LH*RE: A Scalable Distributed Data Structure with Recoverable Encryption

Abstract

LH*RE is a new Scalable Distributed Data Structure (SDDS) for hash files stored in a cloud. The client-side symmetric encryption protects the data against the server-side disclosure. The encryption key(s) at the client are backed up in the file. The client may recover/ revoke any keys lost or stolen from its node. A trusted official can also do it on behalf of the client or of an authority, e.g., to imperatively access the data of a client missing or disabled. In contrast, with high assurance, e.g., 99%, the attacker of the cloud should not usually disclose any data, even if the intrusion succeeds over dozens or possibly thousands of servers for a larger file. Storage and primary key-based access performance of LH*RE should be about those of the well-known LH* SDDS. Two messages should typically suffice for a key-based search and four in the worst case, with the application data load factor of 70%, regardless of the file scale up. These features are among most efficient for a hash SDDS. LH*RE should be attractive with respect to the competition.