Fork of Example https://paragonie.com/blog/2015/05/using-encryption-and-authentication-correctly in defuse/php-encryption

gistfile1.php

<?php
require_once('Crypto.php');
function setKey(){
	try {
		$key = Crypto::CreateNewRandomKey();
		// WARNING: Do NOT encode $key with bin2hex() or base64_encode(),
		// they may leak the key to the attacker through side channels.
	} catch (CryptoTestFailedException $ex) {
		die('Cannot safely create a key');
	} catch (CannotPerformOperationException $ex) {
		die('Cannot safely create a key');
	}
return $key;
}

/**
 * Store ciphertext in a cookie
 * 
 * @param string $name - cookie name
 * @param mixed $cookieData - cookie data
 * @param string $key - crypto key
 */
 

function setSafeCookie($name, $cookieData, $key){
  try {
      $ciphertext = Crypto::Encrypt(json_encode($cookieData), $key);
  } catch (CryptoTestFailedException $ex) {
      die('Cannot safely perform encryption');
  } catch (CannotPerformOperationException $ex) {
      die('Cannot safely perform decryption');
  }
    
return setcookie($name, $ciphertext);
}



/**
 * Decrypt a cookie, expand to array
 * 
 * @param string $name - cookie name
 * @param string $key - crypto key
 */
function getSafeCookie($name, $key){
	if (!isset($_COOKIE[$name])) {
		  return array();
	}

	$ciphertext = $_COOKIE[$name];
		
	try {
		 $decrypted = Crypto::Decrypt($ciphertext, $key);
	} catch (InvalidCiphertextException $ex) { // VERY IMPORTANT
		  // Either:
		  //   1. The ciphertext was modified by the attacker,
		  //   2. The key is wrong, or
		  //   3. $ciphertext is not a valid ciphertext or was corrupted.
		  // Assume the worst.
		  die('DANGER! DANGER! The ciphertext has been tampered with!');
	} catch (CryptoTestFailedException $ex) {
		  die('Cannot safely perform encryption');
	} catch (CannotPerformOperationException $ex) {
		  die('Cannot safely perform decryption');
	}

	if (empty($decrypted)) {
			array();
	}
    
return json_decode($decrypted, true);
}

I've dowloaded the .zip of 'defuse/php-encryption' and installed it (one week ago).

I just tried your script and I have this error :
Fatal error: Class 'Crypto' not found in /home/zideesdubj/www/_tests2enfants/_test_session/php-encryption-master/test.php on line XXX

Could you please help me ?

You need https://github.com/defuse/php-encryption