Well what we were doing for pe encryptors (will try to dig out some code from tapes when I get back into civilization :D) was generating a code that was driving

Well what we were doing for pe encryptors (will try to dig out some code from tapes when I get back into civilization :D) was generating a code that was driving execution flow using SEH (structured exception handling), sometimes the code executed as intended, sometimes the exception was trigered (with faulty code, again generated) to continue at completely different part of code. This was the complete pain in the "neck" to debug (timing the code execution is a great way to tell if someone is debugging it, and you just continue into some other generated code that is missleading the reverser), and completely impossible to solve on paper (well, with huge amount of knowlidge and a lot of time, you could do it :D). That's why I am laughing with todays overuse of try/catch/throws, we were using it to obfuscate execution flow and today it is used in normal coding with same devastating effect :D