}

func certificateIdentifier(c *x509.Certificate) string {
	return fmt.Sprintf(
		"SN=%d, SKID=%s, AKID=%s",
		c.SerialNumber,
		columnSeparatedHex(c.SubjectKeyId),
		columnSeparatedHex(c.AuthorityKeyId),
	)
}

// VerifyOptionFunc is function which provides a shallow copy of the VerifyOptions to the authenticator.  This allows