Abstract: An electronic security card and system for authenticating ownership of the card is disclosed. The system comprises a security card and a terminal. The security card includes logic circuitry which is responsive to a plurality of input signals and which is operative to provide an output signal if the input signals are in a preselected sequence and to develop a feedback control signal which is applied to, and deactivates, the logic circuitry if the input signals are not in the preselected sequence. The terminal comprises a source of input signals, a switching network for selectively interconnecting the source to the logic circuitry so as to apply a sequence of input signals to the logic circuitry when the security card is received by the terminal, and an indicator responsive to the output signal and operative to provide an indication of the authenticity of the user of the security card.