When starting FitNesse you may specify a Password File by using the -a command line argument. A Password File consists of one username and password per line in the form of username:password.

Human Readable Passwords

This simple way to create a password file is to list each username:password pair as plain text in the Password File. However this is not very secure in that anyone who is able to read the Password File will have access to everyones password. Here's an example:

4 users are defined here. Leonardo whose password is Katana, Donatello whose password is bo, Rafael whose password is sai, and Michaelangelo whose password is nunchaka.

Hashed Passwords

A password hashing program, similar to unix's passwd command, is provided with FitNesse. The Password program has the following usage:
Usage: java fitnesse.authentication.Password [-f <password file>] [-c <password cipher>] <user>
        -f <password file> {passwords.txt}
        -c <password cipher> {fitnesse.authentication.HashingCipher} 

By using the Password program with default setting and using the same usernames and passwords as above, the file passwords.txt will be generated with the following content:

You can see that the passwords have been hashed and are not humanly readable. You may also notice a new line.
This should be left as is in the file. It tells the program with Password Cipher to use when hashing the passwords. You may create your own Password Cipher by implementing the fitnesse.authentication.PasswordCipher interface and use it for creating password files using the -c command line argument.