the UC Frame-work to the proxy signature scenarios, and propose two UC secure proxy thresholdsignature protocols. Furthermore, we design the multi-times proxy signature schemeand key-insulated proxy signature scheme which are suitable for mobile agent system.These schemes are provably secure under random oracle model, and efficiently solvethe abuse of mobile agent and key exposure problem. Our works formalize the securemodel for the proxy signature primitive, which lays foundation of future works.