Abstract: Credit cards to be used with automated systems such as vending machines or the like have various identification and other data encoded on them for use with a particular system for which they are intended. To prevent persons familiar with the system operation and the manner of encoding data on such credit cards from developing unauthorized cards which will work in the system, a random number generator is used to produce a mask for relocating the bits of encoded data in a random manner to various locations on the credit card. This mask is stored in a microprocessor memory and is used both in encoding and decoding such cards.

Abstract: In an information computer and data processing system where transactions controlled by the system are initiated and set up by a card inserted to a magnetic strip card reader, provisions are made to terminate the transaction and set the card out of the reader in response to certain conditions of the data supplied by the card reader to the system. Each card to be used with the system has a start character encoded at the beginning of characters corresponding to unique variable data identified by that card. An end character always appears at the end of the unique variable data, followed by an LRC (longitudinal redundancy check) character. Each character on the card also is provided with a parity check bit and a provision is made for detecting a parity or LRC error to terminate the transaction and to set the card out of the reader and to similarly terminate the transaction and set the card out of the reader whenever an end character is detected before a start character.