Certificateless Linear Homomorphic Signature Scheme And Its Applications

With the rapid development of cloud computing and big data, cloud storage as an important service of the cloud computing has brought users unprecedented convenience and experience.However, the users may lose the control of their files while they store the files in the cloud.Therefore,the integrity and authenticity of data becomes an important security issue in cloud storage. With the continuous advancement of network technology, a variety of digital signatures have been produced in cryptography to meet different needs in different applications. Among these methods, the homomorphic signature scheme and certificateless signature have attracted more attention in cryptography. This thesis studies the formal definition, security model and design of the certificateless homomorphic signature as well as its application in the public verification of the file integrity in cloud storage.In this thesis, we first review the formal definition and security model of two commonly adopted signature schemes, i.e. the homomorphic signature and certificateless signature.Based on the nature of the concepts and methodologies introduced in these two schemes, we propose the formal definition and security model of the certificateless homomorphic signature by combining the homomorphic signature and the certificateless public key cryptosystem. To the best of the author's knowledge, such design scheme is proposed for the first time and has not been reported in literature before.Based on the linear homomorphic signature scheme proposed by Boneh et al., we develop two practical certificateless linear homomorphic signature schemes, CLLHS ? and CLLHS ?, using the bilinear mapping. In the first scheme, we eliminate the drawbacks ofvector length increase in Boneh's method. Then, we prove that our scheme can achieve the existential unforgeability against adaptive chosen identity and adaptive chosen-dataset attack in the random oracle model. In the second scheme, a dataset tag of homomorphic signature is generated using a secure certificateless signature scheme. The signature of the message vector is also produced by borrowing the BLS short signature idea. Compared with CLLHS?, the modification made in CLLHS ? results in reduction of the exponential operation of the multiplicative group in its signature and verification algorithms. Moreover, we analyze the computational cost of the above two certificateless linear homomorphic signature schemes from a theoretical point of view. The correctness and efficiency of the two proposed schemes are verified by simulation experiments. The results show that CLLHS ? has higher operating efficiency in practical use.Finally, we propose the solution to the public verification of integrity of user's file in the cloud storage based on CLLHS ?. This solution enables the users to realize the public verification of file integrity efficiently and with ease.In this thesis, we design two certificateless linear homomorphic signature schemes and apply them to the integrity verification of user's file in cloud storage. This novel design concept can further improve the efficiency and safety of the public verification of data integrity in cloud storage. It is of great significance in theory and in practice to adopt thecertificateless linear homomorphic signatures for improving cyberspace security and promoting the efficiency and security of cloud storage.