title: When is the Android APK signature verified?
body: <p>Under which circumstances is the APK signature (contained in /META-INF/CERT.*) verified? </p>
  
  <p>I image the following situations:</p>
  
  <ol>
  <li>During installation from Google Play.</li>
  <li>During installation from adb install.</li>
  <li>Others?</li>
  </ol>
  
  <p>I am interesting in the actual signature, not only the check of the various digests contained in the files /META-INF/MANIFEST.MF and /META-INF/CERT.SF.</p>