That does not sound like a question to me. That sounds like a homework assignment.
It was not very difficult to find source code for RC5, but as I cannot tell what the license is for the source, and as the source appears to include at least one algorithm that has patent restrictions, I am not comfortable posting the link. I am even less comfortable with the possibility that you are doing an assignment and intend to copy the code when your instructor probably intends that you write it yourself.
