code: func CreateCertificateKey() (string, error) {
  	randBytes, err := cryptoutil.CreateRandBytes(kubeadmconstants.CertificateKeySize)
  	if err != nil {
  		return "", err
  	}
  	return hex.EncodeToString(randBytes), nil
  }
docs: //CreateCertificateKey returns a cryptographically secure random key