title: iPhone AES encryption issue
body: <p>I use following code to encrypt using AES.</p>
  
  <pre><code>- (NSData*)AES256EncryptWithKey:(NSString*)key theMsg:(NSData *)myMessage {
  
      // 'key' should be 32 bytes for AES256, will be null-padded otherwise
      char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused)
      bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
  
      // fetch key data
      [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
  
      NSUInteger dataLength = [myMessage length];
  
      //See the doc: For block ciphers, the output size will always be less than or
      //equal to the input size plus the size of one block.
      //That's why we need to add the size of one block here
      size_t bufferSize           = dataLength + kCCBlockSizeAES128;
      void* buffer                = malloc(bufferSize);
  
      size_t numBytesEncrypted    = 0;
      CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                            keyPtr, kCCKeySizeAES256,
                                            NULL /* initialization vector (optional) */,
                                            [myMessage bytes], dataLength, /* input */
                                            buffer, bufferSize, /* output */
                                            &amp;numBytesEncrypted);
  
      if (cryptStatus == kCCSuccess)
      {
          //the returned NSData takes ownership of the buffer and will free it on deallocation
          return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
      }
  
      free(buffer); //free the buffer;
      return nil;
  }
  </code></pre>
  
  <p>However the following code chunk returns null if I tried to print the encryptmessage variable. Same thing applies to decryption as well. What am I doing wrong here?</p>
  
  <pre><code> NSData *encrData = [self AES256EncryptWithKey:theKey theMsg:myMessage];
   NSString *encryptmessage = [[NSString alloc] initWithData:encrData encoding:NSUTF8StringEncoding];
  </code></pre>
  
  <p>Thank you</p>