title: Different facebook apps are using the same key hash
body: <p>The <a href="http://developer.android.com/tools/publishing/app-signing.html#strategies" rel="nofollow">Android developer documentation</a> contains the following advise on Signing an application:</p>
  
  <p>"In general, the recommended strategy for all developers is to sign all of your applications with the same certificate, throughout the expected lifespan of your applications."</p>
  
  <p>At my company, We generally follow this advise, but regarding linked facebook apps I have some concerns. 
  As far as I know, if you want to link a native android app and a facebook app together, you have to generate a key hash based on the signature used for android application release.
  My question is that, is it correct to use the same signature for linking 2 different facebook applications? For example: 'A' android app is linked with 'A' facebook app, and 'B' android app is linked with 'B' facebook app. Both 'A' and 'B' android apps are signed with the same certificate. 
  Is the generated key hash used on the facebook side as a primary key or as just another level of security check? </p>