Research On Associated Deletion Technology For Multi-copy In Cloud And Its Applications

With the rapid development of Internet technologies,the total scale of global data grows explosively.At the meantime,the data of user is also getting more and more massive.Such data brings heavy local storage and management overhead to users.The contradiction between continuous growth of data and limited local storage resources and low computing power restricts the users.But the emergence and development of cloud computing and cloud storage provides a new way to solve this difficult problem.More and more users choose to outsource their own data to the cloud to reduce the overhead.Although cloud storage brings convenience to users,it also increases the risk of data security incidents.Firstly,the ownership and the management of outsourced data are separated.Users can only guarantee data confidentiality through encrypting them before outsourcing,but this will introduce the burden on the management of data keys for users.Secondly,due to natural disasters or uncertain faults of cloud storage devices,users need to back up own data for multiple copies to increase availability at the cost of increasing the risk of data leakage.Finally,after the multiple copies of outsourced data are stored,users also need to ask the cloud service provider to perform assured associated deletion for all the backups of the data in cloud,which can ensure that the cloud service provider can not disclose or illegally use the users data.Therefore,how to provide users with a low-cost,high-availability,provable and accountable deletion scheme for the outsourced data is an urgent problem to be solved.Most of the existing deletion schemes have large computational overhead,and do not provide multi-copy associated deletion or effective evidence of deletion operation.In this dissertation,the research hotspots given above are deeply explored,and our main work and contributions are summarized as follows:(1)We propose a multi-copy verifiable associated deletion scheme for outsourced data,and it is also a completely full-cycle management scheme for users data in cloud.The scheme has the following advantages: First,the scheme utilizes the address-based multi-copy associated method of cloud data,and the multi-copy storage improves the availability of the outsourced data;Besides,the scheme applies symmetric and asymmetric cryptographic algorithms to ensure the confidentiality of the data,and at the meanwhile our scheme uses a simple deformation of the RSA blind signature algorithm to make the encrypted keys of data outsourced securely,which also reduces the burden of users on the management of a large number of keys.In addition,our scheme proposes the concept of pre-deleting sequence,which is a sequence to control the order of the deletion operation and generation of evidence for the copies specified by users,and then we combined it with the Merkle hash tree to create an innovative rule,which can make cloud service providers provide users with verifiable deletion evidences;Last but not least,we use blockchain to permanently store all the deletion evidences in the network ledger,in which the data can be publicly verified,undeniable and non-tampering,so that users are provided with an accountable deletion solution for the outsourced data.(2)According to the theoretical deletion scheme proposed in this dissertation,we further design and implement a blockchain-based verifiable deletion cloud disk system,which can also verify the feasibility and correctness of our scheme from the perspective of practical application.In the Linux environment,we use the Django framework of Python to deploy our B/S based system.In addition to the basic functions such as login and registration,our system mainly provide users with encrypting and uploading,decrypting and downloading,verifiable deleting,verifying for evidence and rights protecting.At the same time,our cloud disk system uses the Geth,Ethereum client,to build a private Ethereum blockchain network,which simulates the process of recording and tracking the deletion evidence in the public blockchain.