title: Verify Android apk has not been repackaged?
body: <p>Looking to improved the security of my Android app to flag if the .apk has been extracted, modified, repacked and resigned. Here's article from Zdnet noting the issue <a href="http://www.zdnet.com/android-malwares-dirty-secret-repackaging-of-legit-apps-7000000886/">link1</a>. </p>
  
  <p>The concern is if the app is targeted by hackers they could add malicious code and upload to an alternate app store and dupe users in to downloading it. </p>
  
  <p>So I'm thinking code to verify a checksum of the apk or signing certificate?</p>
  
  <p>I appreciate the app code could be repacked and any security code removed, but it does increase the difficulty of repacking it, maybe enough for them to try another app.</p>
  
  <p>[update]I know the Google Play store licensing module offers something similar but I'm looking for something for non paid apps and other/non marketplaces. </p>