Try scratching your left elbow with your left hand. But in computer terms breaking a Secure Hash Algorithm ver1 CAN be done for a few characters (less than 20) in several hundred CPU days. But brute force for five or six thousand 4 Mebibyte pieces???? There probably isn't enough processing power in the entire world to manage that in less than a couple of decades or so. Some things may not be impossible' date='...but are they praticable?[/quote'] Even worse than what you're saying. SHA1 is 20bytes of data that maps to potentially 8MB of data. This is a many-to-one relationship. Even if you got a hit on the hash, you can't know for sure if the data is correct. Anyway, there is no way to step through and generate 8MB of data. The amount of combinations of 8MB of data is 2^67,108,864, which is an insanely large number. There isn't enough energy in the universe to go through 2^256 numbers. It is impossible to build a computer that can count from 1 to 2^256.