This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Note that MD5 is not a cipher (an "encryption"), but a hash. Once something has been run through MD5, there is no way of getting back the original text. The best you can do is run something else through MD5, and then compare the result with the original hash. That may or may not be what you're looking for.