Method of authentication by a NFC reader of an electronic tag fitted to a product , the product having an identifier ( ID P ), the tag comprising a memory containing, from manufacture, a unique tag identifier ( UID ) recorded moreover in a database , the method being characterized in that at least one security key ( K ) has been generated on the basis of the application of a hash function ( H ) to the unique identifier ( UID ) of the tag modified by a transformation function ( T 1 ) having as parameter at least one value ( Salt ) associated with the product , the said at least one security key ( K ) being recorded in the database , a hashed product code ( C p ) associated with the product , having been generated on the basis of the application of a hash function ( H ) to the identifier ( ID P ) of the product modified by a transformation function ( T 2 ) having as parameter at least the same value ( Salt ) associated with the product and used to generate the said at least one security key ( K ), the transformation functions ( T 1 ) and ( T 2 ) being identical, the hashed product code ( C p ) having been recorded in the memory of the tag and in the database , and being accessible during an interrogation of the tag by the reader by virtue of the said at least one security key ( K ), and in that : - the reader interrogates the tag to read the unique identifier (UID) of the latter, - the reader transmits the unique identifier (UID) of the tag to the database , - if the unique identifier (UID) of the tag is recorded in the database , the reader receives from the latter the said at least one security key ( K ) associated with the unique identifier (UID) of the tag , - the reader dispatches a reading request to the tag by virtue of the said at least one security key ( K ) received from the database , - in case of positive response of the tag , the reader reads, by virtue of the said at least one security key ( K ), the hashed product code ( C p ), - the reader dispatches a request to the database to verify whether the hashed product code ( C p ) transmitted by the tag corresponds to the hashed product code associated with the tag and recorded in the database , and - in case of correspondence, the reader receives from the database an information item ( I a ) confirming the authenticity of the product . - the reader interrogates the tag to read the unique identifier (UID) of the latter, - the reader transmits the unique identifier (UID) of the tag to the database , - if the unique identifier (UID) of the tag is recorded in the database , the reader receives from the latter the said at least one security key ( K ) associated with the unique identifier (UID) of the tag , - the reader dispatches a reading request to the tag by virtue of the said at least one security key ( K ) received from the database , - in case of positive response of the tag , the reader reads, by virtue of the said at least one security key ( K ), the hashed product code ( C p ), - the reader dispatches a request to the database to verify whether the hashed product code ( C p ) transmitted by the tag corresponds to the hashed product code associated with the tag and recorded in the database , and - in case of correspondence, the reader receives from the database an information item ( I a ) confirming the authenticity of the product . <EOS>