Easy Decoder Ring is a fast and free app to encode and decode text based on a cypher key (password) you specify.

Simply enter your cypher key (password) and encode/decode the text! Easy Decoder Ring is as simple as the old decoder rings of yore, yet based on modern AES encryption technology.

You can download it from the Android Market here.

Update 4/2012 This is now open source and hosted on GitHub. Check it out at my GitHub page.