Importance

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Abstract

A method and apparatus for verifying that the bearer of a card (e.g., credit card, bank card, etc.) is authorized to use the card. The card bears machine-readable indicia of an account number (PAN) and the bearer of the card has memorized a personal identification number (PIN). There is associated with the PAN a check number (PCN) which is derived by (1) generating a first cipher Y1 by encrypting the PAN using the PIN in combination with a secret security number as a key, the bits of which address a data encryption process; (2) generating a second cipher by decrypting the first cipher using the secret security number as a key so that the decryption process is the reverse of the encryption process; and (3) storing the second cipher as the check number PCN in a machine-accessible location, which may be in a separate memory or recorded on the card itself. Verification is accomplished by (a) sensing the PAN from the machine-readable indicia on the card; (b) enciphering the PAN with respect to the data encryption process under control of a key which is a combination (such as by addition) of the PIN and the secret security number to thereby produce a third cipher; (c) sensing the PCN from the machine-accessible location; (d) enciphering the PCN with respect to the data encryption process under control of a key which is the secret security number to thereby produce a fourth cipher; and (e) accepting the card as valid provided the third and fourth ciphers bear a predetermined relationship to each other, such as equality.

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First Claim