Reliable Evidence of Data Integrity from an Untrusted Storage Service

Digital storage demand is growing with the increasing use of digital artifacts from media files to business documents. Regulatory frameworks ask for unaltered, durable storage of business communications. In this paper we consider the problem of getting reliable evidence of the integrity and existence of some data from a storage service even if the data is not available for reference anymore and even if the partner may be untrustworthy or malicious. Several solutions are presented, among them the first cryptographically secure approach providing evidence of the integrity of remotely stored data, without owning or transferring the complete original data.