While MD5 may not be the most effective way to secure data, it is used by some database applications and other systems. For more info on MD5, you can check: http://en.wikipedia.org/wiki/MD5
Once in a while, when configuring password sync/reset support for applications and systems for a given project, we stumble on MD5 hashed values.
I am storing the value to be hashed in a local variable called MD5Pwd in the action before the action that actually hashes the value, using $MD5Pwd as the argument for my calcMD5 function.
MD5 hash is not reversible(in theory) so we can use this example to provide support for password reset, and password check, but not to obtain the original value(before hash) on the Publisher channel for password sync.