It's because I store "unique" files and the best way to ensure and quickly check that (without a db or additional db-file) is to simply save them with the checksum as the name.

As for the collission, I tought about that before. I think I'll add another checksum algo, SHA, to the name.
Using two independent algorithms should save me from any collission. Then it's more likely the whole building tunnels into another universe spontanously.