METHOD FOR TESTING IF A DATA ELEMENT BELONGS TO A LIST OF REFERENCE DATA ELEMENTS

摘要

The present invention relates to a method for testing if a data element (x'), called candidate data element, belongs to a list of reference data elements (xi), performed by a client device (102) and comprising the steps of : - generating (SC1) an encrypted candidate data element (y') by encrypting said candidate data element (x') with a leveled fully homomorphic DGHV (Dijik, Gentry, Halevi, Vaikuntanathan) encryption scheme, - transmitting (SC2) said encrypted candidate data element (y') to a server device (103) storing said reference data elements (xi) encrypted with said leveled fully homomorphic DGHV encryption scheme, called encrypted reference data elements (yi), - receiving (SC3), from said server device (103), a delta value depending on a product of differences between said encrypted candidate data element (y') and each of said encrypted reference data elements (yi) - decrypting (SC4) said delta value with said leveled fully homomorphic DGHV encryption scheme, - based on said decrypted delta value, determining (SC5) whether said candidate data element (x') belongs to said list of reference data elements (xi), said leveled fully homomorphic DGHV encryption scheme being such that a ciphertext yi of a data xi in [0; n[, i,n being integers, FHE (Fully homomorphic Encryption) encrypted with a FHE secret key p, is equal to qi.p + n.ri + xi where qi and ri are random integers, and such that the ciphertext yi is decrypted by computing xi=(yi mod p) mod n.