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Personal Identification Number Checking Algorithm

IP.com Disclosure Number: IPCOM000081346D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Prudhomme, M: AUTHOR

Abstract

This algorithm generates three digits of a reference number such as an account number from a four-digit personal identification number (ID) and a four-digit key (K). This algorithm contrasts with known algorithms such as disclosed in U. S. Patent 3,657,521 wherein an account number read from an identification card is translated by an enciphering unit, to generate the personal identification number for comparison with the ID number allegedly known only by the authorized card holder, which is provided at a keyboard input.

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Personal Identification Number Checking Algorithm

This algorithm generates three digits of a reference number such as an account number from a four-digit personal identification number (ID) and a four- digit key (K). This algorithm contrasts with known algorithms such as disclosed in U. S. Patent 3,657,521 wherein an account number read from an identification card is translated by an enciphering unit, to generate the personal identification number for comparison with the ID number allegedly known only by the authorized card holder, which is provided at a keyboard input.

An advantage in the described algorithm is that it prevents an unauthorized holder of an identification card, such as a bank employee who also knows the key and the algorithm, from working backwards with the algorithm to generate the corresponding personal identification number which should be known only by an authorized card holder.

Since a decimal number requires four bit positions when represented in a binary code, the personal ID number and the key number can be stored in four registers having eight bits each as shown below:
ID1 XXXX XXXX The first two digits of the personal ID number. ID2 XXXX XXXX The last two digits of the personal ID number.

K1 XXXX XXXX The first two digits of the bank key.

K2 XXXX XXXX The last two digits of the bank key.

Each digit of the three-digit output appears as the low-order four bits of a different eight-bit register as follows: X 1111 XXXX The first output digit. Y 1111 XXXX The second output digit. Z 1111 XXXX The last output digit.

X, Y and Z are three bits of a reference number such as a bank account number, which must compare with the account number communicated or read from an identification card in order to authorize transactions against the account.

The steps of the algorithm occur in the following sequence: 1) B1 = ID1 x K1. 2) B2 = ID2 x K2. 3) ROT1 = The three-bit number defined by bit p...