Efficient Identity-Based Provable Multi-Copy Data Possession in Multi-Cloud Storage, Revisited

Storing multi-copy of data file on multi-cloud may be useful in some practical contexts. How to ensure the integrity of a user's multi-copy becomes very important in this case. In recent work, Li et al. proposed an efficient "identity-based" auditing protocol (LYZ-protocol, for short) to achieve this goal. The "identity-based" property guarantees that the resulting primitive does not rely on PKI to manage certificates. However, in this letter, we note that the performances of this protocol can be further improved. More precisely, by introducing a new hash function modeled as a random oracle, the communication costs of original LYZ-protocol can be greatly reduced. In addition, the building block of a traditional signature scheme used in this protocol results in the entire protocol not being completely identity-based, and thus it may still bear the burden of managing certificates. Therefore, by replacing this signature with an identity-based scheme, we can obtain a completely identity-based protocol. Finally, the performance analysis shows that the modified LYZ-protocol outperforms the original one.