The security of APK has been taken as a very serious problem for us. That’s why we will make sure that any APK is from its official manufacture. We use “Certificate Fingerprint” to check who published the APK file. After extracted one string from APK file as the identification of APK certificate (using SHA1 algorithm), we’ll compare this identification with the one existed in Google Play. If they are identical, we‘ll consider this APK is safe. Otherwise, it’s not.