Encrypt with CryptoJS and decrypt with PHP

Question

On the client side (mobile device) I encrypt a users password with CryptoJS:

var lib_crypt = require('aes');

$.loginButton.addEventListener('click', function(e){

var key = lib_crypt.CryptoJS.enc.Hex.parse('bcb04b7e103a0cd8b54763051cef08bc55abe029fdebae5e1d417e2ffb2a00a3');
var iv  = lib_crypt.CryptoJS.enc.Hex.parse('101112131415161718191a1b1c1d1e1f');

var encrypted = lib_crypt.CryptoJS.AES.encrypt($.passwordInput.value, key, { iv: iv });

var password_base64 = encrypted.ciphertext.toString(lib_crypt.CryptoJS.enc.Base64); 
return password_base64; 
});

On the server side i want to decrypt it with mcrypt_decrypt:

function decryptPassword($password)
{
    $key = pack('H*', "bcb04b7e103a0cd8b54763051cef08bc55abe029fdebae5e1d417e2ffb2a00a3");
    $ciphertext_dec = base64_decode($password);
    $iv_dec = "101112131415161718191a1b1c1d1e1f";

    $ciphertext_dec = substr($ciphertext_dec, 16);
    $decryptedPassword = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec);

    return trim($decryptedPassword);
}

I use the same key and IV, what do I do wrong?

Answer 1

Hello,

in order to achieve this it should be considered to use the key and iv with 32 hex digits each, i had to solve exactly this doing my stuff and here is the way it goes

<!--
This reach.your.crypto.js is just a ficticious placeholder, 
that was used replaced by http://crypto-js.googlecode.com/svn/tags/3.1.2/build/,
which does not exist anymore,
which is the path to your CryptoJS library,
that can be downloaded through 
https://code.google.com/archive/p/crypto-js/downloads?page=1
-->
<script src="reach.your.crypto.js/rollups/aes.js">
</script>

<script type="text/javascript">
//The key and iv should be 32 hex digits each, any hex digits you want, 
//but it needs to be 32 on length each
var key = CryptoJS.enc.Hex.parse("0123456789abcdef0123456789abcdef");
var iv =  CryptoJS.enc.Hex.parse("abcdef9876543210abcdef9876543210");

/*
if you wish to have a more friendly key, you can convert letters to Hex this way:
var a = "D";
var hex_D = a.charCodeAt(0).toString(16);
just to mention,
if it were to binary, it would be:
var binary_D = a.charCodeAt(0).toString(2);
*/

var secret = "Hi, this will be seen uncrypted later on";

//crypted
var encrypted = CryptoJS.AES.encrypt(secret, key, {iv:iv});
//and the ciphertext put to base64
encrypted = encrypted.ciphertext.toString(CryptoJS.enc.Base64);    
//Assuming you have control on the server side, and know the key and iv hexes(we do),
//the encrypted var is all you need to pass through ajax,
//Let's follow with welcomed pure JS style, to reinforce one and other concept if needed
var xh = new XMLHttpRequest();
xh.open("POST", "decrypt_in_php.php", true);
xh.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xh.send("encrypted="+encodeURIComponent(encrypted));
</script>

And now receiving and decrypting in PHP

<?php
//Here we have the key and iv which we know, because we have just chosen them on the JS,
//the pack acts just like the parse Hex from JS

$key = pack("H*", "0123456789abcdef0123456789abcdef");
$iv =  pack("H*", "abcdef9876543210abcdef9876543210");

//Now we receive the encrypted from the post, we should decode it from base64,
$encrypted = base64_decode($_POST["encrypted"]);
$shown = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $encrypted, MCRYPT_MODE_CBC, $iv);

echo $shown;
//Although the decrypted is shown, there may be needed to trim and str_replace some \r \n \x06 \x05, if there is not a better "trim" way to do it though
?>

With this we will have back the "Hi, this will be seen uncrypted later on" :)