JP4604418B2 - Communication apparatus and communication method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a session key generation method for performing encrypted communication between communication devices when transmitting / receiving highly confidential data or data requiring copyright protection on the Internet.
[0002]
[Prior art]
In recent years, digital content distribution services are spreading on the Internet. When it is necessary to protect the copyright of this digital content, consideration must be given so that content data does not leak illegally on the distribution channel.
[0003]
In general, such content data is delivered after being encrypted on the transmission path. The content purchaser who has encrypted and received the encrypted data can obtain the purchased content data by decrypting the encrypted data. At that time, when using the common key encryption, both the provider and the purchaser must hold the common key for the common encryption. Since this common key is generally generated for each communication session, it is called a session key. The reason that is generated for each session is that if a fraudulent purchaser accesses the device (illegal terminal) that enables fraud and the provider's device (server) and decrypts the session key, the content is fraudulently thereafter. This is because it is possible to continue to obtain data. Therefore, in order to prevent such unauthorized leakage, a session key must be generated in the process of generating a session key after recognizing that it is a correct purchaser, and the session key must be securely shared between the server and the terminal. I must.
[0004]
Hereinafter, a method for sharing a session key between a server and a terminal will be described as a conventional technique.
[0005]
FIG. 10 is a configuration diagram of an information device having session key generation according to the prior art.
[0006]
The overall configuration includes a communication processing unit 101 for communication such as a modem, an input device 102 such as a keyboard and a mouse, a display device 103 for displaying conditions and results for scheduling, a central processing unit (CPU) 104, and The main storage device 105 temporarily stores the program and value being processed, and the secondary storage device 106 stores and stores the program and data being processed. The secondary storage device 106 includes an authentication processing unit 107, an encryption processing unit 108, and a session key generation unit 109.
[0007]
Next, the flow of processing for generating a session key in the prior art will be described with reference to FIGS.
[0008]
FIG. 11 is a flowchart showing an outline up to generation of a session key between a terminal as a communication device and a server.
[0009]
First, server authentication is performed on both sides, followed by terminal authentication. The authentication algorithm is generally the challenge and response method described below. After mutual authentication of the server terminal succeeds, a common session key is generated by both parties, and encrypted communication using the session key is performed.
[0010]
FIG. 12 is a flowchart showing a challenge and response process that is an authentication algorithm. There are two types of authentication: server authentication and terminal authentication. Here, server authentication will be described. In terminal authentication, the same algorithm is used in a form in which the server and the terminal are interchanged, and thus the description is omitted.
[0011]
First, in step 111, a random number is generated inside the terminal. The generated random number is transmitted to the server in step 112. In step 113, in the terminal, the generated random number is calculated by the one-way function G, and the calculation result is set to a value X. Subsequently, on the server side, the same calculation G as the one-way function described above is calculated for the random number received from the terminal (S114, S115), and the value is set to Y. The calculation result Y at the server is transmitted to the terminal (S116), and at the terminal 117, the values of X and Y are collated. If X = Y, it is processed as server authentication success in step 118, and the next processing is terminal authentication. In step 117, if the values of X and Y are different, it is processed as a server authentication failure, and the migration process is stopped. In the same flow, terminal authentication is executed by exchanging the server and the terminal.
[0012]
Next, a method for generating a session key in the prior art will be described with reference to FIG.
[0013]
The session key is generated by the same method on both the terminal and the server. As an example, a process for generating a session key in a terminal will be described. FIG. 13 is a flowchart showing session key processing.
[0014]
First, in step 121, a value X obtained at the time of authentication is obtained. Subsequently, in step 122, common secret information Z held in advance by the server and the terminal is obtained. Next, the session key Ks is calculated by the function F (X, Z) (S123, S124). In this way, a session key is obtained.
[0015]
The above is the flow of the session key generation process in the prior art.
[0016]
[Problems to be solved by the invention]
In the conventional method, when the encryption algorithm is determined by both parties and the session key is generated, it is common to include the data used at the time of authentication in the key data to confirm that it is the correct partner. . However, even in this case, there is a risk that the generated session key may be stolen by unauthorized access at the time of authentication. A generation method is desired.
