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Strategic insights
Usability of Codes

Written by on July 2, 2008

Today I received a letter from my insurance company. They asked me if they could get my approval for sharing my insurance data between the companies in the insurance group. This is a quite common request, as it is illegal to share financial data without approval (in this country).

They then wanted me to sign-in to a special website, with my social security number and a special PIN code. It should be a simple thing to do, but it wasn't. The PIN was filled with 0O1l's. No matter how many times I tried, I wasn't able to guess the right combination of letters and numbers.

I eventually gave up trying to guess if O0 was and zero-O or O-zero, of if lRTl was one-R-T-one, one-R-T-I or something, and finally decided to send them a snail-mail letter instead. It is amazing that a simple operation could be such a failure simply because of a hard-to-use pin number.

It reminds me of 8 tips to serial numbers by Seth Godin:

  1. Don't use 0 or 1 or O or I in serial numbers that combine letters and numbers. 0O1I42 is asking for trouble.
  2. Never run a string of more than three identical numbers in a row. 89355555232 is bound to be a problem.
  3. Don't be case sensitive.
  4. Print the serial number larger than you think you need to. If you want the user to be able to read it to you, make it big. Then increase the size.
  5. Think hard about whether you need a serial number at all. An email address is easier to remember and just as unique.
  6. The number itself can carry useful data, like date of manufacture. If you're selling to business users, figure out how to integrate the serial numbers with their systems so they can coordinate with PO and other data.
  7. [David suggests you break up your long numbers with dashes. 108-23-2219.]
  8. With computers doing the heavy lifting, you can use serial words instead of serial numbers. If you have a combination of two words in a row, 100 words times 100 words is 10,000 combinations.

I especially like the last tip; to use words instead of numbers. Just as a pass-phrase is more usable than a password, so is a serial-phrase more usable than a serial number (or a PIN code).

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Thomas Baekdal

Thomas Baekdal

Founder of Baekdal, author, writer, strategic consultant, and new media advocate.

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