Return a copy of the passed in secret key ring, with the private keys (where present) associated with the master key and sub keys
are encrypted using a new password and the passed in algorithm.
Return the base format for this key - in the case of the symmetric keys it will generally
be raw indicating that the key is just a straight byte representation, for an asymmetric
key the format will be PGP, indicating the key is a string of MPIs encoded in PGP format.