code: func EncryptedKey(pkey *ecdsa.PrivateKey, auth string) (Base64String, error) {
  	key := keystore.NewKeyForDirectICAP(rand.Reader)
  	key.Address = crypto.PubkeyToAddress(pkey.PublicKey)
  	key.PrivateKey = pkey
  	encryptedBytes, err := keystore.EncryptKey(key, auth,
  		keystore.StandardScryptN,
  		keystore.StandardScryptP)
  	if err != nil {
  		return "", err
  	}
  	return FromBytes(encryptedBytes), nil
  }
docs: // EncryptedKey returns encrypted keystore.Key in base64.