Certificate-based Linearly Homomorphic Signature And It's Applications In The Cloud Storage

With the constant development of computer technology and Internet today,we have entered the era of big data.Cloud storage technology provides a very important service for users to save and manage their files.However,because the cloud storage environment is provided by the cloud storage provider,when the users upload their files to the cloud,they also lost the absolute control of their files.Therefore,how to guarantee the integrity,authenticity and non-repudiation of files in the cloud storage environment is still a very significant research issue.With the development of the cryptography in the new technology of the Internet,various types of digital signature have come into being which can meet different needs in different situations as a large category.Among them,homomorphic signature,especially linearly homomorphic signature schemes under various public key cryptosystems have become a hot research focus in the field of cryptography.Based on the study of certificate-based public key cryptosystems and linearly homomorphic signature schemes,this thesis presents a certificate-based linearly homomorphic signature schemes,and then employs it to design and implement a file integrity verification system for cloud storage.In this thesis,at first,we review the linearly homomorphic signature and BLS short signature scheme.By making use of some research methods from related literature,we combine the characteristics of linearly homomorphic signature with certificate-based public key cryptosystems to put forth the formal definition and security model of certificate-based linearly homomorphic signatures schemes for the first time.Then using the main idea of Boneh D et al.'s the linearly homomorphic signature scheme for reference,we propose a certificate-based linearly homomorphic signature scheme CB-LHS.In the scheme,the vectors in a base of a subspace is signed using a technique similar to that of BLS short signature scheme.Meanwhile,we have not only analyzed the security of the scheme-the signature is existentially unforgeable under adaptively chosen subspace attacks,but also carried out detailed performance analysis of the scheme.Finally,this thesis designs and implements a file integrity verification system for cloud storage based on the proposed linearly homomorphic signature scheme CB-LHS.Through the system,it is reassuring for the users in the system to upload their files to the cloud server since the signing and verification process is convenient,and greatly reduced the computational cost and communication overhead for the integrity checking of the files.Our file integrity verification system for cloud storage effectively prevents the attackers with malicious purpose from tampering or forging a user's files.In addition,this thesis also conducts a large number of experiments in Windows system.The time cost of the algorithms of certificate generation,signature generation,signature derivation and signature verification is counted.Meanwhile,the experimental results of the file integrity verification system for cloud storage are also analyzed.The experimental results and corresponding analysis demonstrate that the proposed certificate based linearly homomorphic signature scheme and the file integrity verification system for cloud storage are stable,secure and efficient.