PS4 SaveData Decrypting Tools in development, recent PS4 Game Saves with FPKG's Guide and his LibHB PS4 Homebrewing Library PlayStation 4 developer @cfwprophet made available PSFSKKey which is a PS4 SaveGame Decryption Tool for developers that is only missing the SAMU (Secure Asset Management Unit) PFS keys.
Download: PSFSKKey-master.zip / GIT
From the ReadMe.md, to quote: PSFSKKey
A Tool to decrypt your save games. Right now just the SAMU PFS keys are missing. Code is already added. So when either, the Keys are released or some one which have, add them, then we have a working tool already.
For encryption aka signing, reverse the steps. Get SD master keys from ps4 devwiki or use SaveDataMasterKeyDumper_v2_505.pkg (Mirror) to dump them your self from your console. Put keys into same directory then this tool run.
Credits:Code:PSFSKKey.exe SaveDataPFSSKKey.bin SaveData