The process consists of carrying out the first phase of generating the transaction signature (9), with prior authentication by the cardholder, in the issuing centre (3) through its authentication server (5), a second phase of decimalising (10) the signature (9) to obtain a valid permutation number and a third phase of permuting (11) the intermediary positions or digits of the card, the processor fixing a BIN and maintaining the check digit. In this way, the digits forming the expiry date are permuted. The card and expiry date are sent in the data flow (12) of the transaction to the acquiring server (7), from where they are sent back to the issuing centre (3), to its processing centre (6) to be specific, where three other operative phases are carried out: the new generation of the signature (13), its decimalisation (14) and lastly the inverse process (15) to reestablish the card's real data and expiry date.