Becarfull using the unknown! It may take a long time!
It starts at the very beginning and tests every possible key code until the message is decoded.
Does not have to return original message.
Only looks for the terminator, and returns at that point.
Does not garuantee successfull decoding.

To calculate approximate time to decode without knowing keyword,(approximate successfull decode, not just finding terminator)
time is somewhere between 96^(keyLength - 1)*0.1098 and 96^(keyLength)*0.1098 seconds.
Again this is an approximation and does not take into account actual characters in key code.