Everybody have at least a credit card in their wallet. We know for sure that this card is useful. But how much do we know about these cards.
Here is a little trick about how the numbers are generated and how to validate a credit card.
Let’s get started.
Major Industry Identifier
The first digit is the Major Industry Identifier.It designates the category of the entity which issued the card.
1 and 2 are airlines
3 is Travel and entertainment.
4 and 5 are banking and financial
7 is petroleum
8 is telecomunications
9 is national assignment.
Issuer Identification Number(IIN)
The first 6 digits are Issuer Identification Number. It will identify the institution that issued the card.
Mastercard 51xxxx – 55xxxx
Discover 6011xx, 644xxx and 65xxxx
Amex 34xxxx and 37xxxx
Cards can be looked up by their IIN. A card that starts with 37621 is a Singapore airlines krisflyer American express gold card. 529962 designates a prepaid Much music mastercard.
Person’s account number
The 7th and following digits , excluding the final digits are the person’s account number. This leaves a trillion possibilities if the maximum of 12 digits is used. Most cards use just 9 digits.
The final digit is the check digit or checksum. It is used to validate the credit card number using the Luhn algorithm.
How to validate a credit card.
Lets take the above credit number for example:
7 2 5 3 3 2 5 6 7 8 9 5 1 2 4 5
And double every other digit from the right
(7×2) 14 (5×2) 10 (3×2) 6 (5×2) 10 (7×2) 14 (9×2) 18 (1×2) 2 and finally (4×2) 8
Add these new digits to undoubled ones
2 3 2 6 8 5 2 5
All double digits are added as a sum of their digits for example 14 = 1 + 4
It gives a total of 124
A credit card number is valid only when the final sum is divisable by 10. In the case of our example, it is a fake credit card number or an invalid one.
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