ParagonIE\Halite\File::encryptData PHP Method

    protected static function encryptData(ReadOnlyFile $input, MutableFile $output, EncryptionKey $key) : int
    {
        $config = self::getConfig(Halite::HALITE_VERSION_FILE, 'encrypt');
        // Generate a nonce and HKDF salt
        $firstNonce = \Sodium\randombytes_buf($config->NONCE_BYTES);
        $hkdfSalt = \Sodium\randombytes_buf($config->HKDF_SALT_LEN);
        // Let's split our key
        list($encKey, $authKey) = self::splitKeys($key, $hkdfSalt, $config);
        // Write the header
        $output->writeBytes(Halite::HALITE_VERSION_FILE, Halite::VERSION_TAG_LEN);
        $output->writeBytes($firstNonce, \Sodium\CRYPTO_STREAM_NONCEBYTES);
        $output->writeBytes($hkdfSalt, $config->HKDF_SALT_LEN);
        // VERSION 2+
        $mac = \Sodium\crypto_generichash_init($authKey);
        \Sodium\crypto_generichash_update($mac, Halite::HALITE_VERSION_FILE);
        \Sodium\crypto_generichash_update($mac, $firstNonce);
        \Sodium\crypto_generichash_update($mac, $hkdfSalt);
        \Sodium\memzero($authKey);
        \Sodium\memzero($hkdfSalt);
        return self::streamEncrypt($input, $output, new EncryptionKey(new HiddenString($encKey)), $firstNonce, $mac, $config);
    }