subjectUniqueID = null,
          extensions = extensions(),
        )

      // Signature.
      val signature =
        Signature.getInstance(tbsCertificate.signatureAlgorithmName).run {
          initSign(issuerKeyPair.private)
          update(CertificateAdapters.tbsCertificate.toDer(tbsCertificate).toByteArray())
          sign().toByteString()
        }

      // Complete signed certificate.