Encryption in JavaScript and decryption with PHP - Stack Overflow

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I'm encrypting my user password in JavaScript like this:

 var encryptedPassword = CryptoJS.AES.encrypt(password, "Secret Passphrase");

It works fine but now I'm trying to decrypt in PHP on the server side like this:

 $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_RAND);
 $decryptPassword = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, "Secret Passphrase", base64_decode($password), MCRYPT_MODE_CBC, $iv);

it doesn't works at all, the decrypted password string looks very strange:

 string(64) ">�OX2MS��댗v�<$�ʕ��i�̄��_��P���\�կ=�_6(�m����,4WT7��a"

Here is the current state of my code in JavaScript after the helpful comments:

    var encryptedPassword = CryptoJS.AES.encrypt(password, "Secret Passphrase");
    var ivHex = encryptedPassword.iv.toString();
    var ivSize = encryptedPassword.algorithm.ivSize; // same as blockSize
    var keySize = encryptedPassword.algorithm.keySize;
    var keyHex = encryptedPassword.key.toString();
    var saltHex = encryptedPassword.salt.toString(); // must be sent
    var openSslFormattedCipherTextString = encryptedPassword.toString(); // not used
    var cipherTextHex = encryptedPassword.ciphertext.toString(); // must be sent

I am sending saltHex and CipherTextHex to the PHP server and I'm using mcrypt_decrypt() like this:

 $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), $saltHex);
 $decryptPassword = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, "Secret Passphrase", base64_decode($cipherTextHex), MCRYPT_MODE_CBC, $iv);

It still does't work with this updated code.

Can someone help me to decrypt properly with mcrypt_decrypt() PHP function for a simple AES encryption method ? I'm sure I am doing something wrong with the cipher, mcrypt mode and the IV parameters inside my mcrypt_decrypt() method. Thanks if you know.

I'm encrypting my user password in JavaScript like this:

 var encryptedPassword = CryptoJS.AES.encrypt(password, "Secret Passphrase");

It works fine but now I'm trying to decrypt in PHP on the server side like this:

 $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_RAND);
 $decryptPassword = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, "Secret Passphrase", base64_decode($password), MCRYPT_MODE_CBC, $iv);

it doesn't works at all, the decrypted password string looks very strange:

 string(64) ">�OX2MS��댗v�<$�ʕ��i�̄��_��P���\�կ=�_6(�m����,4WT7��a"

Here is the current state of my code in JavaScript after the helpful comments:

    var encryptedPassword = CryptoJS.AES.encrypt(password, "Secret Passphrase");
    var ivHex = encryptedPassword.iv.toString();
    var ivSize = encryptedPassword.algorithm.ivSize; // same as blockSize
    var keySize = encryptedPassword.algorithm.keySize;
    var keyHex = encryptedPassword.key.toString();
    var saltHex = encryptedPassword.salt.toString(); // must be sent
    var openSslFormattedCipherTextString = encryptedPassword.toString(); // not used
    var cipherTextHex = encryptedPassword.ciphertext.toString(); // must be sent

I am sending saltHex and CipherTextHex to the PHP server and I'm using mcrypt_decrypt() like this:

 $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), $saltHex);
 $decryptPassword = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, "Secret Passphrase", base64_decode($cipherTextHex), MCRYPT_MODE_CBC, $iv);

It still does't work with this updated code.

Can someone help me to decrypt properly with mcrypt_decrypt() PHP function for a simple AES encryption method ? I'm sure I am doing something wrong with the cipher, mcrypt mode and the IV parameters inside my mcrypt_decrypt() method. Thanks if you know.

