Study On Authorization Auditing And Privacy Retrieval In Cloud Storage

Cloud storage is based on cloud computing technology,taking the pay-as-you-go service method to provide users with powerful computing resources and unlimited storage space.Users only need to use lightweight devices to connect to the network,and they can access outsourced data anytime and anywhere,without spending a lot of money on the maintenance of local hardware and software systems.While cloud storage brings convenience to users,it also brings many security risks.First,due to the incomplete trustworthiness of the cloud server,users need to authorize auditors to help them periodically check the integrity of the data stored in the cloud.When an auditor is unavailable or misbehaves,the user needs to revoke the auditor and reauthorize a new auditor.In order to safely update the authorized auditor,the existing authorization audit schemes require the user to download all the data blocks to the local devices,update the data tags with the auditor’s authorization information,and then upload them to the cloud server for storage.Due to the large amount of data shared in the cloud,this will cause users to spend a lot of computational overhead and communication overhead.Therefore,how to securely and efficiently authorize and update auditors is an urgent problem to be solved.Second,cloud storage data often contains a large number of sensitive data sets for users.The cloud server can infer various private information of the user through the user’s retrieval records.Although the existing private information retrieval schemes can ensure the privacy of the user’s query data information,it is assumed that the cloud server will honestly perform all the private information retrieval.Cloud servers may only perform partial information retrieval for reasons such as self-interest,software,and hardware failures.Then return incomplete and incorrect retrieval results to users.So how to achieve verifiable private information retrieval in cloud storage is another challenge.In this dissertation,we focus on challenging issues in cloud storage authorization auditing and private information retrieval.The main contributions of our works can be summarized as follows:(1)We make the first attempt to formally address the problem that how to update an authorized auditor in cloud storage without requiring recalculating the entire data tags.By introducing a new cryptographic primitive-chameleon vector commitment(CVC),we propose a new authorization auditing scheme in cloud storage.The scheme makes the communication overhead of updating data tags independent of the number of tags,with a constant size.At the same time,the cloud server performs the update operation on data tags,which reduces the computational overhead of the user.Compared with the existing solutions,the proposed scheme can not only ensure the security of authorization auditing but also efficiently update authorized auditors,which is more suitable for cloud storage authorization auditing scenarios.(2)We further study the problem of verifiable private information retrieval in cloud storage.Based on the cryptographic primitive of the chameleon vector commitment,using offline/online servers,we propose a verifiable private information retrieval scheme.The scheme can simultaneously achieve both private information retrieval and retrieval result verification.The use of offline/online servers reduces the computational,communication,and storage overhead between users and servers in the process of private information retrieval,thereby improving the efficiency of private information retrieval.Finally,based on the cryptographic primitives of the vector commitment(VC),the user can verify the retrieval results,which ensures the correctness and integrity of the retrieval data.