Carleton University
Technical Report TR-13-03
August 9, 2013
Baton: Key Agility for Android without a Centralized Certificate Infrastructure
Abstract
Android’s trust-on-first-use application signing model associates developers with a fixed signing key, but lacks a mechanism to transparently update the key or renew their signing certificate. As an advantage, this feature allows application updates to be recognized as authorized by a party with access to the original signing key. Changing keys or certificates requires that end-users manually uninstall/reinstall apps, losing all non-backed up user data. In this paper, we show that with appropriate OS support, developers can securely and without user intervention transfer signing authority to a new signing key. Our proposal, Baton, modifies Android’s app installation framework enabling key agility while preserving backwards compatibility with current apps and current Android releases. Baton is designed to work consistently with current UID sharing and signature permission requirements. We discuss the technical changes made to Android, and remaining open issues such as key loss and signing authority revocation on Android.