Summary
Smartphones and wearable devices such as smartwatches have become part of everyday life, offering people convenient access to personal, health, and digital services. Some emerging systems use heart-based biometric signals, captured through photoplethysmography (PPG) sensors in these devices, to authenticate users continuously without requiring passwords or active interaction. This seamless, unobtrusive form of authentication can enhance both security and user experience. However, PPG-based continuous authentication also introduces new privacy and cybersecurity risks if attackers can fool the s
