I was looking for information on signing Unreal’s Pak files and couldn’t find a concise description of the steps required and information needed. Now that I have it solved, I’m making it available here.
For reference we are on version 4.17 of Unreal.
Background
Epic uses 128 bit RSA keys for signing their Pak files and 128 bit AES for encryption. The keys are added to the *Encryption.ini files for your project (like DefaultEncryption.ini) found in your <project>/Config directory.