Mobile-device theft and loss have reached gigantic proportions. Despite these threats, today’s mobile devices are saturated with sensitive information due to operating systems that never securely erase data and applications that hoard it on the vulnerable device for performance or convenience. This paper presents CleanOS, a new Android-based operating system that manages sensitive data rigorously and maintains a clean environment at all times. To do so, CleanOS leverages a key property of today’s mobile applications — the use of trusted, cloud-based services. Specifically, CleanOS identifies and tracks sensitive data in RAM and on stable storage, encrypts it with a key, and evicts that key to the cloud when the data is not in active use on the device. We call this process idle eviction of sensitive data. To implement CleanOS, we used the TaintDroid mobile taint-tracking system to identify sensitive data locations and instrumented Android’s Dalvik interpreter to securely evict that data after a specified period of non-use. Our experimental results show that CleanOS limits sensitive-data exposure drastically while incurring acceptable overheads on mobile networks.
This paper presents Keypad, an auditing file system for theftprone devices, such as laptops and USB sticks. Keypad provides two important properties. First, Keypad supports finegrained file auditing: a user can obtain explicit evidence that no files have been accessed after a device’s loss. Second, a user can disable future file access after a device’s loss, even in the absence of device network connectivity. Keypad achieves these properties by weaving together encryption and remote key storage. By encrypting files locally but storing encryption keys remotely, Keypad requires the involvement of an audit server with every protected file access. By alerting the audit server to refuse to return a particular file’s key, the user can prevent new accesses after theft.
We describe the Keypad architecture, a prototype implementation on Linux, and our evaluation of Keypad’s performance and auditing fidelity. Our results show that Keypad overcomes the challenges posed by slow networks or disconnection, providing clients with usable forensics and control for their (increasingly) missing mobile devices.