Patent ID: 8249993

Claim:
A method for encrypting bank card data from a bank card presented for a purchase transaction and for presenting encrypted bank card data to a transaction processing network for the purchase, the method comprising: a point of sale bank card reader receiving a first set of bank card data from the bank card presented to the point of sale card reader for the purchase transaction, wherein the first set of data comprises clear text bank card data read from the bank card at the point of sale; the bank card reader encrypting a selected subset of characters of the clear text bank card data read from the bank card at the point of sale; the bank card reader replacing the original selected subset of characters of the card data with the encrypted selected subset of characters of the card data thereby creating encrypted bank card transaction data; the bank card reader performing a mod 10 calculation on the encrypted bank card transaction data; the bank card reader determining a digit that can be inserted into the encrypted bank card transaction data to cause a modulo 10 arithmetic check of the encrypted bank card transaction data to yield the same result as a modulo 10 arithmetic check would yield on the clear text bank card data read from the bank card at the point of sale; inserting the digit into the encrypted bank card transaction data; and forwarding the encrypted bank card transaction data with the digit to the transaction processing network for the purchase transaction.