title: How to upload files to Amazon S3 using Android SDK without exposing secret key
body: <p>In this tutorial: <a href="http://aws.amazon.com/articles/3002109349624271" rel="nofollow">http://aws.amazon.com/articles/3002109349624271</a> secret key is used during file upload.</p>
  
  <p>I can't use secret key since my app users don't have amazon account and I can't share my amazon secret key to my app users.</p>
  
  <p>I want to let users upload their avatars directly to S3 without passing through own proxy that has secret key.</p>
  
  <p>I know that this is somehow possible for HTML 5 apps, but haven't find a documentated way for native SDK.</p>