## 22 September 2012

### Popular (and unpopular) 4-digit PIN codes

Everyone knows that "1234" is an overused 4-digit PIN (the three most commonly used numbers account for almost 20% of all passwords).  Some excerpts from a Slate column:
On the other end of the scale, the least popular combination—8068—appears less than 0.001 percent of the time... Rounding out the bottom five are "8093," "9629," "6835," and "7637," which all nearly as rare...

Data Genetics came up with the numbers by analyzing a database of 3.4 million stolen passwords that have been made public over the years. Most of these are passwords for websites...

Among seven-digit passwords, the fourth-most popular is "8675309," which should ring familiar to fans of '80s music.

The 17th-most popular 10-digit password is "3141592654."

1. As a teenager of the 90's who happened to be named "Jenny" I have made it my personal mission to one day seek out Tommy Tutone and give him a punch in the snoot.

2. I'm looking at the list of the 20 least popular PINs (in the Data Genetics blog post linked to from the Slate article).

The least popular PIN that forms a simple geometric pattern on the keypad and is easy to type is 6835 at #9997. Another nicely regular one not far behind is 8957 at #9991.

The least popular PIN that contains a double digit is 8557 at #9980. We're always advised not to choose PINs that contain double digits, but here's a counterexample to the underlying assumption. It is also easy to get the fingers around.

So then, 6835, 8957 and 8557 are three PINs that (at the time the database was compiled) best balance rarity with ease of typability.

1. ? I don't understand why one 4-digit number would be easier to type than another 4-digit number.

3. I take it as axiomatic that almost everyone uses their pointer finger for the digits 1, 4 and 7, their middle finger for the digits 2, 5, 8 and 0, and their ring finger for the digits 3, 6 and 9. If you tell me that you don't do this, I will be surprised.

Given that, a number is easier to type if you don't have to move the fingers very far between one digit and the next, and as a corollory to that, if you alternate the fingers so that while one finger is pushing a button, the next can get ready. For both reasons, a PIN that includes a 0 adjacent to a 2 would be relatively difficult.

I don't know how to explain it any better than that.

1. That explains it. You have some serious data entry/bookkeeping skills or experience. I am a touch typist on the keyboard, but for numbers I'm hunt-and-peck. So you and I manage a keypad in different ways. Thanks, Adrian.