JP3751684B2 - Encrypted information decryption method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, the encryption of the encryption information mounted on a storage medium such as a CD-ROM or the encryption information sent from the information supplier device is first released from the confidentiality of the personal key, and the information encryption obtained by the release is released. The present invention relates to a method for decrypting with an encryption key .
[0002]
[Prior art]
When selling software, there is a risk that it will be duplicated by the copy function of the installed computer device and illegally used by others by means of floppy disks, communication, and the like. Therefore, in general, software is encrypted and decrypted with password information, etc., or when software is driven, it operates if there is specific secret information, and it cannot be replicated by an access control function that cannot operate without it. Has been done.
[0003]
However, since the software main body is often produced in the form of mass duplicating the same product, as represented by a CD-ROM medium, the secret information such as password information is also the same. there were.
Therefore, even in the case of mass-replicated information, in order not to make the secret information that can be used the same, the information that combines the secret information and the user (user) information to be used is encoded. Distributed. As a result, even if confidential information is disseminated, it can be known from which user it was leaked.
[0004]
That is, as shown in FIG. 2A (1), when the user U2 wants to receive information supply, the user U2 first sends the identifier IDu2 to the information provider P1. The supplier P1 confirms the identity of the user 2 and confirms the identity of the user 2 by, for example, a digital authentication method. If the identity is certain, the connection between the user identifier IDu2 and the key DK used for encrypting the supply information is performed using the key K1. Encrypt and personal key Ku2 = eK1 (IDu2‖DK)
And sends this personal key Ku2 to the user U2. The user U2 stores the key Ku2 in the key storage unit 11 (FIG. 2B).
[0005]
When the user U2 receives the information, as shown in FIG. 2A (2), his / her personal key Ku2 is input to the personal key encrypted information access means provided by the information supplier P1. The encrypted information access means 12 decrypts the personal key Ku2 with K1, and dK1 (Ku2) = IDu2‖DK
Using the information encryption key DK, the encrypted information from the encryption medium 13 such as a CD-ROM is decrypted, and the target information is provided to the user U2. In other words, the software is executed and displayed. If IDu2‖DK is not obtained in the decryption process of the personal key Ku2, it is determined that the access is from another user, and the encrypted media 13 is not accessed.
[0006]
In order to use the encrypted information in this way, the user U2 needs to use secret information unique to that person, that is, the personal key Ku2, and this secret information differs depending on each user, so other users can use it without permission. Can not. Even if the user U2 distributes the secret information (Ku2) to a third party, the supplier P1 decrypts the key Ku2 with the key K1, and uses the identifier IDu2 to determine the user U2 that is the distribution source of the key Ku2. I can know.
[0007]
However, if the key Ku2 is used in a limited group, there is still a risk of unauthorized use. Also, when using simple encoding, there was a risk of generating a key for illegal distribution. For example, when the secret key cryptosystem is adopted as the encryption, since the decryption process should be performed in the software main body, there is a risk of being analyzed by including the analysis subject in the software main body. When this analysis is performed, secret information (personal key) corresponding to the fictitious user can be generated.
[0008]
That is, as shown in FIG. 2A (3), when a person who has obtained the personal key Ku2 can analyze the inside of the encrypted information access means 12 and discover the key K1, the key DK is also used with the key K1. Therefore, the connection between the identifiers IDux and DK of the fictitious user Ux is encrypted with the key K1, and the fictitious personal key Ku3 = eK1 (IDuxｕDK)
Then, the unauthorized user inputs this Ku3 to the encrypted information access means 12 as shown in FIG. 2A (4), whereby the encrypted information is decrypted and supplied to the unauthorized user.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a person with evidence of fraud even when confidential information using software is distributed in order to limit unauthorized use. Moreover, even if analyzed, it is an object of the present invention that secret information that matches the use of software cannot be easily created.
[0010]
[Means for Solving the Problems]
In the present invention, a private key Ku2 in which the connection between the identifier IDu2 of the user U2 and the information encryption key DK is concealed is stored in the Ku2 storage means of the user device of the user U2,
When decrypting information (hereinafter referred to as encrypted information) recorded on a storage medium such as a CD-ROM or encrypted with the information encryption key DK transmitted from an information provider device such as a server,
The user device extracts the personal key Ku2 from the Ku2 storage means, releases the concealment of the personal key Ku2 by the DK setting means, obtains the connection between the identifier and the information encryption key, and uses the obtained information encryption key to assumes row cormorants encrypted information decoding method by the decoding processing unit to decrypt the encrypted information,
[0011]
