A method and system for checking a franking mark (28), comprising at least an identification code and a unique bit string, said system comprising means for: a) reading the franking mark (28), b) decoding the franking mark (28), c) checking whether the identification code is correct by comparing it to data stored in a memory (40), d) checking whether the unique bit string is valid by comparing it to data stored in said memory (40).

A security system for a transaction card having a magnetized strip, protection icon, account number, name, and expiration date displayed visually on an external portion of the card is provided. The protection icon is adjacent the account number. A personal identification number has at least three characters and is recorded on the magnetized strip along with the personal identification number, account number, name, and expiration date. The protection icon is adapted to activate a digital lock in the computerized terminal that disables any transfer of the account number, name, and expiration date if one or more characters of the personal identification number are present in the display. A processor is disposed inside the computerized terminal and is adapted to delete each of the characters of the uploaded personal identification number from the computerized terminal and each symbol from the display. A digital key enables transfer of the account number, name, and expiration date from the computerized terminal if all characters of a personal identification number have been entered on the keypad and deleted from the display. A method of using the transaction card with its security system is also provided.