Friday, October 19, 2012

credit card number

Learning Where The Numbers Come From

Credit card numbers are not random. There's a special set of numbers to show information about the card issuer and another set to show information about the card holder. One other number is also important, but we'll come to that later.

The very first number is the Major Industry Identifier (MII) and it tells you what sort of institution issued the card.

  • 1 and 2 are issued by airlines.
  • 3 is issued by travel and entertainment.
  • 4 and 5 are issued by banking and financial institutions.
  • 6 is issued by merchandising and banking.
  • 7 is issued by petroleum companies.
  • 8 is issued by telecommunications companies.
  • 9 is issued by national assignment.

The first six digits are the Issuer Identification Number (IIN). These can be used to look up where the card originated from. If you have access to a list that details who owns each IIN, such as this list of popular IINs on Wikipedia, you can see who issued the card just by reading the card number.

Here's a few you might recognise:

  • Visa: 4*****
  • American Express (AMEX): 34**** or 37****
  • Diner's Club International: 36****
  • Mastercard: 51**** to 55****

The seventh digit to the second-to-last digit is the customer account number. Most companies use just 9 digits for the account numbers, but it's possible to use up to 12. This means that using the current algorithm for credit cards, the world can issue about a trillion cards before needing to change the system.

understand credit card numbers

We often see 16-digit credit card numbers today, but it's possible for a card issuer to issue a card with up to 19 digits using the current system. In the future, we may see longer numbers becoming more common.

The very last digit of each credit card is the check digit, or checksum. It is used to validate the credit card number using the Luhn algorithm, which we will now explain in detail.

The Luhn Algorithm Validation Check

The Luhn Algorithm is used to validate all sorts of numbers, including credit cards, IMEI numbers and some social security numbers. It's not designed to be a cryptographically secure hash function, but merely a way to check errors are not made when recording numbers. It is not foolproof, but is generally considered to be useful.

Take the credit card number and read the digits from the right. Double every other number and write them down – if you do it in the same order as your card is written it will help with clarity. Now, wherever you have calculated a double-digit number, change it so that it reads as "first digit + second digit" (in other words, sum the digits of the products). Finally, take your calculations and add those numbers to the numbers remaining on your card that you didn't double. A legitimate credit card number will give you a result that is divisible by 10.

For instance, let's use a number I've just made up: 4634 8932 1298 2767. I'll enter it into a table to make it easier to understand the steps.

understand credit card numbers

Try it yourself using the card from the picture earlier in this article. What can you learn from it?

Wednesday, June 27, 2012

MobileMe is moving to the iCloud

MobileMe is moving to the iCloud.
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MobileMe is moving to the iCloud

If you're a MobileMe user, you've probably been seeing one of these emails daily. Since the MobileMe service is being discontinued, we will no longer be able to offer syncronization with your MobileMe files in Otixo.
We won't immediately delete your MobileMe account from Otixo, but it will stop syncronizing. To remove your MobileMe account from Otixo, please right click on the MobileMe icon and select "Remove".

Otixo & the iCloud

Unfortunately, Apple hasn't released a web API for the iCloud, which is why we haven't included it in Otixo. We're keeping our fingers crossed that they release one soon, but we think we're just going to end up getting arthritis.

Good News

Since this email is a bit of a downer, we can't help but give you a hint about a coming-soon Otixo integration. We sure hope you're fans of CX, because we are. Who doesn't love 10 GB of free storage? ;)
Happy Otixoing,
-The Otixo Team

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Wednesday, May 30, 2012

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Wednesday, April 18, 2012

Fw: handy tips

---------- Forwarded message ----------
From: Ranjit Santakumar
Date: Wed, Apr 18, 2012 at 10:22 AM
Subject: Fw: handy tips




Definitely great ideas!
You will definitely utilize at least 3 of the following ideas!
Some really useful ideas in here - especially the first one since I always hit a finger!!  Now, why didn't I think of that?


Wednesday, April 04, 2012

DropBox !

Always have your stuff when you need it with @Dropbox. 2GB account is free!

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