JPH01310385A - Data processor with deciphering mechanism - Google Patents

Abstract

PURPOSE:To disable deciphering even when data is duplicated by selecting key data with specification information included in enciphered data, and limiting the number of times of writing to a storage means and stopping a deciphering function. CONSTITUTION:A register selecting circuit 4 selects a register A and data from an external storage device and the key data are ORed exclusively (EXOR) to perform deciphering. Further, registers B1-Bn and a counter circuit 2 which counts the number of times of writing to those registers are provided to limit the number of times of the rewriting of register contents. Then when data to be protected is enciphered, register selection instructions for specifying the key word are inserted at plural positions and corresponding key words are read out of the registers B1-Bn and EXORed. Then when the limited number of times of the counter circuit 2 is exceeded, the deciphering processing function is stopped to disable the deciphering even when the data is duplicated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a data processing device having a decryption mechanism.

(Prior Art) Numerical data and program data processed by a data processing device using a normal CPU, for example, in the case of a numerical control device, are read from an NC tape and then stored in a non-volatile memory. . Or ROM from the beginning
Some data is stored in fixed storage means such as, and read out as needed.

If these various types of data are independently developed by manufacturers or users, the cost for doing so would be large, so measures are often taken to prevent them from being easily copied. Normally, when reading data,
The data reading mechanism will not work unless a certain password code is entered manually, or the RAM in the CPU will be disabled.
.

When a ROM or the like is included, a device has been devised so that data can be read only when data is set in a specific bit.

(Problem to be solved by the invention) Also, for the same purpose as the conventional copy prevention device,
For example, a password processing device disclosed in Japanese Unexamined Patent Publication No. 62-269215 has also been developed. This password processing device is configured so that when the same password as the set password is entered to start a special mode and a predetermined work is performed, the set password itself is changed after the work in the special mode is completed. Even if the user knows the password, the user cannot activate the specific mode again using only that password.

However, even in this case, there is a certain limit to the number of passwords that can be set, and there is also the problem that once the contents are copied, the existence of the password processing device becomes meaningless.

The present invention was made to solve the above problems, and
The program data and numerical data themselves are encrypted, and the CPU
It is an object of the present invention to provide a data processing device having a decryption mechanism that decrypts the decryption data on the side, thereby rendering meaningless copying of data stored and used in an external storage device.

(Means for Solving the Problems) According to the present invention, in a data processing device that has a decryption mechanism that decrypts encrypted data by internal calculation and performs data processing, a plurality of key data for decryption is used. a plurality of storage means for storing the key data, a prohibition means for prohibiting reading of the key data from the storage means, a decryption processing means for selecting and decrypting the key data based on specified information included in the encrypted data, and the storage means. and a limiting means for limiting the number of times key data in the means is rewritten, and the processing function of the decryption processing means is stopped when the number of times the storage means is rewritten exceeds the set number of times. A data processing device having a decoding mechanism can be provided.

(Operation) The data processing device having the decryption mechanism of the present invention can store key data necessary for decrypting encrypted data.
It is designed to process data while decoding the code by selecting it based on specified information included in the encrypted data, and even if the encrypted data is duplicated, it can be decoded. It can be virtually impossible to discover the key data for the purpose, both temporally and physically.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The drawing is a block diagram showing an example of a CPU constituting a data processing device. Inside the CPU, in addition to normal arithmetic processing functions, a decryption mechanism described below is provided.

The registers A, B1 to Bn, which are a plurality of storage means in which a plurality of key data for decoding are stored, are constituted by nonvolatile storage means, such as an EPROM or an EEPROM.

The counter circuit 2 that counts the number of writes to these registers is provided with a count register, and a limit count number is stored therein.

3 is a read prohibition circuit that prohibits reading the contents of the register; this is register A;

A plurality of key data for decryption written in 81 to Bn are protected.

A register selection circuit 4 that selects these registers A, Bl to Bn selects register A for automatic change when the CPU 1 is started, and selects a predetermined register from a plurality of registers 81 to Bn according to a selection command input thereafter. is selected and its contents are output to the exclusive OR circuit 5, which is a decoding processing means for decoding the encrypted data.

On the other hand, the data at the beginning of the data to be protected is encrypted so that it can be decrypted by performing EXOR with the key data stored in register A. Write this key data to register A, and write predetermined key data to other registers as necessary.
After writing, enable the register read inhibit circuit. The data to be protected is obtained only when the exclusive OR circuit 5 performs an exclusive OR (hereinafter abbreviated as EXOR) with the key data stored in each register 81 to Bn. Apply a certain amount of encryption so that it can be restored.

The operating principle of the data processing device having the above configuration will be explained next.

When the power is turned on, the register selection circuit 4 selects the register A, and the data manually entered from the external storage device is decoded as EXOR data with the key data stored there.

If this is all there is to it, even if the corresponding key data is not stored in register A when encrypted data is copied, the contents of register A will be set to the corresponding key data. It becomes possible to use the copied encrypted data.

However, the feature of the above embodiment is not limited to this, and since a plurality of registers 81 to Bn and a counter circuit 2 that counts the number of writes to these registers are provided, protection of data contents is ensured. done to.

In other words, when encrypting data to be protected, register selection instructions for specifying keywords are inserted in multiple locations, and register B is selected depending on the data read.
This is because the encryption is decoded by calling the corresponding keywords from 1 to Bn and performing EXOR between them. Therefore, even if key data corresponding to the beginning of the data is found, the data cannot be decoded unless multiple keywords are also known. Since the limit count number is set, even if an attempt is made to decrypt the encrypted data by sequentially rewriting the contents of multiple registers 81 to Bn, the number of rewrites exceeds the set number of times. At this time, the decoding processing function stops, making it impossible for the CPU to continue the decoding work.

Note that when encrypting data, it is basically unnecessary to rewrite the key data input to the internal registers A, Bl to Bn of the CPU to process it, so the number of rewrites should be limited. It does not cause any inconvenience in itself.

In addition, if the limit count number of the counter circuit is exceeded, there is no means of recovery, that is, the CPU
Instead of permanently stopping the operation of CPU 1, all key data input to internal registers A, Bl to Bn of the CPU may be erased.

As above, this invention has been described in some detail with respect to its most preferred embodiment, but the description of the preferred embodiment does not include variations in detailed parts of the configuration and does not go against the spirit of the invention as described in the claims. It is clear that various modifications or combinations thereof may be made.

(Effects of the Invention) As explained above, according to the present invention, by encrypting program data and numerical data to be protected, it becomes virtually impossible to decode the data, and as a result, data copying becomes impossible. It is possible to provide a data processing device having a decryption mechanism that is effective in preventing such problems.

[Brief explanation of the drawing]

The drawing is a block diagram showing one embodiment of the present invention. 1...CPU, A, Bl~Bn...Register, 2.
...Counter circuit, 3...Read prohibition circuit, 4...
- Register selection circuit, 5... exclusive OR circuit. Patent applicant FANUC Corporation

Claims (1)

[Claims] A data processing device having a decryption mechanism that decrypts encrypted data by internal calculation and performs data processing includes a plurality of storage means for storing a plurality of key data for decryption, and a storage means for storing key data from the storage means. The storage device includes a prohibition means for prohibiting reading, a decryption processing means for selecting and decrypting the key data based on specified information included in the encrypted data, and a restriction means for limiting the number of times the key data in the storage means is rewritten. A data processing device having a decryption mechanism, characterized in that the processing function of the decryption processing means is stopped when the number of times the storage means is rewritten exceeds a set number of times.