Aza:
Bitwise xor.
I don't know if Blitz3D has that operation though. There may be a function in the math section of the code archives here that will do it if not.
You could also just add some number on encrypt and then subtract that number later IF you're working with whatever the int type in Blitz3D is. I think Blitz3D uses longs. So if you load the file as longs, and add 10 then the number will roll over to negative if it's too high, and roll back to positive when you subtract form it again. That's what numbers on computers do when you exceed the highest value they can hold.
But if your file isn't an even multiple of 4 bytes in size then you'll have to stick some zero bytes into that last int, so once again things aren't gonna be so easy for you.
Bitwise xor.
I don't know if Blitz3D has that operation though. There may be a function in the math section of the code archives here that will do it if not.
You could also just add some number on encrypt and then subtract that number later IF you're working with whatever the int type in Blitz3D is. I think Blitz3D uses longs. So if you load the file as longs, and add 10 then the number will roll over to negative if it's too high, and roll back to positive when you subtract form it again. That's what numbers on computers do when you exceed the highest value they can hold.
But if your file isn't an even multiple of 4 bytes in size then you'll have to stick some zero bytes into that last int, so once again things aren't gonna be so easy for you.