PIN Length
The concept of a PIN originates with the inventor of the ATM, John Shepherd-Barron. One day in 1967, while thinking about more efficient ways banks could dispense cash to their customers, it occurred to him that the vending machine model was a proven fit. For authentication Shepherd-Barron at first envisioned a six-digit numeric code, given what he could reliably remember. His wife however preferred four digits, which became the most commonly used length. ISO 9564-1, the international standard for PIN management and security, allows for PINs from four up to twelve digits, but also notes that "For usability reasons, an assigned numeric PIN should not exceed six digits in length."
Apart from financial uses, GSM mobile phones specify a PIN of between four and eight digits. The PIN is recorded in the SIM card.
Read more about this topic: Personal Identification Number
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