Public Integrity Auditing of Shared Encrypted Data within Cloud Storage Group

The pandemic of COVID-19 has posed a severe challenge to the traditional on-site centralized development projects; people therefore have to share data in a group by the cloud storage server and develop projects at home. The cloud server is untrustworthy, although it supplies the powerful computing capability and abundant storage space; so far wide research has been proposed to verify data integrity. Therefore, how to leverage the cloud server and ensure the integrity of the data (especially the encrypted data) stored on the remote cloud devices remains an issue for the clients. To address this issue, we utilize the technique of homomorphic hash function to implement reencryption ciphertext blocks and introduce a certificateless signature scheme for the integrity verification of encrypted data shared within a group. A detailed challenge-and-response game represents that the proposed scheme can preserve encrypted data blocks integrity against the internal/external attacker and malicious cloud service servers. We give the theoretical and experimental performance analysis of the scheme and exhibit that the scheme is efficient and practical.