Hashes cannot be “decrypted”.
You would need to use something that allows for encryption and decryption.
You can use acf/update_field and acf/load_value filters to alter the values before it is saved and then change it back when it is loaded.
My only real advice past this is that the data should not be stored if the database in not secure and you should be looking into hosting that provides proper security dependend on what you need to be complaint with like HIPAA or PCI.
