/// <summary>
        /// Add a certificate to the identity storage. Also call addKey to ensure that
        /// the certificate key exists. If the certificate is already installed, don't
        /// replace it.
        /// </summary>
        ///
        /// <param name="certificate"></param>
        public override sealed void addCertificate(IdentityCertificate certificate)
        {
            Name certificateName = certificate.getName();
            Name keyName = certificate.getPublicKeyName();

            addKey(keyName, certificate.getPublicKeyInfo().getKeyType(),
                    certificate.getPublicKeyInfo().getKeyDer());

            if (doesCertificateExist(certificateName))
                return;

            // Insert the certificate.
            try {
                PreparedStatement statement = database_
                        .prepareStatement("INSERT INTO Certificate (cert_name, cert_issuer, identity_name, key_identifier, not_before, not_after, certificate_data) "
                                + "values (?, ?, ?, ?, datetime(?, 'unixepoch'), datetime(?, 'unixepoch'), ?)");
                statement.setString(1, certificateName.toUri());

                Name signerName = net.named_data.jndn.KeyLocator.getFromSignature(
                        certificate.getSignature()).getKeyName();
                statement.setString(2, signerName.toUri());

                String keyId = keyName.get(-1).toEscapedString();
                Name identity = keyName.getPrefix(-1);
                statement.setString(3, identity.toUri());
                statement.setString(4, keyId);

                // Convert from milliseconds to seconds since 1/1/1970.
                statement.setLong(5,
                        (long) (Math.Floor(certificate.getNotBefore() / 1000.0d)));
                statement.setLong(6,
                        (long) (Math.Floor(certificate.getNotAfter() / 1000.0d)));

                // wireEncode returns the cached encoding if available.
                statement.setBytes(7, certificate.wireEncode().getImmutableArray());

                try {
                    statement.executeUpdate();
                } finally {
                    statement.close();
                }
            } catch (SQLException exception) {
                throw new SecurityException("BasicIdentityStorage: SQLite error: "
                        + exception);
            }
        }