Abstract: A computer communications control system is provided for authenticating the authorization of a user of computer equipment such as a terminal of a computer network, more specifically communicating data terminal equipment that is connected through a communications link to other computer equipment such as a host computer. The system utilizes a security unit that is associated with and connected to the user's terminal. The security unit operates in conjunction with the other computer equipment to which the user's terminal is linked, for example a host computer, to check the authorization of the user to access the host computer by requiring that an encryption device which has been assigned to the user be received in a port that is defined by the security unit in order that the security unit can respond properly to query signals which are sent along the communications link from the host computer.

Abstract: A security control system is provided for interactively identifying and authenticating the authorization of a user of a communications terminal, and optionally providing a means for decoding and encrypting communications signals transmitted to and from the terminal. The system utiizes a security unit that is associated with the terminal, and requires that an encryption device which has been assigned to the user be received in a port that is defined by the security unit in order that the security unit can respond properly to query signals which are sent along a communications link that couples the terminal to other communications equipment. Communications units at both ends of the communications link operate in synchronization such that each new authentication query signal that is sent from one of the units will be answered by an appropriate, newly calculated authenticating signal from the other, whereupon the unit that has sent the query signal checks the received response for correctness of calculation.