Have you managed to solve the entire Stage 5 Cipher Challenge? Solutions are now closed, but perhaps you want to take up the full challenge.

Successful solvers of this part were

Patrick from Woodbridge School, England
An Anonymous Solver from Somewhere in the US
Joseph from Hong Kong

 

The solution was:

The keyword for the last cipher was pi. The technique used in this cipher is a Caesar square. It's probably a bit obvious having a square number of characters in the message. The next one might well be a combination of the techniques used so far.