Side channel attack on digital door lock with vibration signal analysis: Longer password does not guarantee higher security level

Digital door lock system is a widely used physical security system. It restricts unauthorized accesses and protects assets or private spaces. However, once its password has been exposed to unauthorized people, it becomes useless. In this paper, we propose a novel side channel attack model, which enables a cracking of a digital door lock password. We noted that when people press the key-lock button, irrespective of how careful they are, the generated vibrations differ with the location of the button pressed. Our model uses and analyzes the natural phenomenon of vibration to infer passwords. Under our attack, the ease of password inference depends on the number of distinguishable buttons rather than password length. The results of our experiments contradict the commonly held security principle that a longer password guarantees a higher level of security.