Ever since I wrote the articles on “Meaning of Numbers on a Debit or Credit Card” and “How To Find If A Credit Card Is Fake”, one thing continuously nagged me- Why are the card numbers so long? Apart from making it difficult for us to remember Won’t it increase the chances of someone accidently typing your card number instead of theirs while making an online transaction?
This is done for added security. So that probability of fraudsters coming up with correct card numbers is very less. Let’s understand this in detail.
How many possible values can be there for a 2-digit number? The answer is 100- from 00, 01 and so on till 99. Or to make it more simple, its 10^2, i.e. 100. Similarly for a 3-digit number, possible combinations of values is 1000- 000 to 999, or 10^3.
Card number is generally 16 digits long. So the number of possible 16 digit numbers is 10^16. If every individual of the world owns a card, even then total number of cards will be 10 billion (assuming world’s population to be 10 billion- it is presently close to 7 billion). The probability that a fraudster manages to correctly guess a card number is (10 billion)/ (10^16) = 0.0001% – 1 out of 1 million !!
Of course this does not mean that you should become careless with your card. For there are many other ways one can be conned into revealing sensitive information about credit cards and bank details. So never let your guard down. Oh and please don’t believe someone who tells you that entering your card PIN in reverse in an ATM will bring help- because it is just a popular hoax.
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