Message-locked Encryption with File Update
Message-locked encryption (MLE) (formalized by Bellare et al. [5]) is an important cryptographic primitive that supports deduplication in the cloud. Updatable block-level message-locked encryption (UMLE) (formalized by Zhao and Chow [13]) adds the update functionality to the MLE. In this paper, we formalize and extensively study a new cryptographic primitive file-updatable message-locked encryption (FMLE). FMLE can be viewed as a generalization of the UMLE, in the sense that unlike the latter, the former does not require the existence of BL-MLE (block-level message-locked encryption). FMLE allows more flexibility and efficient methods for updating the ciphertext and tag.