get() {
      return when (signature.algorithm) {
        ObjectIdentifiers.SHA256_WITH_RSA_ENCRYPTION -> "SHA256WithRSA"
        ObjectIdentifiers.SHA256_WITH_ECDSA -> "SHA256withECDSA"
        else -> error("unexpected signature algorithm: ${signature.algorithm}")
      }
    }

  // Avoid Long.hashCode(long) which isn't available on Android 5.
  override fun hashCode(): Int {
    var result = 0