Implementing and Optimizing an Encryption Filesystem on Android

The recent surge in popularity of smart handheld devices, including smart-phones and tablets, has given rise to new challenges in protection of Personal Identifiable Information (PII). Indeed, modern mobile devices store PII for applications that span from email to SMS and from social media to location-based services increasing the concerns of the end user's privacy. Therefore, there is a clear need and expectation for PII data to be protected in the case of loss, theft, or capture of the portable device. In this paper, we present a novel FUSE (File system in User space) encryption file system to protect the removable and persistent storage on heterogeneous smart gadget devices running the Android platform. The proposed file system leverages NIST certified cryptographic algorithms to encrypt the data-at-rest. We present an analysis of the security and performance trade-offs in a wide-range of usage and load scenarios. Using existing known micro benchmarks in devices using encryption without any optimization, we show that encrypted operations can incur negligible overhead for read operations and up to twenty (20) times overhead for write operations for I/O-intensive programs. In addition, we quantified the database transaction performance and we observed a 50% operation time slowdown on average when using encryption. We further explore generic and device specific optimizations and gain 10% to 60% performance for different operations reducing the initial cost of encryption. Finally, we show that our approach is easy to install and configure across all Android platforms including mobile phones, tablets, and small notebooks without any user perceivable delay for most of the regular Android applications.