JPS6117175A - Integrated circuit with confidential protection circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a security circuit that makes it impossible to determine the functions of a semiconductor integrated circuit by analysis by anyone other than the manufacturer.

(Prior art) Semiconductor integrated circuits that are made on a half-time basis or specially ordered are, by their nature, used by those who purchase them from the manufacturer, so it is desirable for the manufacturer that their functions are not known to others. .

However, with the current semiconductor integrated circuits, after a certain amount of time, it is possible to determine the function of the semiconductor integrated circuit by applying a signal from its input terminal using an appropriate method and examining the signal appearing at its output terminal. Figure 1 shows a functional block diagram of a conventional semiconductor integrated circuit.

An input signal applied to the input circuit 1 is processed by the internal circuit 2 and outputted from the output circuit 3 as an output signal. Therefore, there must be a certain correlation between the input signal and the output signal.
By adding various input signals or special input signals, the functions and operations of the internal circuit 20 can be known from the output signals. It is not desirable for the manufacturer to know the functions and operations of the internal circuit 2, since this means that the semiconductor integrated circuit can be easily simulated.

(Problems to be Solved by the Invention) An object of the present invention is to obtain a semiconductor integrated circuit in which the functions, operations, and configurations of its internal circuits cannot be known to anyone other than the manufacturer.

(Means for Solving the Problem) According to the present invention, a confidential signal input terminal, a confidential signal input terminal for determining whether or not a signal input manually to the confidential signal input terminal is a predetermined confidential signal; A semiconductor integrated circuit having an internal circuit whose operation is controlled by the output of the determination circuit is obtained.

(Function) The present invention utilizes a part of the semiconductor integrated circuit to not accept input signals or output signals unless a preset confidential signal is input, or to change internal functions. Secrecy can be protected by controlling internal circuits such as

(Example) Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 2 shows a functional diagram according to an embodiment of the present invention.

Input circuit 11. The internal circuits 12 and 12' and the output circuit 13 are the input circuits 1. and 12' shown in FIG. Internal circuit 2. Each corresponds to the output circuit 3. When a signal is input to the confidential signal input circuit 14, the signal is input to the comparison circuit 15, and compared with the confidential signal already set in the confidential signal setting circuit 16. Only when they match, a matching signal appears and input is permitted. The circuit 17 and the output permission circuit 18 are set to a signal passing state, the input signal is transmitted to the internal circuit 12, and the output of the internal circuit 12' is transmitted to the output circuit 1.
3.

Furthermore, an internal signal enabling circuit 19 is provided between the internal circuits 12 and 12', and by stopping signal transmission or changing the logic between the internal circuits 12 and 12', it becomes even more difficult to investigate from the outside. It can be done.

(Effects of the Invention) According to the present invention, since no one else can operate the integrated circuit normally unless they know the confidential signal, the secrecy of the functions, operations, and configurations of the internal circuits can be reliably maintained.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of a conventional semiconductor integrated circuit. FIG. 2 is a functional block diagram of a semiconductor integrated circuit according to an embodiment of the present invention. 1.11...Input circuit, 2,12.12'...
...Internal circuit, 13...Output circuit, 14.
... Confidential signal input circuit, 15 ... Comparison circuit, 16 ... Mark/Secret signal setting circuit, 17 ......
Input permission circuit, 18...Output permission circuit, 19.
...Internal signal enable circuit. Raku/Figure

Claims (1)

[Claims] The device includes a confidential signal input terminal, a determination circuit that determines whether a signal input to the confidential signal input terminal matches the confidential signal, and a signal processing circuit whose operation is controlled by the output of the determination circuit. An integrated circuit with a featured security circuit.