Integrated circuit for embedding in smart cards, and method...

Registers – Records – Conductive

Reexamination Certificate

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Details

C235S382500

Reexamination Certificate

active

06299069

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an integrated circuit providing an authentication function in a smart card.
Conventional smart cards, also known as integrated-circuit cards, comprise an embedded integrated circuit such as a microcontroller having a central processing unit (CPU), a rewritable non-volatile data memory for storing data, and a masked read-only memory (ROM) for storing programs. In many smart cards, an authentication function is implemented by means of key data stored in the non-volatile data memory and an algorithm stored as a program in the masked ROM. Running on the CPU, the program uses the key data and other data, such as random-number data, to generate authentication data, which are then used to authenticate the identity of the card, or the identity of a host device with which the card communicates. A high degree of security can be provided by the use of long keys and complex algorithms. An integrated circuit comprising a CPU, however, has the disadvantages of being comparatively large and expensive.
If the CPU is not needed for other processing, an integrated circuit employing hard-wired logic for authentication can overcome these disadvantages, but the algorithms that can readily be implemented in hard-wired logic are limited in complexity, and do not provide a high level of security. Since a person who succeeds in penetrating a single card can sometimes compromise the security of an entire system, a system using cards with hard-wired authentication logic is at considerable risk.
Another problem with integrated circuits of both of the above types is that the authentication algorithm is unalterable, or at least, the algorithm cannot be altered easily. Alterations can be made only by modifying the photolithography masks used in manufacturing the integrated circuit, which is an expensive and time-consuming undertaking.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a small, inexpensive integrated circuit having a highly secure authentication function, for use in smart cards.
Another object of the invention is to provide a method of using the invented integrated circuit that enhances the security of the smart cards.
The invented integrated circuit has an interface circuit for external input and output of commands and. data, an electrically rewritable non-volatile memory storing at least one instruction file having a list of instructions, and an authentication data generator having logic circuits for executing the instructions, thereby converting random data into authentication data. The integrated circuit may also have a random data generator for generating the random data. The rewritable non-volatile memory preferably stores key data as well as the instruction file.
In a preferred configuration, the authentication data generator has registers for storing the key data and random data, a data processing unit using the key data to perform operations on the random data, an instruction register, and a control logic circuit. The data processing unit has a shift register into which the random data can be transferred, a bit replacement circuit, a bit-inverting circuit, a selector for selecting key data or random data, and an exclusive-OR logic circuit operating on the selected data and the contents of the shift register. The control logic circuit reads instructions one by one from the instruction file into the instruction register, and executes the instructions by controlling the data processing unit, thereby generating the authentication data.
The data processing unit may also have a register for saving and restoring the shift-register contents. The control logic circuit may also have logic for conditionally skipping instructions in the instruction file, for unconditionally skipping instructions, and for executing no-operation instructions.
When the rewritable non-volatile memory stores two or more instruction files, these files can be selected according to external information received by the interface circuit. For example, one instruction file can be used in converting random data generated in the integrated circuit to authentication data, to authenticate a host device, and another instruction file can be used to convert random data received by the interface circuit, for authentication of the smart card in which the integrated circuit is embedded.
A preferred method of issuing smart cards in which the invented integrated circuit is embedded is to write different instruction files in different cards. No-operation instructions are preferably inserted into the instruction files, as necessary, to make all instruction files have the same length.


REFERENCES:
patent: 5120939 (1992-06-01), Claus et al.
patent: 5225664 (1993-07-01), Iijima
patent: 5497418 (1996-03-01), Kudelski
patent: 5533123 (1996-07-01), Force et al.
patent: 5542081 (1996-07-01), Geronimi
patent: 5825882 (1998-10-01), Kowalski et al.
patent: 5914471 (1999-06-01), Van De Pavert
patent: 0481936 A1 (1991-02-01), None
patent: 0596276 A2 (1993-10-01), None
patent: 2698195 (1992-11-01), None
patent: 3-224083 (1991-10-01), None

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