• javascript
• php
• encryption
• mcrypt
• cryptojs

Share Improve this question Follow edited Dec 28, 2014 at 15:11 Nizar B. asked Dec 28, 2014 at 14:17 Nizar B.Nizar B. 3,11899 gold badges4141 silver badges5656 bronze badges 12

• @ArtjomB. Can you please, give more precision ? – Nizar B. Commented Dec 28, 2014 at 14:21
• What's advantage of encrypting in JavaScript and decrypt in PHP, Because you can do encrypt and decrypt in PHP – user4314601 Commented Dec 28, 2014 at 14:21
• @lawrenceoverflow The encryption in the client side with JavaScript is used to not POST the login form in clear plain text to my PHP server. – Nizar B. Commented Dec 28, 2014 at 14:22
• 1 See here: stackoverflow.com/a/27250883/1816580 and convert the code to php if you want – Artjom B. Commented Dec 28, 2014 at 14:24
• 1 If you don't have the IV and salt then you're out of luck. You didn't show how encryptedPassword is transmitted, because it may be encoded ito it. CryptoJS uses an OpenSSLFormatter. You should look into the code of CryptoJS. – Artjom B. Commented Dec 28, 2014 at 14:32

 |  Show 7 more comments

3 Answers 3

Sorted by: Reset to default 18

The problem is that in the CryptoJS code a password is used to derive the key and the IV to be used for AES encryption, but mcrypt only uses the key to encrypt/decrypt. This information needs to be passed to php. Since you don't want to transmit the password, you have to derive the key and IV in the same way in php.

The following code derives the key and IV from a password and salt. It is modeled after the code in my answer here (for more information).

function evpKDF($password, $salt, $keySize = 8, $ivSize = 4, $iterations = 1, $hashAlgorithm = "md5") {
    $targetKeySize = $keySize + $ivSize;
    $derivedBytes = "";
    $numberOfDerivedWords = 0;
    $block = NULL;
    $hasher = hash_init($hashAlgorithm);
    while ($numberOfDerivedWords < $targetKeySize) {
        if ($block != NULL) {
            hash_update($hasher, $block);
        }
        hash_update($hasher, $password);
        hash_update($hasher, $salt);
        $block = hash_final($hasher, TRUE);
        $hasher = hash_init($hashAlgorithm);

        // Iterations
        for ($i = 1; $i < $iterations; $i++) {
            hash_update($hasher, $block);
            $block = hash_final($hasher, TRUE);
            $hasher = hash_init($hashAlgorithm);
        }

        $derivedBytes .= substr($block, 0, min(strlen($block), ($targetKeySize - $numberOfDerivedWords) * 4));

        $numberOfDerivedWords += strlen($block)/4;
    }

    return array(
        "key" => substr($derivedBytes, 0, $keySize * 4),
        "iv"  => substr($derivedBytes, $keySize * 4, $ivSize * 4)
    );
}

The salt is generated during encryption in CryptoJS and needs to be sent to php with the ciphertext. Before invoking evpKDF the salt has to be converted to a binary string from hex.

$keyAndIV = evpKDF("Secret Passphrase", hex2bin($saltHex));
$decryptPassword = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, 
        $keyAndIV["key"], 
        hex2bin($cipherTextHex), 
        MCRYPT_MODE_CBC, 
        $keyAndIV["iv"]);

---

If only encryptedPassword.toString() was sent to the server, then it is necessary to split the salt and actual ciphertext before use. The format is a proprietary OpenSSL-compatible format with the first 8 bytes being "Salted__", the next 8 bytes being the random salt and the rest is the actual ciphertext. Everything together is Base64-encoded.

function decrypt($ciphertext, $password) {
    $ciphertext = base64_decode($ciphertext);
    if (substr($ciphertext, 0, 8) != "Salted__") {
        return false;
    }
    $salt = substr($ciphertext, 8, 8);
    $keyAndIV = evpKDF($password, $salt);
    $decryptPassword = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, 
            $keyAndIV["key"], 
            substr($ciphertext, 16), 
            MCRYPT_MODE_CBC, 
            $keyAndIV["iv"]);

    // unpad (PKCS#7)
    return substr($decryptPassword, 0, strlen($decryptPassword) - ord($decryptPassword[strlen($decryptPassword)-1]));
}

