TUCoPS :: Scams
:: crdtcksm.txtHow to calculate credit card checksums! |

Major credit card companies use the last digit in the card number as the checksum. The actual algorithm runs thru the card number, left to right, one digit at a time. Each digit is multiplied by using the sequence (2, 1, 2, 1, 2...), that is, the first digit is multiplied by 2, second by 1, the third by two and so on. If the result of the multiplication is greater than 9, the individual digits of the result are added together (i.e. the result is 17, so 1 + 7 = 8). This process is performed for each digit of the card. The result of the process for each digit is added together to give us a 'Total'. The final calculation is... Checksum = ((TotalFromAbove + 9) \ 10) * 10 - TotalFromAbove This 'checksum' will match the last digit of the card i f the card is valid. Charles -- Maximus-CBCS v1.02 * Origin: Aronson Consulting: TIDMADT 703-370-7054, voice=x6508 (1:109/120)