젤리빈부터는  유료앱 설치지 encryption을 해서 기기에 설치된다고 합니다.


구글에서는 :

App encryption: From Jelly Bean and forward, paid apps in Google Play are encrypted with a device-specific key before they are delivered and stored on the device. We know you work hard building your apps. We work hard to protect your investment.



원리는 


When you purchase an app your phone generates an encrypted token so that every time you launch the app if that same token value is not present it knows that it's not on the phone that made the original purchase. No more "sharing" apk's. BlackBerry has been using this for years.