Registers – Systems controlled by data bearing records – Credit or identification card systems
Reexamination Certificate
1999-06-23
2002-07-23
Lee, Michael G. (Department: 2876)
Registers
Systems controlled by data bearing records
Credit or identification card systems
C235S379000, C235S441000, C235S492000
Reexamination Certificate
active
06422461
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention concerns a method and a system to ensure that modules to be connected to an apparatus comprising a processor are of a specific type, wherein modules of the specific type are provided with a code circuit capable of outputting one or more code words on request, and wherein the processor of the apparatus, when a module has been connected to the system, reads one or more of said code words from the code circuit of the apparatus, compares the read code word or words with reference code words stored in the apparatus, and rejects the module if the read code word or words do not correspond to the reference code words.
The invention also concerns a module capable of being connected to such an apparatus, and a code circuit as well as a storage medium for storage of data and for use in such a system.
BACKGROUND OF THE INVENTION
Many technical systems comprise an apparatus to which a plurality of modules may be connected. Typically, it may e.g. be an electronic device comprising a central control unit to which a plurality of external printed circuit cards may be connected depending on the use. The electronic device may e.g. be a network element in a telecommunications network or a control system for a manufacturing process.
Other examples of such modules may be battery packet for a mobile telephone, a component or a spare part which may be connected to the electrical system in a car or to the car in general, or a probe for a measuring instrument.
Such systems have the advantage that the technical solution may be composed of individually selected modules.
For several reasons, when a module is connected to the system, it may be expedient to be able to detect whether the other module is of a specific type. It may e.g. be a matter of checking that the connected module is supplied by the supplier who has also supplied the main system, since this is the only way to ensure that the system operates as specified by the supplier. This may e.g. be the case where probes for measuring instruments are calibrated for each individual measuring instrument, and where it may thus be essential to ensure that the correct probe is connected.
In respect of high-technology products, extension modules and spare parts for the products are produced in large numbers. However, it happens frequently that other suppliers make copies having the same function as the original products, but at a lower price. It may be expedient for a manufacturer of the original products to protect himself against copy products, partly because reliability and quality might be impaired when the original modules are replaced by copy modules, and partly because of the loss of earnings from the sale of the original products.
It is known to prevent interconnection of such elements by various physical obstacles, which, however, are generally easy to imitate by a copy manufacturer.
Further, the art in the software field includes a large number of methods for access control and limitation of copying of e.g. discs or CD-ROM with programs such as e.g. games. These methods, however, are not suitable for preventing connection of hardware modules to e.g. an electronic apparatus.
Known are also electronic systems in which a code circuit on a module must apply a code word before the module will be accepted by the main system, as is known also from e.g. payment cards in financial systems.
When mechanical and electronic systems can be physically accessed, however, it will frequently be possible to expose details of the structure and thereby evade the methods which just permit combination with certain modules. In the case of the code word which has to be applied by the module, it will e.g. be possible to find the code word by outputting it in the same manner as is done in the original system. Thus, all that needs to be done is to obtain a sample of the original module, and then the code word of this module may be read and copy modules may be manufactured with the same code word.
From U.S. Pat. No. 4,851,653 a system in which a confidential code is introduced to a memory card to get access to the memory of the card is known. On the card the introduced code is compared to a reference code and only in case of a match between the introduced code and the reference code access is provided to the memory. A built-in time delay ensures that a certain time must pass between each attempt at introducing a code. In this manner it is ensured that an unauthorized user cannot just try with a high number of different codes in a short time. By systems of the above described type, in which modules are connected to an apparatus, this system does not, however, provide any security, because an unauthorized card can just read the code word used by an authorized card and subsequently use the same code word, since only one reference code is used. Therefore, the system can be cracked by a simple interception.
A similar system is used according to EP 379 333 in which a finger print of a person is compared with a reference finger print stored in digital form on a credit card. Also here, a single reference code that can be uncovered by interception is used, and therefore also this system does not provide sufficient security in the systems mentioned above.
WO 86/03864 discloses a system for establishing connection between a computer terminal and a main computer. In stead of a usual code word or pass word this system uses a new random code word each time a connection between a given terminal and the main computer is to be established. Before termination of a connection the terminal generates a new code word, which is sent to the main computer in which it is stored. It is also stored in the terminal itself. Next time this terminal wishes a connection to the main computer it must be able to provide exactly this code word to the main computer. In this way it is ensured that an unauthorized terminal cannot just intercept the code word from an authorized terminal and subsequently use the same code word itself. However, this system only ensures that the main computer—when the system has been initialized and is in normal use—only accepts communication with a terminal to which it has communicated before. When a terminal is connected to the computer for the the first time the security procedure must be by-passed and, therefore, the security is totally dependent of the person taking care of the connection of new terminals to the system. Therefore, this principle cannot be used in the situations mentioned above and with which the present invention is concerned.
Another principle that attempts to overcome the risk of interception of a code word is known from DE 44 11 780. Here, the code word is changed dependent on the actual time. A user introduces on a terminal or a module a primary code word which is then converted into a corresponding secondary code word. This code word is combined with a time signal representing the actual time, which is received from a radio transmitter, and the result is used as address to a ROM device of e.g. 32 kbytes. The content of the selected address is transmitted to the receiver unit which has a similar ROM device and knows the correct secondary code word. Also here the known secondary code word is combined with the actual time signal to form an address to the ROM device and the resulting content must correspond to that received from the terminal. As the actual time signal is changed all the time a code word that is intercepted can only be used for a very short time, i.e. until the time signal is changed. This could e.g. happen every 6 minutes. However, this principle has the drawback that if an unauthorized user once knows the principle he only has to get access to an authorized unit and then copy the ROM device, which can be done in a very short time. With a copy of the original ROM device the unauthorized module can without any difficulty generate correct code words. It is also a drawback with this principle that the central apparatus as well as each unit or module must be provided with a radio receiver for the time s
Baker & Botts L.L.P.
DSC Communications A/S
Le U Chau
Lee Michael G.
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