A mathematician at the University of Minnesota-Duluth has cracked the code and found meaning in the 12 numbers on every Minnesotan's driver's license.

The code has been in use for decades and, as far as anyone knows, Joseph Gallian is the first person to figure it out on his own. State officials say that the formula is public information but that they don't advertise it for fear of aiding fraudulent use of license numbers.To prove his virtuosity with the numbers, Gallian, who explained his discovery in the current issue of Mathematics Magazine, asked a journalist for his full name and the day and month of his birth. After a few minutes of paper shuffling and figuring, Gallian came up with the correct 12-digit driver's license number. That is the information hidden in the four three-digit groupings on the license: last name, first name, middle name and day and month of birth.

The first three numbers, which hold a person's last name, are based on an odd system developed for the 1920 Census. Letters in the name are assigned numbers, but it isn't quite that simple. The letters "H" and "W" don't count because the system developers knew those letters were often silent and not written down when names were given verbally to immigration or census officials.

Vowels stay in the formula for the moment but get no numbers assigned to them. The letters B, F, P and V are given a 1. The letters C, G, J, K, Q, S, X and Z are given a 2. The letters D and T get a 3; M and N get a 5; L a 4, and R a 6.

If two or more letters are adjacent and have the same numerical value, delete all but the first one. Vowels count as spaces separating other letters at this point.

Now, delete the first letter of the name if it is still there, then get rid of all the vowels. The first three numbers assigned to the remaining letters are the first three numbers on your driver's license. If there are fewer than three numbers remaining, add a zero to get the number.


Figuring out the remaining numbers involves code books that match letter combinations with numbers. In Minnesota, for example, a first or middle name beginning with "Ab" would be assigned 029. It quickly gets more complicated to assure that people with identical names don't get the same number, Gallian said.

The quest to break the code began one morning several years ago as Gallian was trying to figure out the bar code on a box of corn flakes. It was pretty simple stuff, he said, with numbers standing for the company, the country and the name of the product. But there was one other number, one that he later found was an "error detection scheme" to stop store clerks from entering the code incorrectly.

Then a friend told him there was a state with the same error scheme on its drivers' licenses, and Gallian was off on his code-cracking adventure. He wrote to all 50 states, asking for the driver's license numbering systems. But Minnesota state officials wouldn't give him the code. It's a secret, they said.

Gallian tried and tried to crack the code on his own but failed. Then he noticed that the elaborate system used in Michigan, which officials from that state willingly explained, seemed similar to Minnesota's. He applied the mathematical algorithms and Michigan codes to the Minnesota numbers and they worked.

"Minnesota has the most interesting scheme in the country, and they keep it secret," Gallian said.

Well, not quite secret, said Pierre Carpenter, chief of licensing for Minnesota. He said he has no doubt Gallian was told the information was secret, but after Department of Public Safety officials discussed the matter this week, they decided that the codes behind the license numbers aren't secret - sort of.

"It's public information, and we have no trouble giving it out," Carpenter said. Then again, he added, the department won't give it out to just anyone that walks in off the street. People must show "just need" for the information.

Nobody other than Gallian has ever asked for the codes, Carpenter says, so a real policy never has had to be developed.