func (k *ecdsaPrivateKey) SKI() (ski []byte) {
	if k.privKey == nil {
		return nil
	}
	raw := elliptic.Marshal(k.privKey.Curve, k.privKey.PublicKey.X, k.privKey.PublicKey.Y)
	hash := sha256.New()
	hash.Write(raw)
	return hash.Sum(nil)
}
SKI returns the subject key identifier of this key.
package sw
import (
	"crypto/ecdsa"
	"crypto/x509"
	"fmt"
	"crypto/sha256"
	"errors"
	"crypto/elliptic"
	"github.com/inklabsfoundation/inkchain/bccsp"
)
type ecdsaPrivateKey struct {
	privKey *ecdsa.PrivateKey
}
func (k *ecdsaPrivateKey) Bytes() (raw []byte, err error) {
	return nil, errors.New("Not supported.")
}