[0017]
Therefore, as a method for generating a session key, the first object of the present invention is to generate a session key based on information that is known only to the other party by using a previously used session key when generating the key. And
[0019]
[Means for Solving the Problems]
In order to achieve the first object, the session key generation method of the present invention is surely correct by using a session key used in the past when generating a new session key between processing devices performing encrypted communication. A method for generating a session key based on information that only the other party knows can be obtained.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
According to a first aspect of the present invention, the encryption key used by the transmission and reception of a communication processing unit, said the other communication device and encryption data transmitting and receiving another communication device and encryption data An authentication process for comparing whether or not the authentication data received from the other communication device via the communication processing unit and the authentication data of the communication device match the storage unit that stores the first encrypted data generated based on When the authentication data matches the authentication data, an encryption key is generated based on the first encryption data and the authentication data stored in the storage unit, and the authentication data and the encryption key 2 encryption data is generated, the second encryption data is stored in the storage unit as the first encryption data, and the other communication device and the encryption key are used via the communication processing unit. Encrypt data That a data encryption unit, and a communication device which is provided with, among processing apparatus that performs encryption communication by using a session key attempts in the past when a new session key generation, and on the correct partner It has the effect of making it possible to generate a session key based on information that only both can know. In addition, it is possible to obtain a value including authentication information instead of the session key itself, and even if the previous session key leaks, a new session key cannot be obtained with this session key information alone. If it is not a correct partner, it becomes difficult to generate a session key , and a strong session key can be generated.
[0022]
The invention according to claim 2 of the present invention, the data encryption unit is a communication device and generates a second encrypted data by the hash calculation on the basis of the authentication data and the encryption key .
[0023]
The invention according to claim 3 of the present invention is a communication method for performing transmission / reception of encrypted data between a communication device and another communication device , wherein the authentication processing unit transmits the authentication data of the communication device and the other The first step of comparing whether or not the authentication data received from the communication device matches, and the data encryption unit based on the stored first encrypted data and the authentication data when the authentication data matches Generating the encryption key, generating the second encryption data based on the authentication data and the encryption key, storing the second encryption data as the first encryption data, and A second step of encrypting data using the encryption key, and a method for making it possible to generate a session key based on information that is surely known by both the correct partner and the other party Have . In addition, it is possible to obtain a value including authentication information instead of the session key itself, and even if the previous session key leaks, a new session key cannot be obtained with this session key information alone. If it is not a correct partner, it becomes difficult to generate a session key , and a strong session key can be generated.
[0024]
The invention according to claim 4 of the present invention is characterized in that, in the second step, the data encryption unit generates second encrypted data by hash calculation based on the authentication data and the encryption key. Is a communication method.
[0025]
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0026]
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration for carrying out a session key generation method according to Embodiment 1 of the present invention.
[0027]
As a whole configuration, a communication processing unit 1 for communication such as a modem, an input device 2 such as a keyboard and a mouse, a display device 3 for displaying input and results of conditions for performing a schedule, and a central processing unit (CPU) 4, a main storage device 5 that temporarily stores a program and a value being processed, and a secondary storage device 6 that stores and stores the program and calculation results. The secondary storage device 6 includes an authentication processing unit that performs authentication with a communication partner, an encryption processing unit 8 that performs operations of encryption processing and digest generation, a session key generation unit 9, a session key information storage unit 10, and session key switching timing control. Part 11.
[0028]
FIG. 2 shows a processing flow of a challenge and response that is an authentication algorithm. There are two types of authentication: server authentication and terminal authentication. Here, server authentication will be described. In terminal authentication, the same algorithm is used in a form in which the server and the terminal are interchanged, and thus the description is omitted.
[0029]
First, in step 11, a random number is generated inside the terminal. In step 12, the generated random number is encrypted in advance with a common secret key shared between the server and the terminal, and transmitted to the server (S13). In the terminal, the generated random number is calculated by the one-way function G, and the calculation result is set to a value X (S14). Subsequently, the server side decrypts the encrypted random number received from the terminal (S15), performs the same calculation as the one-way function G described above (S16, S17), and sets the value to Y. The calculation result Y at the server is transmitted to the terminal (S18), and the values of X and Y are collated at step 19 at the terminal. In the case of X = Y, it is processed as server authentication success in step 21, and the process proceeds to terminal authentication which is the next process. In step 19, if the values of X and Y are different, it is processed as a server authentication failure, and the migration process is stopped (S20).
[0030]
In the same flow, terminal authentication is executed by exchanging the server and the terminal.
[0031]
As described above, in the present invention, the random number itself used in the challenge and response authentication is encrypted and sent on the transmission line, thereby making it difficult to decipher the relationship between the random number and the one-way function G.
