Information is a valuable asset nowadays and there is a strong interest in ensuring the security of information transmitted within information systems. This paper focuses on the electromagnetic information leakage from PS/2 keyboards, in order to prove the possibility of capturing and disseminating signals containing useful information by employing common laboratory equipment. Although the PS/2 protocol is not new, it is still very common in many computer systems that are still in use, such as SCADA (Supervisory Control and Data Acquisition) systems in the industrial domain. The experimental results were obtained with equipment accessible to the general public - thus proving that access to such sensitive information can be attained with minimal and low cost resources, but also with TEMPEST equipment. There is presented a novel method of capturing and reconstructing the signal transmitted by a keyboard using PS/2 communication, with classical signal processing techniques.

Keywords: Correlation, Electromagnetic interference, Information security, Information systems, Keyboards