A personal identification number (PIN) is a code which an individual can use to access electronically secured information. The code is usually four digits, but can be longer. It is most commonly used with credit and debit cards at automatic teller machines (ATMs) and in retail stores. They are also used for online access to a variety of accounts and other forms of sensitive information.
The Scottish engineer James Goodfellow invented and patented the PIN number. He also came up with one of the first ATM designs, though inventor John Shepherd-Barron's design of the ATM was used for early machines. PIN numbers were first used for an early version of the machine in the mid-1960s. The original concept was to use six-digit numbers as a standard, but before they were put into wide use, the number was reduced to four. Though a PIN can now be up to 12 digits, typical international standards advise using codes that are six figures or less.
Many institutions will generate their own codes for customer use. There are several ways that this can be done. A common practice is to encrypt the account number so that the PIN number will seem random, but is really significantly connected to the customer.
Some institutions will let a customer select their own PIN, but generate a code known as an offset which is added to the digits selected by the customer before it is stored in the bank’s database. This adds an extra level of security while granting the customer some flexibility. Many institutions will also only allow a customer to try entering a PIN a limited number of times before denying any further attempts until the code is either reset or the user contacts customer service.
If the user is not given a pre-generated PIN number, there are several ways to create a code that is easy to remember, but difficult to guess or hack. Most PINs are limited to four digits, but if there is the option to use more numbers, this alone can help to significantly increase security. Another method is to select a word and pick the corresponding numbers from the keys on a phone. If the numbers are arranged in an unpredictable way, selecting a significant date to be the PIN can also work — though it is not advisable to pick a birthday, wedding date, or other obvious date of importance to the user. Another way to create a strong PIN number is to pick a significant number and then add a specific amount, such as one, two, or three to each digit of that number.