reverse engineering properitary linux apps

Assembly

Hi!

I'm quite new in this area but I wonder what possibilities I have to disassemble a Linux application in order to reveal an underlying Blowfish encryption. Unfortunately my target app is closed source and only runs on a properitary Linux distribution but I have root-access using RLogin/SSH.

I've tried to run IDA directly on the machine and also spotted the relevant section or at least some interesting instructions but the target process always terminates when it reaches one of my breakpoints :-(

Are there any other possibilites besides IDA to debug/step an Linux application?

chris