Published Paper Details:

Two-factor authentication (2FA) has become essential for digital security as mobile devices and Internet-of-Things (IoT) environments shape our daily interactions. It helps reduce risks linked to password issues like phishing and credential theft. This review paper examines how acoustic based authentication has evolved, focusing on active sound sensing methods that provide secure, zero-interaction 2FA. We start with early ambient audio techniques for shared key generation. The discussion then moves to sensor fusion methods, proximity detection in voice-enabled IoT settings, and finishes with advanced echo-based systems like Proximity-Echo. We explain the reasons behind each development phase and compare the technical trade-offs, especially regard ing usability, attack resistance, and efficiency. We also discuss the implications for embedded mobile systems. The paper ends with a practical workflow that combines active beep emission and echo signature analysis. We also suggest future research areas, including multi-modal sensor integration, post-quantum adaptations, and energy-efficient designs.