If you own a that has never been updated past firmware 3.41 or 3.55, a PS3 Dkey can be a nostalgic way to see how "day one" modding felt. It’s a piece of history, not a practical tool.
The PS3's D-Key: A Comprehensive Overview ps3 dkey
If you want to permanently decrypt an ISO to a "folder format" or a decrypted ISO, you can use tools like PS3Dec or PS3 Quick Disc Decryptor . If you own a that has never been updated past firmware 3
The most common way to handle these files is using a tool called ps3 dkey