title: Use AES to encrypt with Objective-C and decrypt with PHP
body: <p>I want to use AES to encrypt a password in Objective-C, and then decrypt it in PHP, but I have two problems.</p>
  
  <ol>
  <li>I encrypt the password, but it's an <code>NSData</code> object, so I encode it with base64, but when I decode in PHP, the result is <code>nil</code>. So I can't decrypt it.</li>
  <li>I can encrypt and decrypt the password in Objective-C, so it is the PHP that is the problem, but when I encrypt with AES and then encode with base64, the results are not the same.</li>
  </ol>
  
  <p>Here is my code:</p>
  
  <p>PHP:</p>
  
  <pre><code>    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
      $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
      $key = "a16byteslongkey!";
      $plaintext = "iphone";
      $ciphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $plaintext, MCRYPT_MODE_ECB, $iv);
      $ciphertext = base64_encode($ciphertext);
      echo "ciphertext: ".$ciphertext."&lt;br/&gt;";
  
      $ciphertext = base64_decode($ciphertext);
      $plaintext = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $ciphertext, MCRYPT_MODE_ECB, $iv);
      echo "plaintext: ".$plaintext."&lt;br/&gt;";
  </code></pre>
  
  <p>output:</p>
  
  <pre><code>    ciphertext: SXNepKfh0IrlDDdkq4EdmQ==
      plaintext: iphone
  </code></pre>
  
  <p>Objective-C: (Get the full source code here: <a href="https://gist.github.com/838614" rel="nofollow">https://gist.github.com/838614</a>)</p>
  
  <pre><code>    NSString *key = @"a16byteslongkey!";
      NSString *plaintext = @"iphone";
  
      NSString *ciphertext = [plaintext AES256EncryptWithKey: key];
      NSLog(@"ciphertext: %@", ciphertext);
  
      plaintext = [ciphertext AES256DecryptWithKey: key];
      NSLog(@"plaintext: %@", plaintext);
  </code></pre>
  
  <p>output:</p>
  
  <pre><code>    ciphertext: D19l3gsgXJlrLl7B2oCT6g==
      plaintext: iphone
  </code></pre>
  
  <p>i replace kCCKeySizeAES256 with kCCKeySizeAES128, and replace "kCCOptionPKCS7Padding" with "kCCOptionPKCS7Padding | kCCOptionECBMode",</p>