How to create two way encode/decode methods using use-specific key - PHP?

Question

I need two functions/methods, one to encode, one to decode. This is not for storing passwords. Each user will have a specific key/salt to encode the data.

This is how I would like it to work:

function encode($str, $key) {
    // something fancy
}

function decode($str, $key) {
    // something fancy
}

$key = $logged_in_user->get_key();
$plain = 'abc abc 123 123';
$encoded_data = encode($plain, $key);
// some_fancy_encrypted_data_that_is_really_cooooool
$decoded_data = decode($encoded_data, $key);
// abc abc 123 123

Another thing is that every time I use this function it needs to return the same thing every time I use the encode function with the same user key.

How would I do this??

So have you looked at mcrypt (http://www.php.net/manual/en/mcrypt.examples.php) at all? And drop the `hash` tag, because you say you __don't__ want a hash — Mark Baker, Apr 08 '13 at 16:27
I have a [small class](http://stackoverflow.com/questions/15034368/cannot-decrypt-openssl-encrypt-output-on-command-line) that can do what you need, but the real question is why you feel the need to individually encrypt each user's data independently. It is generally assumed that once an attacked can see your stored data they can also see your source code which invalidates most uses of internal encryption, as well-intentioned as they might be. — Sammitch, Apr 08 '13 at 16:37
@Sammitch In some cases it's useful if the key used to encrypt/decrypt the data cannot be found anywhere (and only belongs to the user). I'm pretty sure that LastPass does this as well. — h2ooooooo, Apr 08 '13 at 16:39
@Sammitch Because it is not for the user, but for messages between users. So on the database it is not plain text data. — Jason Silberman, Apr 08 '13 at 16:41
@MarkBaker I have, but even with the same key, every time the output is different. — Jason Silberman, Apr 08 '13 at 16:42

score 48 · Accepted Answer · edited Oct 16 '17 at 04:10

48

$myVarIWantToEncodeAndDecode

Define key (salt, broth etc..): $key = "#&$sdfdfs789fs7d";

To encode:

$encoded = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $myVarIWantToEncodeAndDecode, MCRYPT_MODE_CBC, md5(md5($key))));

To decode:

$decoded = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5($key), base64_decode($encoded), MCRYPT_MODE_CBC, md5(md5($key))), "\0");

Note: mcrypt_decrypt has been DEPRECATED as of PHP 7.1.0. Relying on this function is highly discouraged.

edited Oct 16 '17 at 04:10

Ali Hesari

1,821
5
25
51

answered Apr 08 '13 at 16:43

rinchik

2,642
8
29
46

hmm.. This seems to work, but the data I am getting back from decoding the string is `A”·fµŒ”÷Óÿ‰Zvÿ“õE¥‰¬DõØ&Hå§`. What's wrong? – Jason Silberman Apr 08 '13 at 16:48
So it decodes and encodes right? What are you encoding? plain text? encoded data should look something like this: `VXHE0iM0bMXQecCAKYAzYZjy4gbctqLGQHYvW2cFhaE=` – rinchik Apr 08 '13 at 16:54
I am encoding just "abc abc 123 123" – Jason Silberman Apr 09 '13 at 00:40
Alright fixed it. Now it's working, thanks for the help. @rinchik – Jason Silberman Apr 14 '13 at 16:56
When i run this on foreach loop, only the first iteration works, all the other iteration gives illegal decoded string. – Jagan K Jun 12 '14 at 03:26
@JaganK Post the question with the code sample and link to this comment – rinchik Jun 12 '14 at 19:30
2

Sweet, simple, one liner. Thanks a ton!! Cheers!! +1 :) – Parag Tyagi Jan 19 '15 at 17:23
2

mcrypt_encrypt / _decode are deprecated. Use openssl_encrypt / _decrypt instead. http://php.net/manual/en/function.openssl-encrypt.php – Zbigniew Ledwoń Jun 26 '17 at 09:18

Gowthamraj Vungarala · Answer 2 · 2021-11-18T21:05:08.920

Use openssl_encrypt instead of mcrypt_encrypt

mcrypt_encrypt DEPRECATED as of PHP 7.1.0 and REMOVED as of PHP 7.2.0.

So, Try this..

function encrypt_decrypt($string, $action = 'encrypt')
{
    $encrypt_method = "AES-256-CBC";
    $secret_key = 'AA74CDCC2BBRT935136HH7B63C27'; // user define private key
    $secret_iv = '5fgf5HJ5g27'; // user define secret key
    $key = hash('sha256', $secret_key);
    $iv = substr(hash('sha256', $secret_iv), 0, 16); // sha256 is hash_hmac_algo
    if ($action == 'encrypt') {
        $output = openssl_encrypt($string, $encrypt_method, $key, 0, $iv);
        $output = base64_encode($output);
    } else if ($action == 'decrypt') {
        $output = openssl_decrypt(base64_decode($string), $encrypt_method, $key, 0, $iv);
    }
    return $output;
}
 
echo "Your Encrypted password is = ". $pwd = encrypt_decrypt('spaceo', 'encrypt');
echo "Your Decrypted password is = ". encrypt_decrypt($pwd, 'decrypt');

How to create two way encode/decode methods using use-specific key - PHP?

2 Answers2

Linked