Result null when convert nsstring to nsdictionary
<p>I have encrypted string from server like this :</p>

<blockquote>
  <p>4gtFiu1DVK2MKGHcFtbuR4spdrhAixptPH0wz2n2VlawBWKlDE/I9m1K4GsBdBH8MJuzhiVHvQy0PYvvcCWuQv6dE1OHzflW3mN3jbEVLrodXvZVnafyo8Lmn6i2x4gGh3XB+ij59FvOOklM+D3E5mhwIFO0cZxGE0eAx2Gn9tj1euoMIChLhnD/FtvuKoucQBCKTTBfihu7dVdZ+gLxqsmusZqUeHnIYYrg3kpH2gu0wQ2GiKm/UMoogYR0JRoYac5ui/aVeDWS14bLoqAc4vJVWVt+vJhJG+a8rC5B68raUDaxhhCJM0b6lpOqAJ/5iVZKLufYMLv2FMNoc5LFkP5QNAYneYCkhfWfNzcDgYC0biYQsT1uIfSgN2q86Qdghe9OBMBFfisfaEsg8+qI7JxhNh+eA6tU5W/yJTIckhvk=</p>
</blockquote>

<p>This is my code to decrypt that encrypted string :</p>

<pre><code>- (NSString *)decryptAES:(NSString *)text {
NSDictionary *keyDict = [self chooseKey:text];
NSString *key = [keyDict objectForKey:@"key"];
NSData *keyHash = [[key dataUsingEncoding:NSUTF8StringEncoding] SHA256Hash];

NSString *newText = [text stringByReplacingCharactersInRange:NSMakeRange(1, 1) withString:@""];
NSData *encryptData = [NSData base64DataFromString:newText];
NSData *plainData = [encryptData AES256Decrypt:keyHash];
NSString *plain = [[NSString alloc] initWithData:plainData encoding:NSUTF8StringEncoding];

return plain;
}
</code></pre>

<p>I have successfully decrypted that encrypted string into NSString and the result is:</p>

<pre><code>{
    "promo": [{
        "status": 1,
        "link": "https://www.s6pay.com/asset_template/img/promo/sspquizpromo.jpg",
        "description": "SSP mengadakan quiz yang berhadiah tiket kereta api dengan menjawab kuis.",
        "promoMessage": "Success",
        "promoTitle": "SSP Promo Quiz! Bagi-bagi Tiket Kereta Api"
    }],
    "count": 1
}
</code></pre>

<p>I want to convert that decrypt string into NSDictionary/json, my code like this :</p>

<pre><code>NSMutableString *plainTemp = [NSMutableString stringWithString:[[NSData alloc] decryptAES:jsonMutableString]]
NSLog(@"Decrypt %@",plainTemp);
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:[plainTemp dataUsingEncoding:NSUTF8StringEncoding] options:0 error:nil];
NSLog(@"JSON %@",json);
</code></pre>

<p>I'm trying to change options with NSJSONReadingMutableLeaves, NSJSONReadingAllowFragments or NSJSONReadingMutableContainers but still give result JSON (null).</p>

<p>I'm trying to check that decrypted string using <a href="http://json.parser.online.fr" rel="nofollow">http://json.parser.online.fr</a> (result of encrypted string) and that result is valid JSON.</p>

<p>What is wrong with my code? Can you please help me? Thank you..</p>