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CCA Release 2.54
IBM 3624 PIN Offset Calculation Method
The IBM 3624 PIN Offset calculation method is the same as the IBM 3624
PIN-calculation method except that a step is added after the A-PIN is calculated to
calculate or use an offset, O-PIN:
To calculate an O-PIN, the additional step subtracts (digit-by-digit, modulo 10,
with no carry) the calculated A-PIN from the customer-selected C-PIN.
The result is an O-PIN (offset) of n decimal digits, where n is the PIN length
and must be in the range from 4 to 16. The PIN_check_length parameter
specifies n as the low-order (rightmost) digits of the n-digit PIN offset. The
O-PIN (offset) is not encrypted.
To use an offset to verify a trial PIN, the additional step adds (digit-by-digit,
modulo 10, with no carry) the offset to the calculated A-PIN. The result is
compared to the customer-entered trial PIN (T-PIN).
Notes:
1. The digit-wise subtraction is defined only for digits in the range from
X'0' to X'9'. Any other value is not valid and causes processing to fail.
2. The length of the offset depends on the length of the PIN and must be less
than or equal to the length of the PIN. The financial institution that issues the
magnetic-stripe card determines the length of the PIN offset, which you specify
with the PIN_check_length parameter.
3. When the length of the PIN offset is less than the length of the calculated PIN,
the subtraction or addition begins with the low order PIN digit.
E-4 IBM 4758 CCA Basic Services, Release 2.54, February 2005