Question

I would like to save data in cookies (user name, email address, etc…) but I don’t the user to easily read it or modify it. I need to be able able to read the data back. How can I do that with php 5.2+?

It would be used for ‘welcome back bob’ kind of feature. It is not a replacement for persistence or session storage.

Answer 1

We use mcrypt in our projects to achieve encryption. Below is a code sample based on content found on the internet:

<?php class MyProjCrypt {      private $td;     private $iv;     private $ks;     private $salt;     private $encStr;     private $decStr;       /**      *  The constructor initializes the cryptography library      * @param $salt string The encryption key      * @return void      */     function __construct($salt) {         $this->td = mcrypt_module_open('rijndael-256', '', 'ofb', ''); // algorithm         $this->ks = mcrypt_enc_get_key_size($this->td); // key size needed for the algorithm         $this->salt = substr(md5($salt), 0, $this->ks);     }      /**      * Generates a hex string of $src      * @param $src string String to be encrypted      * @return void      */     function encrypt($src) {         srand(( double) microtime() * 1000000); //for sake of MCRYPT_RAND         $this->iv = mcrypt_create_iv($this->ks, MCRYPT_RAND);          mcrypt_generic_init($this->td, $this->salt, $this->iv);         $tmpStr = mcrypt_generic($this->td, $src);         mcrypt_generic_deinit($this->td);         mcrypt_module_close($this->td);          //convert the encrypted binary string to hex         //$this->iv is needed to decrypt the string later. It has a fixed length and can easily          //be seperated out from the encrypted String         $this->encStr = bin2hex($this->iv.$tmpStr);      }      /**      * Decrypts a hex string          * @param $src string String to be decrypted      * @return void      */     function decrypt($src) {         //convert the hex string to binary         $corrected = preg_replace('[^0-9a-fA-F]', '', $src);         $binenc = pack('H'.strlen($corrected), $corrected);          //retrieve the iv from the encrypted string         $this->iv = substr($binenc, 0, $this->ks);          //retrieve the encrypted string alone(minus iv)         $binstr = substr($binenc, $this->ks);          /* Initialize encryption module for decryption */         mcrypt_generic_init($this->td, $this->salt, $this->iv);         /* Decrypt encrypted string */         $decrypted = mdecrypt_generic($this->td, $binstr);          /* Terminate decryption handle and close module */         mcrypt_generic_deinit($this->td);         mcrypt_module_close($this->td);         $this->decStr = trim($decrypted);      } }