Process for obtaining candidate data from a remote storage server for comparison to a data to be identified

Abstract

The invention presents a process for obtaining candidate reference data to compare to a data to be identified, implemented in a system comprising a client unit and a storage server comprising two databases, in which: —the first database comprises indexed memory blocks each comprising a corresponding encrypted indexed reference data, and —the second database comprises memory blocks indexed by all possible hash values obtained by a plurality of k indexed hash functions, and wherein each block contains a list of the indexes of the reference data which hashing by one of said hash function results in the hash value corresponding to said block, said process comprising the steps during which: —the client unit hashes the data to be identified with each of the plurality of hash functions, and reads the k memory blocks of the second database corresponding to the hash values thus obtained, the client unit identifies indexes contained in at least t out of k read memory blocks, and —the client unit reads the memory blocks of the first database indexed by the identified indexes in order to obtain the corresponding indexed reference data, said data being candidate data to compare to the data to be identified, the steps of reading memory blocks of the databases being carried out by executing a protocol preventing the storage server from learning which memory blocks of the databases are read. Another object of the invention is a system for the secure comparison of data.