JPS6229333A - System for setting ciphering key - Google Patents

Abstract

PURPOSE:To disperse the danger of ciphering key leakage by preserving a ciphering key while being separated into a generating means and a parameter. CONSTITUTION:In inputting a parameter from a parameter input device 2, the parameter is stored in a parameter storage memory 7 in a ciphering key generating device 3 via a parameter input device adaptor 4 and a ciphering key generating device input/output adaptor 5, a microprocessor 6 in the device 3 executes a ciphering key generation program 8 to generate the ciphering key. The generated ciphering key is stored in a ciphering key storage memory 9 in a confidentiality protecting device 1 via a ciphering key generation input/ output adaptor 5. A ciphering processing device 10 applies ciphering/decoding to the content of a transmission/reception buffer, sends the ciphered key to an opposite party via a line and applies decoding to the reception data. thus, the confidentiality of the ciphering key is improved.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a system for storing an encryption key in a security protection device having a mechanism for cryptographically processing data as a cryptographic key function when performing data security protection. Regarding.

[Background of the invention]

One of the encryption methods for protecting data confidentiality is the DBS algorithm, but since this is known as the US data encryption standard, the strength of the encryption depends on the confidentiality of the encryption key, and the handling of the encryption key is 9, sufficient confidentiality protection is necessary. A known example regarding key security f will be described below.

When constructing an encrypted data communication system using the DES algorithm, it is assumed that a pair of encryption device and decryption device each have the same encryption key, but the encryption key cannot be decrypted by a third party. It is necessary to set this on each device.

Furthermore, if the same encryption key is used for a long period of time, there is a high possibility that the key will be decrypted by a third party, so it is necessary to change it at an appropriate time.

Regarding the above point, that is, the distribution and modification of encryption keys, the concept of master keys and data encryption keys is described in, for example, Japanese Patent Application Laid-open No. 87033/1983. A data encryption key is a cryptographic key for encrypting data on a normal line, and is always handled in encrypted form with the master key, and is only handled in raw form by a specific key that performs cryptographic processing. Only part. Therefore, since it is encrypted with the master key, even if it is sent over the line and transmitted to the other party,
It cannot be easily decrypted by a third party, and keys can be distributed and changed without human intervention. However, even though the data is encrypted with a master key, there is a high risk that the data encryption key could be leaked if the timing of key delivery or changes were discovered. The master key itself needs to be communicated to the other party by some method, such as by telephone, mail, or a portable storage medium such as a flash disk, but in any case, it is carried in some form of memory. If a third party were to read the stored data and obtain the master key, the data used in the system would be easily decrypted because the data encryption key would be decrypted. As mentioned above, to protect the confidentiality of the master key,
It is necessary to select a sufficiently trusted person to distribute and change keys, making human management difficult. In addition, when distributing the master key via a medium, it is necessary to attach a physical key or convert the key and store it so that it cannot be easily read from the medium, which requires the creation of an expensive device. Furthermore, in Japanese Patent Application Laid-Open No. 55-34520, the problem of distribution and change of encryption keys is solved by having a plurality of encryption keys and arbitrarily selecting and using them. In this method, a large number of encryption keys are set in the security device in advance, and the keys are selected based on key specification information when encrypting/decrypting, and when the key is changed, the key itself is hidden from view. It is characterized by the fact that it can be done without touching anything. However, there is no mention of setting a large number of encryption keys yz' in the security device.

Furthermore, in Japanese Patent Application Laid-open No. 55-55585, a plurality of encryption keys having different values are automatically generated based on a fixed number of key inputs, and this encryption key is updated by a suitable means to change the key. is facilitated. Even with this method,
Since the cryptographic key to be generated is determined by inputting the key constant, the key constant itself needs to be protected. In this case, since the security device itself has an encryption key generation logic, once the device itself is disassembled and the encryption key generation logic is deciphered, all the encryption keys can be known just by knowing the key constant. Furthermore, if the encryption key generation logic is stolen, the logic cannot be changed because it is built into the device itself, resulting in the encryption keys of all devices being leaked.
This would affect the entire system, so it would be necessary to attach a physical key to the device itself, making the device itself very expensive.

[Purpose of the invention]

An object of the present invention is to provide a security protection system for an encryption key stored in a security protection device when using an encryption system in which the encryption key and decryption key are the same, such as the DBS algorithm.

