title: Custom permission between two apps with different signatures
body: <p>I have two application which are signed with different certs/keys.</p>
  
  <p>I want to make <strong>authenticated</strong> call (to a service) from application A to app B (so no 3rd party can make such call).</p>
  
  <p>Common solution for such things in Android is custom permissions with signature protection level. However, it won't work in my case, because two apps are signed with different certs (developed by different companies)</p>
  
  <p>So, the question is. What is the best practice for this case, if I want allow only application A (or any apps developed by this company) to call/bind a service in app B?</p>