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Creating unique credit card-like numbers

Posted on 2004-04-20
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Last Modified: 2010-04-05
I need to CREATE a number like a credit card number that will also use the same MOD10 Checksum algorithm
that a credit card uses. I have the validation routines but can't figure out how to CREATE the numbers.

Any ideas or links?
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Question by:EddieShipman
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2 Comments
 
LVL 26

Author Comment

by:EddieShipman
ID: 10872464
No, I am not generating fake credit card numbers. This is for product registration and, no, I do not want to use GUIDs.
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LVL 17

Accepted Solution

by:
mokule earned 125 total points
ID: 10873513
You must generate 15 digit number and this function will generate the 16-th rightmost digit.

function TForm1.Generate(str: string): string;
var
  i: integer;
  len: integer;
  su: integer;
  dig: integer;
begin
  len := Length(str);
  su := 0;
  for i := 0 to len-1 do
    begin
    dig := Ord(str[len-i]) - Ord('0');
    if (i mod 2) = 1 then
      su := su + dig
    else if dig < 5 then
      su := su + 2 * dig
    else
      su := su + 1 + 2 * dig - 10;
    end;
  if su mod 10 = 0 then
    Result := str + '0'
  else
    Result := str + Char(Ord('0') + 10 - su mod 10);
end;
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