Maxoid: transparently confining mobile applications with custom views of state

We present Maxoid, a system that allows an Android app to process its sensitive data by securely invoking other, untrusted apps. Maxoid provides secrecy and integrity for both the invoking app and the invoked app. For each app, Maxoid presents custom views of private and public state (files and data in content providers) to transparently redirect unsafe data flows and minimize disruption. Maxoid supports unmodified apps with full security guarantees, and also introduces new APIs to improve usability. We show that Maxoid can improve security for popular Android apps with minimal performance overheads.