3 ms·
The last 4 digits are known, and the first 6 digits are based on the type of card (VISA/MC/AMEX + Bank/Issuer), so are guessable. Apply the Luhn algorithm to t
by bluesmoon 13y ago
The last 4 digits are known, and the first 6 digits are based on the type of card (VISA/MC/AMEX + Bank/Issuer), so are guessable. Apply the Luhn algorithm to these, and you're left with only 10-100K possibilities for the remaining middle digits.
If you're only required to specify the last 2, you can narrow it down significantly by only looking at valid combinations of those last 2, which is far smaller than 100.
I've written up some of this here: http://tech.bluesmoon.info/2011/01/how-guessable-is-your-credit-card.html http://tech.bluesmoon.info/2011/01/how-guessable-is-your-cre...