The same can be achieved with the OpenSSL extension instead of Mcrypt:

function decrypt($ciphertext, $password) {
    $ciphertext = base64_decode($ciphertext);
    if (substr($ciphertext, 0, 8) != "Salted__") {
        return false;
    }
    $salt = substr($ciphertext, 8, 8);
    $keyAndIV = evpKDF($password, $salt);
    $decryptPassword = openssl_decrypt(
            substr($ciphertext, 16), 
            "aes-256-cbc",
            $keyAndIV["key"], 
            OPENSSL_RAW_DATA, // base64 was already decoded
            $keyAndIV["iv"]);

    return $decryptPassword;
}

/** 
 *-------------PHP code example-----------------
 */
/**
 * Decrypt data from a CryptoJS json encoding string
 *
 * @param mixed $passphrase
 * @param mixed $jsonString
 * @return mixed
 */
function cryptoJsAesDecrypt($passphrase, $jsonString){
    $jsondata = json_decode($jsonString, true);
    $salt = hex2bin($jsondata["s"]);
    $ct = base64_decode($jsondata["ct"]);
    $iv  = hex2bin($jsondata["iv"]);
    $concatedPassphrase = $passphrase.$salt;
    $md5 = array();
    $md5[0] = md5($concatedPassphrase, true);
    $result = $md5[0];
    for ($i = 1; $i < 3; $i++) {
        $md5[$i] = md5($md5[$i - 1].$concatedPassphrase, true);
        $result .= $md5[$i];
    }
    $key = substr($result, 0, 32);
    $data = openssl_decrypt($ct, 'aes-256-cbc', $key, true, $iv);
    return json_decode($data, true);
}

/**
 * Encrypt value to a cryptojs compatiable json encoding string
 *
 * @param mixed $passphrase
 * @param mixed $value
 * @return string
 */
function cryptoJsAesEncrypt($passphrase, $value){
    $salt = openssl_random_pseudo_bytes(8);
    $salted = '';
    $dx = '';
    while (strlen($salted) < 48) {
        $dx = md5($dx.$passphrase.$salt, true);
        $salted .= $dx;
    }
    $key = substr($salted, 0, 32);
    $iv  = substr($salted, 32,16);
    $encrypted_data = openssl_encrypt(json_encode($value), 'aes-256-cbc', $key, true, $iv);
    $data = array("ct" => base64_encode($encrypted_data), "iv" => bin2hex($iv), "s" => bin2hex($salt));
    return json_encode($data);
}
$encrypted = '{"ct":"nPfd1U0y9o2hRCdwJK6XkM1E01wa1ZjMu3eAzGjUD60=","iv":"2abda27fc571cf74e6efc1ba564801f9","s":"813a340e805f54ae"}';
$key = "123456";
$decrypted = cryptoJsAesDecrypt($key, $encrypted);

/* -------------Javascript code example-----------------*/
var CryptoJSAesJson = {
    stringify: function (cipherParams) {
        var j = {ct: cipherParams.ciphertext.toString(CryptoJS.enc.Base64)};
        if (cipherParams.iv) j.iv = cipherParams.iv.toString();
        if (cipherParams.salt) j.s = cipherParams.salt.toString();
        return JSON.stringify(j);
    },
    parse: function (jsonStr) {
        var j = JSON.parse(jsonStr);
        var cipherParams = CryptoJS.lib.CipherParams.create({ciphertext: CryptoJS.enc.Base64.parse(j.ct)});
        if (j.iv) cipherParams.iv = CryptoJS.enc.Hex.parse(j.iv)
        if (j.s) cipherParams.salt = CryptoJS.enc.Hex.parse(j.s)
        return cipherParams;
    }
}
var key = "123456";
var encrypted = CryptoJS.AES.encrypt(JSON.stringify("value to encrypt"), key, {format: CryptoJSAesJson}).toString();
console.log(encrypted);
var decrypted = JSON.parse(CryptoJS.AES.decrypt(encrypted, key, {format: CryptoJSAesJson}).toString(CryptoJS.enc.Utf8));
console.log("decryyepted: "+decrypted);

<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/4.0.0/crypto-js.min.js"></script>

You can't decrypt with a random initialisation vector - you need to use the same IV the data was encrypted with. Also, IIRC, AES defaults to an 8 bit representation of the encrypted data which will need to be handled carefully in transfer over HTTP.

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