[Summary of the invention]

The present invention further strengthens the security of the encryption key by providing a means for generating an encryption key in a portable device other than the security device, and providing a means for inputting parameters necessary for the generation. That's true. In other words, the correct encryption key cannot be obtained unless the correct parameters are entered into the specified encryption key generation means, so even if a third party obtains the encryption key generation device and decrypts it, the parameters will not be known. Therefore, it is not possible to generate an encryption key. Further, even if the encryption key generation parameter is leaked, it has no meaning because it is not an encryption key. As described above, the present invention is characterized in that the risk of encryption key leakage is dispersed by storing the encryption key separately in the means for generating it and the parameters.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. In the embodiment, it is composed of a security protection device 1, a parameter input device 2, and an encryption key generation device 6, and performs security protection by encrypting/decrypting data in a transmitting/receiving puff 7111 in the security protection device 1. be. The parameter input device 2 is a keyboard, and the encryption key generation device is a card with a processor, that is, an IC card. The IC card has a microprocessor 6, an encryption key generation program 8, and a parameter storage memory 7.

The operation will be explained below. First, when parameters are input from the parameter input device 2, the parameter input device adapter 4. Parameter storage memory 7 in the encryption key generation device 3 via the encryption key generation device input/output adapter 5
is memorized. Once the parameters are stored, the microprocessor 6 in the encryption key generation device 6 executes the encryption key generation program 8 to generate an encryption key. The encryption key generation program is a program that generates unique data when parameters are given as initial values. The generated encryption key is stored in the encryption key storage memory 9 in the security device 1 via the encryption key generation device input/output adapter 5. Thereafter, the cryptographic processing mechanism 10 encrypts/decrypts the contents of the transmission/reception buffer using the cryptographic key stored in the cryptographic key storage memory, and transmits the encrypted data to the other party via the line. , performs decoding processing of received data.

Next, the encryption key generation program will be explained. DBS
The algorithm requires a 56-bit encryption key and the following focus sequence.

(ao, a, , a, ,・・・・・・・・・・・・
Song a5・)□■aH is 0 or 1.

This via array is expressed by the following polynomial.

R(x) e ao ten a, x-4-a, x2+---
-----+a3. x55@Encryption key generation program, find this R(X) from the remainder of the following division.

P (x) = F is ) / G (x) □■ However, division is m
Perform at od 2.

Here, F(x) is a polynomial built into the encryption key generation program, G (X) is a polynomial input from the parameter input device, and P(X) is a quotient. Also F
(x) is a polynomial of degree 55 or higher, and G (X) is a polynomial of degree 55 [Effects of the Invention] According to the present invention, in a security device that encrypts or decrypts data, the encryption key and the decryption key are the same. When using a certain encryption method, the encryption key that must be held by the security device is distributed and held in the encryption key generation means and the parameters given to it, so when setting or changing the encryption key, the encryption key itself is completely hidden from public view. This has the effect of improving the confidentiality of the encryption key because it can be done without touching the encryption key.

Furthermore, if the encryption key generation parameters are delivered from the center system via the line to the terminal device that is reading the encryption key generation device directly, without inputting the encryption key generation parameters manually,
It is possible to change the encryption key.

Furthermore, by using an easily portable medium such as the IC card described in the embodiment, the encryption key generation means can
The generation program can be easily changed, and the confidentiality of the encryption key generation means can be improved. In addition, by changing the encryption key generation program in the IC card for each installation location, even if a third party decrypts the program in the ICC card, the encryption key and its generation method for the entire system will be exposed. Nothing happens.

Also, by changing the encryption key generation program for each device,
When distributing C-cards, even if the parameters of the encryption key generation program are the same, they will be different encryption keys for each device, so the parameters themselves can be used in newspapers, on TV, etc.
It is also possible to make it publicly available and distribute it, such as on the radio.

Furthermore, by repeatedly executing the program multiple times, that is, by executing the encryption key generation program by inputting parameters and treating the resulting encryption key as the next parameter, it is possible to generate multiple encryption keys with only - parameters. Key generation is possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, FIG. 2 is a flowchart for setting an encryption key, FIG. 3 is a flowchart for encryption, and FIG. 4 is a flowchart for decryption. DESCRIPTION OF SYMBOLS 1... Data security protection device, 5... Encryption key generation device, 6... Microprocessor, 7... Parameter storage memory, 9... Encryption key storage memory, 10... Encryption processing mechanism, 11... Sending/receiving backup. Mr. Tannin Masukaki / JX Kawa M Man No. 1 Mouth No. 20

Claims (1)

[Claims] 1. In a security protection device that performs cryptographic processing on data as a function of a cryptographic key, means for generating a cryptographic key that is uniquely determined by parameter input, means for inputting parameters to the cryptographic key generation means, and a generated cipher. 1. A cryptographic key setting method comprising: means for outputting a key; the cryptographic key generating means is separated from a security protection device; and the cryptographic key is generated by inputting parameters to the cryptographic key generating means.