ecc.go
func (es *EccSigner) Decode(buf []byte, obj interface{}) error {
	return es.alg.Decode(es, buf, obj)
}
func (es *EccSigner) Decode(buf []byte, obj interface{}) error {
	return es.alg.Decode(es, buf, obj)
}
// Decode decodes a serialized token, verifying the signature, storing the
// decoded data from the token in obj.