Secure Cloud Storage With Blockchain Techniques

Due to the rapid growth of data on the Internet,cloud storage service providers have to use deduplication techniques to reduce duplicate data and save their disc space.However,duplicate check in conventional deduplication schemes cannot recognize the randomized ciphertext,which is generated by common cryptography algorithms.In order to solve this problem,previous works proposed secure deduplication schemes to provide deduplicatable cloud storage by utilizing verifiable encryption or introducing third party verification.However,the existing works only consider the protection of confidentiality or the minimization of duplicate ratio.Most of them do not consider the low reliability of their centralized storage architectures and the threats brought by i mplementing third parties.In this case,how to construct a reliable and secure deduplication scheme and eliminate the third party has become a challenge.This thesis proposes a secure and reliable cloud storage deduplication scheme for the data reliability.Threats model and security goals are proposed based on the typical attacks in cloud storage systems.To achieve these goals,this thesis proposes a security concerned distributed deduplication scheme.In this scheme,the original data is encrypted by a verifiable cryptography algorithm before the duplicate check.Then the cloud storage service providers implement client side deduplication based on the fingerprint of the ciphertext.Data blocks are distributed to multiple servers by a RAMP secret sharing scheme for the improved reliability if they have no duplicate copy on the cloud servers.A third party is introduced to provide confidentiality for verifiable encryption algorithm.With the help of Lagrange Interpolation Polynomial,data owners can recover their data without accessing all the outsource data blocks.This thesis proposes a blockchain based data storage scheme for the introduced third party.Meta data is recorded on blockchain to ensure that data owner can recover their data even when the local data lost.The randomization of encryption and signature is provided by the random number used in the consensus mechanism.In this way,the third party for verification is eliminated and the collusion between the third party and cloud servers will not exist.Besides,this thesis constructs a payment protocol based on smart contract.Incentive mechanism and the proof of retrievability encourage the cloud server to provide better storage service.Finally,the process of data storage is recorded on blockchai n and the data owner performs local duplicate check by blockchain data.As a result,the possibility of side channel attack is reduced.This thesis analyzes the proposed scheme theoretically,and it also demonstrates that the proposed scheme meets the requirements of confidentiality,integrity,and availability.Meanwhile,the reliability and security of the blockchain based cloud storage scheme is also demonstrated.Finally,the simulation shows the performance of secret sharing scheme under different parameters.The comparisons show that the proposed scheme can provide higher level of security protection than the original scheme with nearly the same time consumption.Besides,the proposed scheme spends 90% less time than a previous work on the same data.