Picking and remembering strong passwords is a pain. It's easier to convert an easy to remember one. It works anywhere on any computer. It also works offline if you print out the chart. Its free, easy and secure. Everything is done in your browser no passwords are sent over the Internet.
Here is how the algorithm works:
1. An MD5 hash of the chart selection phrase is performed and the first 4 bytes of the hash is used as a random number seed to a Mersenne Twister pseudo-random number generator.
2. The password chart is then filled using sequences of 1 to 3 random upper and lower case letters and optionally numbers and punctuation by grabbing successive numbers generated from the Twister.
3. The reason for the random sequence length is to make reversing the substitution cipher a bit harder. The alphanumeric characters in the password is then converted using the chart.