LoSt: location based storage

Abstract

For certain types of sensitive data (such as health records) it is important to know the geographic location of the file, e.g. that it is stored on servers within the USA. This is particularly important for determining applicable laws and regulations. In this paper we discuss the problem of verifying the location of files within distributed file storage systems such as the cloud. We consider a general setup for a distributed storage system and show that verifying location when such a system is fully malicious, is impossible. We then make plausible assumptions about the behavior of the system and provide a formal definition for Proofs of Location (PoL) in our setting. We show secure and efficient PoL schemes can be constructed by using a geolocation scheme and a Proof of Retrievability (PoR) scheme with a new added property that we call re-coding, which is of independent interest.