-snip sophisticated checksum suggestions-- >Sorry about my LongWindedness, just a birth defect I guess. :>) > >rp rp: No, on the contrary -- all of your suggestions were excellent. In fact, you think they way that I do. For example, in one of my programs, I placed a number in within the first 500 bytes of a PICT file (which is not used for anything that I am aware) and used that number as a security key so that anyone with ResEdit could not replace my splash screen -- or at least slow them down. Also, in another program within the preference file, I kept user data. However, I added a checksum value that was computed with an equation that used a SRQ. I think that it would have been a hard thing to crack. tedd ___________________________________________________________________ <mailto:tedd@...> http://sperling.com/