In particular, the personal key Ku2 is obtained by decrypting the concatenation of the identifier IDu2 and the information encryption key DK with the secret key SK1 of the information provider device in the public key cryptosystem.
The DK setting means performs an encryption process on the personal key Ku2 with the public key PK1 of the information provider apparatus in the public key cryptosystem to obtain a connection between the identifier and the information encryption key.
[0012]
In the public key cryptosystem, data A can be encrypted with the public key PK to obtain encrypted data C = ePK (A), and decryption can be processed with the private key SK to obtain dSK (C) = A. even can encrypt C = e PK (a) and know the PK and, to produce the a from the secret information C, it is necessary secret key SK, can not be inferred from other parameters There is a nature.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In this case as well, as described in the section of the prior art, whether the information encrypted with the encryption key DK (encrypted information) is delivered to the user by a mass-produced storage medium such as a CD-ROM, It is assumed that a user can access information encrypted with the encryption key DK through a server or the like, that is, a database of encrypted information (for example, software) can be accessed through personal computer communication, for example. In addition, the public key PK1 is made public among the public key PK1 and the secret key SK1 forming a pair in the public key cryptosystem.
[0014]
As shown in FIG. 1A (1), the user U2 who wants to receive information provides the identifier IDu2 to the information provider P1. After the information provider P1 confirms the validity of the user U2, the information provider P1 secretly manages the concatenation of the identifier IDu2 and the key DK used to encrypt the encrypted information. The decryption process is performed to generate a personal key Ku2.
[0015]
Ku2 = dSK1 (IDu2‖DK)
This personal key Ku2 is sent to the user U2.
The user U2 stores and saves the personal key Ku2 in the key storage unit 11.
When the user U2 is provided with information, as shown in FIG. 1A, the personal key Ku2 is taken out from the storage means 11 and input to the encrypted information access means 12 provided from the information provider P1. The encrypted information access means 12 encrypts the personal key Ku2 input with the public key PK1 provided in advance therein, and ePK1 (Ku2) = IDu2‖DK
Get. Using the encryption key DK, the encrypted information on the encrypted medium 13 is decrypted and provided to the user U2. If the processing results during the encryption process consistent with IDu2‖D K, not access to the encrypted media 13 determines that the access from other users.
[0016]
Since it is configured in this way, the personal key Ku2 is unique to the user U2 , and only a user having a valid personal key can receive provision of encrypted information. Since the secret key SK1 is secretly held by the information provider P1, even if the encrypted information access means 13 is analyzed, the third party uses the private key Kux = dSK1 (IDux‖DK) for the fictitious user identifier IDx. Even if you try to make it, you can't make it. Further, when the personal key Ku2 of the legitimate user U2 is disseminated, the user U2 can be specified by obtaining the user identifier IDu2 by encrypting the personal key Ku2 with the public key PK1 . Also, since the distributed personal key Ku2 does not know the secret key SK1, a private key for a fictional person cannot be generated.
[0017]
【The invention's effect】
As described above, according to the present invention, even if the encrypted information access means is analyzed, only the public key is known, and the secret information (personal key) dSK1 (IDux‖DK) for the fictitious user identifier IDux. It is difficult for a third party to make. On the other hand, when the secret information (personal key) sold is distributed, the user who has distributed it can be specified by obtaining its identifier IDu.
[Brief description of the drawings]
FIG. 1A is a diagram showing a processing flow of a method of the present invention, and B is a block diagram showing a functional configuration of a method to which this method is applied.
FIG. 2A is a diagram showing a processing flow of a conventional method, and FIG. 2B is a block diagram showing a functional configuration of a method to which the conventional method is applied.

Claims (1)

A personal key Ku2 in which the connection between the identifier IDu2 of the user U2 and the information encryption key DK is concealed is stored in the Ku2 storage means of the user device of the user U2,
When decrypting information (hereinafter referred to as encrypted information) recorded on a storage medium such as a CD-ROM or encrypted with the information encryption key DK transmitted from an information provider device such as a server,
The user device extracts the personal key Ku2 from the Ku2 storage means, releases the concealment of the personal key Ku2 by the DK setting means, obtains the connection between the identifier and the information encryption key, and uses the obtained information encryption key. in line cormorant encrypted information decoding method by the decoding processing means decodes the encrypted information,
The personal key Ku2 is obtained by decrypting the concatenation of the identifier IDu2 and the information encryption key DK with the secret key SK1 of the information provider device in the public key cryptosystem.
The DK setting means performs encryption processing on the personal key Ku2 with the public key PK1 of the information provider apparatus in a public key cryptosystem to obtain a connection between the identifier and the information encryption key. Information decoding method.

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