Abstract: Cloud storage is a novel data storage architecture.The security and manageability of data in cloud storage are also facing new challenges.Because users no longer store any copies of the data in their local memory,they cannot fully ensure whether the outsourced data are intact overall.How to protect the data integrity in the cloud has become a hot topic in academic research.The protocol of Provable Data Integrity (PDI) was considered to be the main method to solve this problem,this paper presented lattice-based provable data integrity for checking the integrity of the data in the cloud.The proposed scheme realizes the dynamic data verification by incorporating the idea of Ranked Merkle Hash Tree (RMHT) and lattice-based technology.The scheme realizes the fine-grained signature and reduces the computational cost required by the user to generate the authentication tag.The scheme introduces the RMHT to perform the modification verification of the data and supports the dynamic update of the data.It has strong privacy protection capability,blinds the users original data during the verification process,and the third party cannot obtain users real data information.Moreover,in order to prevent malicious third parties from launching denial-of-service attacks on cloud servers,only authorized third parties can verify the integrity of user data.Finally,security analysis and performance ana-lysis show that the proposed scheme not only has characteristics of unforgeability and privacy protection,but also greatly reduces the computational cost of signature.

Key words: Authorization checking, Cloud storage, Lattice-based cryptography, Public verification, Ranked merkle hash tree (RMHT)