JPS63182758A - Information memory - Google Patents

Abstract

PURPOSE:To secure the high safety by combining the external input keys with the internal keys proper to each device for ciphering. CONSTITUTION:An external key holding part 1 stores the external input keys and an internal key memory part 2 stores the internal keys proper to each device. The data supplied from outside are ciphered via the external and internal keys and stored in a memory means 6. Thus it is possible to make it extremely hard to read correctly the recorded contents with only the keys set from outside. While the recorded contents can be easily copied to another medium and only the device used for writing can read out correctly the decoded information. As a result, it is impossible to use the recorded programs, etc., although they can be copied.

Description

[Detailed description of the invention] (Industrial application field) The present invention is an information storage device using an encryption method.

(Prior Art) The following methods are known as methods for protecting the confidentiality of data on a storage medium and for preventing the copying and use of stored programs and the like. Regarding data confidentiality, a method is known in which original data is encrypted and then stored on a medium, and this is a method in which encryption and decryption are performed using an encryption key. On the other hand, there are known methods to prevent programs from being copied and used on multiple devices, such as applying a special format to the medium or changing the sector length. This method adopts the following method.

(Problems to be Solved by the Invention) First, data secrecy laws based on encryption have the risk that ciphertext can be decoded into plaintext if only the value of a key such as a password is known. The first object of the present invention is to improve the safety against such key theft.

Furthermore, if a program or the like is recorded in a special format on a storage medium to prevent copying, the format of the recording may be revealed by analyzing the program or the like for reading it. In addition, in this case, it also prevents the creation of a backup medium, which has the disadvantage that recovery is impossible if the contents of the medium are destroyed. A second object of the present invention is to not prevent the copying of programs, etc. on a medium, and to prevent the copied medium from being used on a plurality of devices at the same time.

(Means for solving the problem) A means for storing keys inputted from the outside, a means for storing an internal key unique to the device, a storage means for storing information, and a means for storing the data inputted from the outside. Encrypting using a key and an internal key and storing it in the storage means,
An information storage device comprising: a cryptographic processing section that decrypts information read from the storage means using the external and internal keys.

(Operation) In order to correctly read information recorded on a storage medium using this device, both a key unique to the device used to write the information and a key set externally at that time are required. This makes it extremely difficult to read the recorded contents correctly using only keys set from the outside.

Also, since recording on a medium can be done in a normal format, it is easy to copy the recorded content to another medium, but for the reasons mentioned above, it is only possible to copy the recorded content to another medium. Since it is possible to read correctly decoded information, even if programs etc. recorded on this device are copied, it is impossible to use them on multiple devices at the same time.

(Example) Next, an example of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows an overview of one embodiment, in which keys set from the outside are recorded in an external key holding section 1. Further, a device-specific key is held in the internal key storage section 2. By combining these keys, the encryption processing unit 3 encrypts the input data 4 and decrypts the encrypted data 6 on the storage device. There are two ways to combine external keys and internal keys: generate a new key using four arithmetic operations, logical operations for each bit, etc., and use that key for actual encryption/decryption, or use one key for encryption. For example, after decrypting the data, the data is encrypted again using the other key.

Here, we have adopted an encryption method that allows the correct original information to be obtained only by using the exact same combination of internal and external keys as those used when writing, and at the same time, as will be described later. By devising ways to prevent the internal key held within the device from being read directly from the outside using methods such as this, it is virtually impossible to read the recorded contents correctly without the device used for writing. Can be done.

The example shown in FIG. 2 is an example in which the device shown in FIG. 1 is applied to information security. By making the internal key storage section 8 removable from the main body of the cryptographic processing apparatus, it is possible to independently manage the internal keys used during writing. Therefore, even if the value of the foreign key were to be known, it would be almost impossible to read the recorded contents without using the internal key, so it is better to record the information more securely. is possible. Also, as shown in Fig. 3, the storage medium 9
When using an easy-to-carry medium such as a floppy disk, the contents can only be read when the internal key storage unit 8 used for writing and the recording medium 9 are together, so the medium must be transported, etc. It is possible to make the safety even higher.

Figure 4 shows an example of use to prevent copying and use of programs, etc.
Internal key storage device 8 used for writing as well as the upper case
Correct reading of recorded contents is only possible with devices that have this. Therefore, since the storage medium 9 and the internal key storage section 8 can only be used as a unit, duplication of the internal key storage section 8 can be prevented by prohibiting reading of the internal key value using a method described later. I can do it. Therefore, even if a large number of media are copied, it is possible to prevent them from being read and used at the same time.

The following methods can be considered to actually prevent reading of internal key values. For example, if this device is integrated into one LSI
The internal key is written to the internal memory, and the LSI has a writing function for the internal key but not a reading function, so that the internal key value cannot be read from outside. Reading can be prevented. Alternatively, when storing the internal key using a general FROM, etc., it is possible to make it impossible to read it from the outside by completely insulating the terminals, wiring, etc. of the LSI.

(Effects of the Invention) Conventionally, encryption was performed only using a key value input from the outside, but in the present invention, the actual encryption is performed in combination with an internal key unique to each device. Even if it is possible to know the value of a foreign key, in order to actually read the encrypted text correctly, it is possible to require a huge amount of calculation that is virtually impossible to calculate. It has become possible to ensure higher safety.

In addition, by allowing the copying of data recorded on a medium but preventing the copying of the key held within the device, it has become possible to back up data and programs while preventing copying.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the basic configuration of this device, Figure 2 is a configuration diagram when applied to information confidentiality, Figure 3 is a configuration diagram when external storage media is targeted, and Figure 4 is a diagram showing the configuration when applied to information confidentiality. FIG. 2 is a configuration diagram when applied to prevent copying and use of a program on an external storage medium. In the figure, 1 is an external key holding unit, 2 is an internal key storage unit, 3 is a cryptographic processing unit, 4 is input data, 5 is output data,
6 is a storage medium, 7 is an external key, 8 is a removable internal key storage unit, and 9 is a removable storage medium.
G1. Agent: Susumu Uchiatsu, Patent Attorney
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Claims (1)

[Claims] means for storing a key input from the outside, means for storing an internal key unique to the device, storage means for storing information, and encrypting data input from the outside using the external key and the internal key. While storing in the storage means,
An information storage device comprising: a cryptographic processing section that decrypts information read from the storage means using the external and internal keys.