Generate a Strong PIN Code

Research published by security analysts who study leaked credential corpora consistently shows that a startling proportion of all four digit PINs in active use are drawn from a very small set of predictable values. The often cited DataGenetics analysis found that the top twenty most common four digit PINs account for over a quarter of every PIN observed across leaked datasets. Numbers like 1234, 1111, 0000, 2580, 1212, and any value resembling a recent birth year dominate the distribution. The implication for an attacker is profound. When a phone is stolen or a card is skimmed, the first combinations they try are these top values, and within a handful of attempts they have a meaningful probability of unlocking the device or completing a fraudulent transaction. A randomly generated PIN eliminates this bias completely because every combination is equally likely, and an attacker who knows nothing about you gains nothing by trying anything else first.

The mathematics of PIN security scale very sharply with length, and this is the single most important lever you have when choosing how long a PIN to use. A four digit PIN has exactly ten thousand possible values. A six digit PIN has one million possible values, which is precisely one hundred times more. An eight digit PIN has one hundred million possible values, ten thousand times more than a four digit PIN. Modern smartphones support six digit PINs as the default and many banking apps, authentication tokens, and physical access systems now offer six digit PIN options for users who want them. When a system gives you a choice between four and six digits, almost always choose six. The security improvement is substantial, the memorisation cost of two additional digits is minimal once you have used the PIN a few times, and the typing time is essentially identical because the extra keystrokes take fractions of a second.

Memorising a random PIN is far easier than people expect when they first encounter the idea. The most reliable technique is chunking, where a six digit PIN like 847362 is committed to memory as the three two digit pairs 84, 73, and 62 rather than six independent symbols. The human short term memory comfortably holds three or four chunks, so a six digit PIN expressed as three pairs sits comfortably within that capacity and becomes reliable after a handful of repetitions. Another effective technique is associating the digits with a physical pattern on the keypad, learning the rhythm of the taps rather than the numerical value. Within a day or two of regular use, the PIN becomes muscle memory and you no longer have to think about the digits at all. As a safety net during the learning period, store the PIN as an encrypted note in your password manager so you have a recovery option in case you draw a blank at an inconvenient moment.

It is worth understanding the threat model that PIN security defends against. Unlike passwords, which often face offline attacks against leaked hashes at billions of guesses per second, PINs almost always face online attacks through a real device or terminal that imposes severe rate limits. Banks lock cards after three wrong attempts. Phones lock after between five and ten incorrect entries before requiring a longer wait, a biometric override, or a full device wipe. These constraints mean that PIN security is principally about resisting casual guessing rather than industrial brute force. A truly random PIN exploits this favourable threat model fully, giving an attacker no way to bias their handful of attempts toward likely values. A predictable PIN, by contrast, surrenders this advantage and can be defeated within the small number of attempts that the lockout policy permits.