<?php

// Примем, что ключ $key уже сформировали
$iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_CBC);
$iv = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM);
$fp = fopen('encrypted-file.enc', 'wb');
fwrite($fp, $iv);
$opts = array('mode' => 'cbc', 'iv' => $iv, 'key' => $key);
stream_filter_append($fp, 'mcrypt.blowfish', STREAM_FILTER_WRITE, $opts);
fwrite($fp, 'message to encrypt');
fclose($fp);

// Расшифровка...
$fp = fopen('encrypted-file.enc', 'rb');
$iv = fread($fp, $iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_CBC));
$opts = array('mode' => 'cbc', 'iv' => $iv, 'key' => $key);
stream_filter_append($fp, 'mdecrypt.blowfish', STREAM_FILTER_READ, $opts);
$data = rtrim(stream_get_contents($fp)); //trims off null padding
fclose($fp);
echo $data;

<?php

AES_CBC::encryptFile($password, "plaintext.txt", "encrypted.enc");
AES_CBC::decryptFile($password, "encrypted.enc", "decrypted.txt");

class AES_CBC
{
    protected static $KEY_SIZES = array('AES-128' => 16, 'AES-192' => 24, 'AES-256' => 32);

    protected static function key_size()
    {
        return self::$KEY_SIZES['AES-128'];
    } // default AES-128

    public static function encryptFile($password, $input_stream, $aes_filename)
    {
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
        $fin = fopen($input_stream, "rb");
        $fc = fopen($aes_filename, "wb+");

        if (!empty($fin) && !empty($fc)) {
            fwrite($fc, str_repeat("_", 32)); //placeholder, SHA256 HMAC will go here later
            fwrite($fc, $hmac_salt = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM));
            fwrite($fc, $esalt = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM));
            fwrite($fc, $iv = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM));
            $ekey = hash_pbkdf2("sha256", $password, $esalt, $it = 1000, self::key_size(), $raw = true);
            $opts = array('mode' => 'cbc', 'iv' => $iv, 'key' => $ekey);
            stream_filter_append($fc, 'mcrypt.rijndael-128', STREAM_FILTER_WRITE, $opts);

            $infilesize = 0;
            while (!feof($fin)) {
                $block = fread($fin, 8192);
                $infilesize += strlen($block);
                fwrite($fc, $block);
            }

            $block_size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
            $padding = $block_size - ($infilesize % $block_size); //$padding is a number from 1-16
            fwrite($fc, str_repeat(chr($padding), $padding)); //perform PKCS7 padding
            fclose($fin);
            fclose($fc);
            $hmac_raw = self::calculate_hmac_after_32bytes($password, $hmac_salt, $aes_filename);
            $fc = fopen($aes_filename, "rb+");
            fwrite($fc, $hmac_raw); //overwrite placeholder
            fclose($fc);
        }
    }

    public static function decryptFile($password, $aes_filename, $out_stream)
    {
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
        $hmac_raw = file_get_contents($aes_filename, false, NULL,  0, 32);
        $hmac_salt = file_get_contents($aes_filename, false, NULL, 32, $iv_size);
        $hmac_calc = self::calculate_hmac_after_32bytes($password, $hmac_salt, $aes_filename);
        $fc = fopen($aes_filename, "rb");
        $fout = fopen($out_stream, 'wb');

        if (!empty($fout) && !empty($fc) && self::hash_equals($hmac_raw, $hmac_calc)) {
            fread($fc, 32 + $iv_size); //skip sha256 hmac and salt
            $esalt = fread($fc, $iv_size);
            $iv    = fread($fc, $iv_size);
            $ekey = hash_pbkdf2("sha256", $password, $esalt, $it = 1000, self::key_size(), $raw = true);
            $opts = array('mode' => 'cbc', 'iv' => $iv, 'key' => $ekey);
            stream_filter_append($fc, 'mdecrypt.rijndael-128', STREAM_FILTER_READ, $opts);

            while (!feof($fc)) {
                $block = fread($fc, 8192);

                if (feof($fc)) {
                    $padding = ord($block[strlen($block) - 1]); //assume PKCS7 padding
                    $block = substr($block, 0, 0 - $padding);
                }

                fwrite($fout, $block);
            }

            fclose($fout);
            fclose($fc);
        }
    }

    private static function hash_equals($str1, $str2)
    {
        if (strlen($str1) == strlen($str2)) {
            $res = $str1 ^ $str2;
            for ($ret = 0, $i = strlen($res) - 1; $i >= 0; $i--) $ret |= ord($res[$i]);
            return !$ret;
        }

        return false;
    }

    private static function calculate_hmac_after_32bytes($password, $hsalt, $filename)
    {
        static $init = 0;
        $init or $init = stream_filter_register("user-filter.skipfirst32bytes", "FileSkip32Bytes");
        $stream = 'php://filter/read=user-filter.skipfirst32bytes/resource=' . $filename;
        $hkey = hash_pbkdf2("sha256", $password, $hsalt, $iterations = 1000, 24, $raw = true);

        return hash_hmac_file('sha256', $stream, $hkey, $raw = true);
    }
}

class FileSkip32Bytes extends php_user_filter
{
    private $skipped = 0;

    function filter($in, $out, &$consumed, $closing)
    {
        while ($bucket = stream_bucket_make_writeable($in)) {
            $outlen = $bucket->datalen;

            if ($this->skipped < 32) {
                $outlen = min($bucket->datalen, 32 - $this->skipped);
                $bucket->data = substr($bucket->data, $outlen);
                $bucket->datalen = $bucket->datalen - $outlen;
                $this->skipped += $outlen;
            }

            $consumed += $outlen;
            stream_bucket_append($out, $bucket);
        }

        return PSFS_PASS_ON;
    }
}

class AES_128_CBC extends AES_CBC
{
    protected static function key_size()
    {
        return self::$KEY_SIZES['AES-128'];
    }
}

class AES_192_CBC extends AES_CBC
{
    protected static function key_size()
    {
        return self::$KEY_SIZES['AES-192'];
    }
}

class AES_256_CBC extends AES_CBC
{
    protected static function key_size()
    {
        return self::$KEY_SIZES['AES-256'];
    }
}