title: Error "Reverse auth credentials are invalid" on Twitter Reverse Auth
body: <p>I am trying to implement Reverse Auth in an iOS PhoneGap / Cordova application.</p>
  
  <p>I have Step 1 working correctly - my server performs a Token Request and returns the OAuth-Header-Like response to the mobile application.</p>
  
  <p>But Step 2 isn't working.  The response from Step 1 is sent to "/oauth/access_token" but I receive the response:
  Reverse auth credentials are invalid</p>
  
  <p>Here is what my Step 1 response looks like:</p>
  
  <pre><code>OAuth oauth_token="xxx", oauth_timestamp="1361189727", oauth_nonce="QoUtVy4wchGbrSg7biruOIqsTU7G5gZHix9K7a5yU0", oauth_signature_method="HMAC-SHA1", oauth_signature="qcCuBxaYFJRVi0C1rpuqygSg6Bs%3D", oauth_consumer_key="xxx", oauth_version="1.0"
  </code></pre>
  
  <p>Here is what my Step 2 code is:</p>
  
  <pre><code>NSDictionary *step2Params = [[NSMutableDictionary alloc] init];
  [step2Params setValue:TW_CONSUMER_KEY forKey:@"x_reverse_auth_target"];
  [step2Params setValue:step1ResponseString:@"x_reverse_auth_parameters"];
  NSURL *authTokenURL = [NSURL URLWithString:TW_OAUTH_URL_AUTH_TOKEN];
  id&lt;GenericTwitterRequest&gt; step2Request =
  [self requestWithUrl:authTokenURL
            parameters:step2Params
         requestMethod:SLRequestMethodPOST];
  [step2Request setAccount:selectedTwitterAccount];
  [step2Request performRequestWithHandler:^(NSData *responseData, NSURLResponse *urlResponse, NSError *step2error)
  </code></pre>
  
  <p>I am using this plugin to handle the Reverse Auth calls:
  <a href="https://github.com/PatrickHeneise/SocialAuthenticationPlugin/blob/master/iOS/SocialAuthenticationPlugin.m" rel="nofollow">https://github.com/PatrickHeneise/SocialAuthenticationPlugin/blob/master/iOS/SocialAuthenticationPlugin.m</a></p>
  
  <p>Any help on what is going wrong?  </p>
  
  <p>The Step 1 response is in the form described in the docs ("oauth header like") and Step 2 just passes that exact string to Twitter along with my consumer key.  What am I missing?</p>