Abstract: There is described a method and an apparatus which comprises a reader for reading document characteristics, circuitry permitting the formation of a message confirming the holder identity, a computer connected to said reader and message means, said computer is so designed as to be able to perform from those data obtained by the reader and said means, and possibly from other remotely-conveyed data, a mathematical processing including one or a plurality of encipherings according to a public-key cryptography method and making use therefor but of public keys, means being provided to check with said computer, by a third party, and/or remotely with another computer, the expected match between said collected data, a non-secret number independent from the document, and identification data present unscrambled on the document, which match is disclosed by the mathematical processing.