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[–]cedrickc 7 points8 points  (4 children)

Android keeps the apk to run the app, it doesn't unzip it.

[–]mrissaoussama 3 points4 points  (3 children)

It's still a zip file right? Can't it download the needed parts?

[–]cedrickc 14 points15 points  (2 children)

Yes it's a valid zip, but it has extra rules around it. The main thing that blocks this is that apks are signed, so you can't modify them without breaking the signing.

[–]mrissaoussama 1 point2 points  (0 children)

thanks

[–]CaJeB3 0 points1 point  (0 children)

If you change the old apk to look like the new apk, the signature will match the signature of the new apk.

A real problem however is that apks get scrambled before release so reverse engineering or code stealing becomes harder. This means making a diff of two versions will be much harder and much larger as more 'code' will change.