That isn't really a question we can just answer - there are a huge number of ways you could do that, depending on the complexity and security you need. The only problem is the fixed size output - it is difficult to predict the size of the output since most complicated encryption systems generate "block" outputs which aren't normally 64 byte blocks.
So start here:
Wiki Encryption[
^] and branch out fvrom there using Google, or explain what you are trying to achieve, and we'll see if we can help - it may be that you are going down a completely wrong avenue! For example, if this is for passwords, then encryption is a poor idea - you should be hashing your data instead, which always produces a fixed size output, regardless of the input size.