The microphone array sensor attack on keyboard acoustic emanations: Side-channel attack

Common people have no awareness of silent attack which exploits information leakage from acoustic of electronic devices. In computer mechanism, physical information is entered through the input device such as a keypad or a keyboard. Computer user types password or pin code by pressing the key button which emits an acoustic sound. The sound is analyzed by an attacker with computational methods to recognize the keys. Various attack of keyboard acoustic emanations was developed to find vulnerabilities as a risk assessment of keyboard. Authors developed the microphone array sensor attack to gain high accuracy in key recognition with a simple method. Sensors are two microphones which are placed sequential and linear in front of the target to acquire time difference. Arrival time is analyzed to define a starting time value for TDoA estimation and to calculate the direction of the sound source. The attackers can discover the location of the key by the geometric approach and without training data for key classification. The results are 86 percent accuracy of 300 keystrokes and 100 percent of 13 keys recognized. It indicates the significant risk of attack and should realize as a serious threat of keyboard vulnerabilities.