encryption.php

<?php
/**
 * Encryption class for encrypt/decrypt that works between programming languages.
 *
 * @author Vee Winch.
 * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
 */
class Encryption
{
  /**
   * @link http://php.net/manual/en/function.openssl-get-cipher-methods.php Available methods.
   * @var string Cipher method. Recommended AES-128-CBC, AES-192-CBC, AES-256-CBC
   */
  protected $encryptMethod = 'AES-256-CBC';
  /**
   * Decrypt string.
   *
   * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
   * @param string $encryptedString The encrypted string that is base64 encode.
   * @param string $key The key.
   * @return mixed Return original string value.
   */
  public function decrypt($encryptedString, $key)
  {
    $json = json_decode(base64_decode($encryptedString), true);
    try {
      $salt = hex2bin($json["salt"]);
      $iv = hex2bin($json["iv"]);
    } catch (Exception $e) {
      return null;
    }
    $cipherText = base64_decode($json['ciphertext']);
    $iterations = intval(abs($json['iterations']));
    if ($iterations <= 0) {
      $iterations = 999;
    }
    $hashKey = hash_pbkdf2('sha512', $key, $salt, $iterations, ($this->encryptMethodLength() / 4));
    unset($iterations, $json, $salt);
    $decrypted= openssl_decrypt($cipherText , $this->encryptMethod, hex2bin($hashKey), OPENSSL_RAW_DATA, $iv);
    unset($cipherText, $hashKey, $iv);
    return $decrypted;
  }// decrypt
  /**
   * Encrypt string.
   *
   * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
   * @param string $string The original string to be encrypt.
   * @param string $key The key.
   * @return string Return encrypted string.
   */
  public function encrypt($string, $key)
  {
    $ivLength = openssl_cipher_iv_length($this->encryptMethod);
    $iv = openssl_random_pseudo_bytes($ivLength);

    $salt = openssl_random_pseudo_bytes(256);
    $iterations = 999;
    $hashKey = hash_pbkdf2('sha512', $key, $salt, $iterations, ($this->encryptMethodLength() / 4));
    $encryptedString = openssl_encrypt($string, $this->encryptMethod, hex2bin($hashKey), OPENSSL_RAW_DATA, $iv);
    $encryptedString = base64_encode($encryptedString);
    unset($hashKey);
    $output = ['ciphertext' => $encryptedString, 'iv' => bin2hex($iv), 'salt' => bin2hex($salt), 'iterations' => $iterations];
    unset($encryptedString, $iterations, $iv, $ivLength, $salt);
    return base64_encode(json_encode($output));
  }// encrypt
  /**
   * Get encrypt method length number (128, 192, 256).
   *
   * @return integer.
   */
  protected function encryptMethodLength() {
    $number = filter_var($this->encryptMethod, FILTER_SANITIZE_NUMBER_INT);
    return intval(abs($number));
  }// encryptMethodLength
  /**
   * Set encryption method.
   *
   * @link http://php.net/manual/en/function.openssl-get-cipher-methods.php Available methods.
   * @param string $cipherMethod
   */
  public function setCipherMethod($cipherMethod)
  {
    $this->encryptMethod = $cipherMethod;
  }// setCipherMethod
}