DE3051266C2 - Protector for access to data processor permanent memory - Google Patents

Abstract

The microprocessor with read and write functions in a programmable memory has the access to the memory protected to prevent fraudulent use. This is performed by use of a coded key in access and error memories. A microprocessor (1) is connected to a programmable memory (2) and to error and access memories (3,4). The error and access memories are of any required capacity and are electrically alterable only by the microprocessor. These memories are connected via the same data bus as the programmable memory. A program is a control memory enables the microprocessor to erase the access and error memories and to verify that a coded key entered into it is correct or not. This causes a bit to be entered into one of the memories. A verifuation process then occurs to allow or lock out successive operations.

Description

The invention relates to a method according to the preamble of Claim 1.

A method of this type is known from FR-OS 24 01 459. It is intended to protect against unauthorized access and is based on the Use of a device that the reading and writing operations a Microprocessor is assigned.

For certain applications, it is essential to have access to the read-only memory (PROM) on the information carrier by a Protect access keys associated with certain powers, read out or enroll in certain zones. In technology there is already numerous proposals for devices, the unauthorized thereof hold the access key through successive attempts to find out about a store. The best known of these devices is one that permanently stores faulty keys and operation locks once the number of errors a predetermined value exceeds. However, this device is ineffective when used alone  is used. Observing the changes in the write current in the This is because memory enables the passage of a correct key to determine with precision, on the condition that this current is correct is limited so that the errors cannot be recorded. This difficulty is due to the above-mentioned FR-OS 24 01 459 fixed that a symmetrical function of the writes by this Microprocessor is provided. In particular, is always in memory registered, regardless of whether the access key is correct or incorrect, and the unauthorized person cannot provide any information about the results of the actions taken by him.

When registered, this device is perfect because of the memory needs to be changed anyway. The symmetry is by using a Error bits or a bit assigned to the word to be written guaranteed.

If access to readout is protected with a key So, it is necessary to first put in one for these purposes write the intended field of the memory.

This way, all accesses are stored in an access memory saved, which is advantageous if the number of protected Read operations should be limited.

As far as the read-only memory itself is concerned, this is how it works however, inconvenient because it requires a relatively large amount of storage space.

Furthermore, this method of operation is also not applicable when access to read for an unlimited time, as long as the memory is not full, should be protected.

The object of the invention is the development of a method of mentioned type in that a principally unlimited number of Uses of the information carrier with a small size for storage the memory area provided for access and error codes becomes.

This object is achieved by the features of patent claim 1.  

Advantageous developments of the invention are in the sub claims specified.

From the publication "IBM Technical Disclosure Bulletin", Vol. 20, No. 10, March 1978, pages 4055 and 4056 it is already known per se, one electrically rewritable memory (EAROM) on a portable informa holder for storing value units and authorization keys use. This information carrier in the form of a credit or identification As such, the activity card is inserted into an electronic control unit and is just a memory card.

An embodiment of the invention will now be described with reference to FIG Drawing described in more detail. The drawing shows:

Fig. 1 is a block diagram of the information carrier; and

Figure 2 is a flow diagram of the operations that must be performed to write a bit symmetrically.

In addition to the microprocessor 1 and the programmable read-only memory 2 , the information carrier shown in FIG. 1 contains a memory with a fault memory area 3 and an access memory area 4 . The error and access memory areas can be of any size; however, they must be electrically erasable by the exclusive action of the microprocessor.

This exclusivity means that these storage areas are not may be erasable from devices located outside of the recording carrier. This can be done by locking means that are obtained by programming and are not described further here Need to become.

It should be noted that the memory areas 3 , 4 are connected directly to the data and address bus, which connects the microprocessor 1 to the memory PROM 2 . The memory areas 3 and 4 can be designed as so-called EAROM memories (electrically changeable read-only memories). For these memories, reference is made to the work "Les microprocesseurs" by Rodnay Zaks and Pierre le Beux, ed. Sybex, 313, rue Lecourbe, 75015 Paris, pp. 77-81.

The operation of the device can take various forms, each of which is carried out by means of a program which is written into a control memory. In the embodiment shown in FIG. 2, the access memory area 4 is initially cleared (step 100 ). In step 101, the microprocessor checks whether the requested access is carried out with the correct key. If the key is correct, an information bit is written into the access memory (step 102 ); however, if the key is not correct, this information bit is written into the error storage area 3 (step 104 ). Steps 103 and 105 consist of checking whether a bit has actually been written into one or the other memory area. There is an error if there was no write operation.

This way of working is due to the symmetry of the operations performed marked, whether the key is right or wrong. The previous deletion of the access memory enables this area reuse every reading process without restriction.

Claims (3)

1. A method for recording access information or error information in a portable information carrier for the storage and processing of information, with a microprocessor and, if necessary, an associated, only programmable fixed value memory, the microprocessor writing and reading elements for writing and reading in parts of the read-only memory and receiving means for external information to be written into the programmable read-only memory and recognition of an external authorization key, and an error code is stored in each case if the key entered is incorrect, and an access code is stored if the key is recognized as correct, characterized in that for storing the error code and the access code, a separate, electrically rewritable memory ( 3 , 4 ) is used, which is divided into an access memory area and an error memory area, is that before the Erke If the authorization key is correct or incorrect, the access memory area is deleted, that a bit is written into the access memory area each time an attempt is made to access with an appropriate authorization key, that a bit is written into the error memory area for an incorrect authorization key, that a check is made as to whether that A bit has been written correctly and that the writing of a bit and the deletion of the access memory area take place exclusively under the influence of the microprocessor ( 1 ). 2. The method according to claim 1, characterized in that a Error counter the number of incorrect entries of the authorization key counts. 3. The method according to any one of the preceding claims, characterized characterized in that an error signal is output when a Write process was not carried out correctly.