signature/mechanism_openpgp.go
func newEphemeralGPGSigningMechanism(blob []byte) (SigningMechanism, []string, error) {
	m := &openpgpSigningMechanism{
		keyring: openpgp.EntityList{},
	}
	keyIdentities, err := m.importKeysFromBytes(blob)
	if err != nil {
		return nil, nil, err
	}
	return m, keyIdentities, nil
}
func newEphemeralGPGSigningMechanism(blob []byte) (SigningMechanism, []string, error) {
	m := &openpgpSigningMechanism{
		keyring: openpgp.EntityList{},
	}
	keyIdentities, err := m.importKeysFromBytes(blob)
	if err != nil {
		return nil, nil, err
	}
	return m, keyIdentities, nil
}
// newEphemeralGPGSigningMechanism returns a new GPG/OpenPGP signing mechanism which
// recognizes _only_ public keys from the supplied blob, and returns the identities
// of these keys.
// The caller must call .Close() on the returned SigningMechanism.