else -> null
      }
    }

  /**
   * ```
   * AlgorithmIdentifier ::= SEQUENCE  {
   *   algorithm      OBJECT IDENTIFIER,
   *   parameters     ANY DEFINED BY algorithm OPTIONAL
   * }
   * ```
   */
  internal val algorithmIdentifier: BasicDerAdapter<AlgorithmIdentifier> =
    Adapters.sequence(
      "AlgorithmIdentifier",

    assertThat(Adapters.NULL.fromDer(bytes)).isNull()
    assertThat(Adapters.NULL.toDer(null)).isEqualTo(bytes)
  }

  @Test fun `sequence algorithm`() {
    val bytes = "300d06092a864886f70d01010b0500".decodeHex()
    val algorithmIdentifier =
      AlgorithmIdentifier(
        algorithm = SHA256_WITH_RSA_ENCRYPTION,
        parameters = null,
      )
    assertThat(CertificateAdapters.algorithmIdentifier.fromDer(bytes))

      return when (signedByKeyPair.private) {
        is RSAPrivateKey ->
          AlgorithmIdentifier(
            algorithm = SHA256_WITH_RSA_ENCRYPTION,
            parameters = null,
          )
        else ->
          AlgorithmIdentifier(
            algorithm = SHA256_WITH_ECDSA,
            parameters = ByteString.EMPTY,
          )
      }
    }

    )
  }

  /** Converts public key bytes to SubjectPublicKeyInfo bytes. */
  private fun encodeKey(
    algorithm: String,
    publicKeyBytes: ByteString,
  ): ByteString {
    val subjectPublicKeyInfo =
      SubjectPublicKeyInfo(
        algorithm = AlgorithmIdentifier(algorithm = algorithm, parameters = null),
        subjectPublicKey = BitString(publicKeyBytes, 0),
      )