1. 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 (DB 1 , DB 2 ), in which: the first database (DB 1 ) comprises a plurality of indexed memory blocks each comprising a corresponding encrypted indexed reference data (b i ), and the second database (DB 2 ) comprises memory blocks indexed by all possible hash values obtained by a plurality of k indexed hash functions (H j ), and wherein each block contains a list of the indexes of the reference data (b i ) which hashing (H j (b i )) by one of said hash function (H j ) results in the hash value corresponding to said block, said process comprising the steps during which: the client unit hashes the data (b) to be identified with each of the plurality of hash functions (H j ), and reads the k memory blocks of the second database (DB 2 ) corresponding to the hash values thus obtained, the client unit identifies indexes (i 1 ,. .. i 1 ) contained in at least t out of k read memory blocks, and the client unit reads the memory blocks of the first database (DB 1 ) indexed by the identified indexes (i 1 ,. .. i 1 ) in order to obtain the corresponding indexed reference data (b i1 ,. .. b i1 ), said data being candidate data to compare to the data to be identified, the client unit decrypts the candidate reference data and compares each of said reference data (b i1 ,. .. b i1 ) to the data (b) to be identified in order to detect a matching between the data (b) and one reference data, wherein the steps of reading memory blocks of the databases are carried out by executing an oblivious RAM protocol preventing the storage server ( 10 ) from learning which memory blocks of the databases are read.