I want to create a visio diagram to explain encryption

[Psy]

Are there any Visio plugins/resources that might help me with this project,
looking for symbols to represent keys, plaintext and cyphertext.
All help is welcome

 

[Paul Herber]

Are there any Visio plugins/resources that might help me with this project,
looking for symbols to represent keys, plaintext and cyphertext.
All help is welcome

I've been looking at Twofish encryption recently, there is a diagram
at
http://en.wikipedia.org/wiki/Twofish

They use just plain boxes.