Context-based authentication is a method for transparently validating another device's legitimacy to join a network based on location. Devices can pair with one another by continuously harvesting environmental noise to generate a random key with no user involvement. However, there are gaps in our understanding of the theoretical limitations of environmental noise harvesting, making it difficult for researchers to build efficient algorithms for sampling environmental noise and distilling keys from that noise. This work explores the information-theoretic capacity of context-based authentication mechanisms to generate random bit strings from environmental noise sources with known properties. Using only mild assumptions about the source process's characteristics, we demonstrate that commonly-used bit extraction algorithms extract only about 10% of the available randomness from a source noise process. We present an efficient algorithm to improve the quality of keys generated by context-based methods and evaluate it on real key extraction hardware. MOONSHINE is a randomness distiller which is more efficient at extracting bits from an environmental entropy source than existing methods. Our techniques nearly double the quality of keys as measured by the NIST test suite, producing keys that can be used in real-world authentication scenarios.

The emergence of advanced in-vehicle infotainment (IVI) systems, such as Apple CarPlay and Android Auto, calls for fast and intuitive device pairing mechanisms to discover newly introduced devices and make or break a secure, high-bandwidth wireless connection. Current pairing schemes are tedious and lengthy as they typically require users to go through pairing and verification procedures by manually entering a predetermined or randomly generated pin on both devices. This inconvenience usually results in prolonged usage of old pins, significantly degrading the security of network connections.

The emergence of the Internet of Things (IoT) and pervasive computing challenges in securely and conveniently connecting devices with limited user interfaces. In particular, discovering and bootstrapping a wireless connection (e.g., Wi-Fi and Bluetooth Low Energy) between two devices that share no prior knowledge, commonly known as pairing, often requires users to go through cumbersome tasks of manually discovering the target device and entering a long passkey. When the devices do not have a proper user interface to enter a passkey, the security of pairing is often given up, leaving the communication vulnerable to a number of attacks. To alleviate this challenge, we propose a usable and secure out-of-band (OOB) communication method called SyncVibe, leveraging the inherent nature of close-proximity transmission of mechanical vibration. SyncVibe utilizes a vibration motor and an accelerometer, that are already ubiquitously available or easy to embed in mobile and wearable devices, to transmit and receive pairing information. By simply keeping two devices in direct contact, the user can bootstrap a secure, high-bandwidth wireless connection without manual pairing procedures. The proposed method maximizes accuracy and effective data throughput with a vibration clock recovery technique, which inserts a minimal amount of extra bit patterns to assure synchronization between the transmitter and the receiver. In addition, SyncVibe can automatically adjust its detection thresholds in response to various vibration noises and transmission media. Our implementation of SyncVibe demonstrates high-accuracy transmission, proving itself as a suitable OOB communication channel for short data transmission for secure device pairing.