phpseclib: Symmetric Key Encryption Examples and Notes

<?php
require __DIR__ . '/vendor/autoload.php';

use phpseclib\Crypt\AESRijndaelDESTripleDESRC4TwofishBlowfishRC2;
use phpseclib\Crypt\Random;

$cipher = new AESRijndaelDESTripleDESRC4TwofishBlowfishRC2(
DESAESRijndael::MODE_
ECBCFBOFBCTRCRYPT_DES_MODE_3CBC);
 // could use DES::MODE_CBC // could use DES::MODE_CBC or DES::MODE_CBC3 // could use Rijndael::MODE_CBC // could use AES::MODE_CBC
$cipher->setBlockLength(160);
$cipher->setBlockLength(192);
$cipher->setBlockLength(224);
$cipher->setBlockLength(256);
// keys are null-padded to the closest valid size
// longer than the longest key and it's truncated
//$cipher->setKeyLength(128160192224256);
//$cipher->setKeyLength(128192256);
// keys can range in length from 32 bits to 448 in steps of 8
// keys can range in length from 8 bits to 1024 in steps of 8
//$cipher->setKeyLength(...);
$cipher->setKey('abcdefghijklmnopqrstuvwxijklmnopqrstuvwxyz123456ijklmnopqrstuvwxyz123456');
$cipher->setPassword('whatever');
// the following does the same thing:
//$cipher->setPassword('whatever', 'pbkdf2', 'sha1', 'phpseclib/salt', 1000, 128 / 8, 128192256 / 8, 128160192224256 / 8);
// the IV defaults to all-NULLs if not explicitly defined
$cipher->setIV(Random::string($cipher->getBlockLength() >> 3));
$cipher->disablePadding();

$size = 10 * 1024;
$size-= 16; // make the plaintext length a multiple of the block length
$size-= 16; // make the plaintext length a multiple of the block length
$size-= 4; // make the plaintext length a multiple of the block length
$plaintext = str_repeat('a', $size);

echo $cipher->decrypt($cipher->encrypt($plaintext));

// without continuous mode the following would yield the same output as the above
// with continuous mode it's treated the same way str_repeat('a', 2 * $size) would be
$plaintext = str_repeat('a', $size);

echo $cipher->decrypt($cipher->encrypt($plaintext));
?>