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 l ), 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 l ), in order to obtain the corresponding indexed reference data (b i1 ,. .. b il ), said data being candidate data to compare to the data to be identified, said process being the steps of reading memory blocks of the databases are carried out by executing a protocol preventing the storage server from learning which memory blocks of the databases are read.