Explore a 23-minute conference talk from USENIX HealthTech '14 examining the use of Electrocardiograph (ECG) signals in cryptography for Implantable Medical Devices (IMDs) and Body Area Networks (BANs). Delve into the security implications of using interpulse intervals (IPIs) for authentication protocols, such as the H2H protocol. Analyze the challenges in extracting reliable randomness from ECG signals and discuss potential vulnerabilities in real-world settings. Investigate preliminary experiments on remotely observing ECG signals through video processing techniques, tracking subtle head movements and skin color changes. Gain insights into the security assumptions and potential pitfalls of ECG-based cryptographic protocols for medical devices.