allow invalid certificates with AFNetworking

I have been using following code

AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];
operation.allowsInvalidSSLCertificate=YES;

Now i have changed AFNetworking to latest version that is 2.0. operation.allowsInvalidSSLCertificate is not working anymore with AFHTTPRequestOperation. As per documents i used

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
manager.securityPolicy.allowInvalidCertificates = YES;

and my request code is

AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];

[operation  setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {

    NSLog (@"success: %@", operation.responseString);

}
                                  failure:^(AFHTTPRequestOperation *operation, NSError *error) {
                                      NSLog(@"error: %@",  error.description);
                                  }
 ];

[operation start];
[operation waitUntilFinished];

But this is not working for HTTPS which require certificates. What should i do to make this work?