code: func (k *revocationPublicKey) SKI() []byte {
  	// Marshall the public key
  	raw := elliptic.Marshal(k.pubKey.Curve, k.pubKey.X, k.pubKey.Y)
  
  	// Hash it
  	hash := sha256.New()
  	hash.Write(raw)
  	return hash.Sum(nil)
  }
docs: // SKI returns the subject key identifier of this key.