Design And Implementation Of Cloud Storage Integrity Verification System Based On Certificateless Linear Homomorphic Signature

Cloud computing is a new computing model which emphasizes resource rent and application hosting,etc.Cloud storage is a familiar service supplied by cloud computing.In cloud storage,a user saves his/her data by renting some storage space in the cloud.After that,he/she can access and manage his/her data in the cloud at any time and in any place through the internet.With the continuous development of cloud storage,serious challenges have occurred with respect to data security in cloud storage.Among which data integrity attracts a lot of attention.How to detect whether one's data have been tampered or damaged in the cloud has become one of the research hotspot in the area of data security in cloud storage.Cryptography can provide solutions for data integrity in cloud storage.This thesis mainly studies the techniques of public verification of data integrity in cloud storage based on linearly homomorphic signatures.At first,this thesis designs a new certificateless linearly homomorphic signature scheme on the foundation of the certificateless short signature scheme by MiaomiaoTian et al.and the homomorphic signature scheme by Boneh D et al..The scheme gets rid of public key certificate in traditional public key cryptosystems,and at the same time solves the key escrow problem in identity based cryptosystems.And the signing algorithm possesses homomorphic property for linear operations of vectors in a subspace.We analyze the performance efficiency of the scheme and demonstrate its existential unforgeability under adaptive chosen subspace attacks.Next,the designed certificateless linear homomorphic signature scheme is implemented.Taking into account the core operation is the bilinear pairing on the elliptic curves,we choose to use JAVA programming language to set up the key generation center KGC for a certificateless cryptosystem.After initialization system parameters of KGC,we realize the partial private key extract,user key generation,sign,signature derive and verification algorithms of the certificateless linearly homomorphic signature scheme.The results of the experiments indicate that the scheme has a relatively short key length and signature length,and the computation time of sign and verification is also short.Finally,a data integrity public verification system for cloud storage is designed and implemented.The system employs our certificateless linearly homomorphic signature scheme as a main building block.In the system,the key generation center KGC of certificateless cryptography is deployed in the cloud storage server.The system possesses the functionality of uploading files by a user and public verifying of file integrity in cloud storage.The experiments simulate uploading,downloading,deleting files,as well as data integrity checking by multiple users using the system.The analysis of experimental results demonstrates that the system runs stably and reliably.Also,the system enjoys the advantages of short data tags,short integrity checking time,and convenience and flexibility in deployment.