Comments on "Efficient Public Verification of Data Integrity for Cloud Storage Systems From Indistinguishability Obfuscation"

Recently, Zhang et al. proposed a novel public data integrity verification scheme for the cloud storage using indistinguishability obfuscation (iO), and extend it to support batch verification and data dynamic operations (IEEE Transactions on Information Forensics and Security, vol. 12, no. 3, pp. 676-688, Mar. 2017). However, we find that the scheme has two flaws: (a) the self-checking of the uploaded blocks and tags in Store phase is not reliable, i.e., it is easy to generate invalid block-tag pairs without being detected; (b) the extended scheme for data dynamic operations suffers from a chosen message attack, i.e., if some uploaded blocks match a certain pattern, the cloud storage is able to replace any existing block by a forged one without being detected, which violates the scheme's security model. Then, we provide solutions to these problems while preserving all the desirable features of the original scheme.