Abstract: Filter networks are incorporated within a software protection hardware device which is plugged into a communications port of a computer which device will select bits or combinations of bits emanating from the communications port resulting from commands of a controlling software in use with the computer which is desired to be protected. The filter networks select the bits of a disguised predetermined control code which when matched with a stored reference code results in an output from the filter used to activate functions within the protection device. A stream of bits including a disguised predetermined control code issuing from the computer through the security device are compared with a stored reference code in a programmable memory. When a match occurs an output emanates providing an acknowledgment code to the computer indicating that the hardware device has been plugged in and is a proper one.

Abstract: A method and apparatus are provided for protecting computer software using an active coded hardware apparatus which is adapted to be connected by an interface connector to a communications port of a computer. The computer is directed by a coded software program in which a small section of the code of the computer software interrogates the communications port periodically to determine if the active coded hardware device is present and connected. The active coded hardware device has a permanently established preset code on an active presettable counter circuit which code is transmitted when interrogated. If the active coded hardware device is present when interrogated and the correct code returned through the communications port of the computer, the program is permitted to continue insuring that the software is properly protected at all times. The active coded hardware device with its particular code and circuitry are sealed in epoxy as a deterrent against tampering.