[0032]
Next, the session key generation method of the present invention will be described. FIG. 3 is an explanatory diagram showing a session key generation method.
[0033]
In this method, both terminal servers execute mutual authentication by challenge response, and the authentication information common to both sides generated in the process of mutual authentication and the session key generated last time are calculated by exclusive OR, and the calculation result Is used as a session key. By this method, a common session key cannot be generated unless it is the other party who performed the previous encrypted communication, so that it is more surely the correct party. The processing flow of this method will be described with reference to the flowchart of FIG. Since the same processing is performed on both terminal servers, the processing performed on the terminal side will be described as an example here.
[0034]
First, in step 31, the exclusive logic of Y and Z is calculated based on the verification data Y used for server authentication and the verification data Z used for terminal authentication, and the result is set to AU1. In step 32, the session key KS1 previously generated and stored in advance is extracted from the secondary storage area. Next, in step 33, the exclusive logic of AU1 and KS1 is calculated and the result is KS2. In step 34, KS2 is stored in the primary storage area as session key information for the current encrypted communication. Finally, in step 35, since it is used as the value of KS1 at the next session key generation, it is stored in the secondary storage area, and the session key generation processing ends.
[0035]
The above is the first embodiment of the present invention.
[0036]
(Embodiment 2)
Next, Embodiment 2 will be described with reference to FIGS.
[0037]
Note that the mutual authentication method is the same as that of the first embodiment described with reference to FIG. 2, and only the session key generation method will be described here.
[0038]
FIG. 5 is an explanatory diagram showing a session key generation method.
[0039]
In this method, both terminal servers perform mutual authentication by challenge response, and perform hash operation from the authentication information common to both sides generated in the process of mutual authentication and the information generated based on the session key generated last time. An exclusive OR operation is performed from the generated value, and the operation result is used as a session key. By this method, in addition to the method of the first embodiment, it is possible to obtain a value to which authentication information is added instead of the session key itself. Even if the previous session key is leaked, only the session key information can be used to create a new session. Since a key cannot be obtained, it is difficult to generate a session key unless it is more reliably the correct partner, and it can be said that this is a strong session key generation method. The processing flow of this method will be described with reference to the flowchart of FIG. Since the same processing is performed on both terminal servers, the processing performed on the terminal side will be described as an example here.
[0040]
First, in step 41, based on the verification data Y used for server authentication and the verification data Z used for terminal authentication, the exclusive logic of Y and Z is calculated, and the result is set to AU2. In step 42, the hash value H1 previously generated and stored in advance is extracted from the secondary storage area. In step 43, the exclusive logic of AU2 and H1 is calculated and the result is KS3. In step 44, KS3 is stored in the primary storage area as session key information for the current encrypted communication. Next, in step 45, AU2 and KS3 are combined to perform a hash calculation to obtain a value H2. In step 46, since H2 is used as the value of H1 used at the time of next session key generation, it is stored in the secondary storage area, and the session key generation processing ends.
[0041]
The above is the second embodiment of the present invention.
[0042]
(Embodiment 3)
Next, Embodiment 3 will be described with reference to FIGS.
[0043]
Note that the mutual authentication method is the same as that of the first embodiment described with reference to FIG. 2, and only the session key generation method will be described here.
[0044]
FIG. 7 is an explanatory diagram showing a session key generation method.
[0045]
In this method, both terminal servers perform mutual authentication by challenge response for the first time, generate a session key based on the authentication information common to both sides during the mutual authentication process, and then the next session key. This is a method of generating and storing and using it as the next session key. In the next session key generation, a random number is generated on the terminal side, and a value obtained by performing an exclusive OR operation on the current session key and the random number is used as the next session key. This method can be said to be a strong session key generation method in which even if the authentication is passed this time, the session key cannot be obtained unless it is the other party who performed the previous communication.
[0046]
The processing flow of this method will be described using the flowchart of FIG. Since both terminal servers perform the same process except for random number generation, the process performed on the terminal side will be described as an example here.
[0047]
In addition, the session key generation from the mutual authentication performed for the first time calculates the exclusive logic of Y and Z based on the verification data Y used for server authentication and the verification data Z used for terminal authentication described in the first embodiment. The value AU1 is used as the session key. The flowchart in FIG. 8 is an explanation of session key generation for the first transfer.
[0048]
First, in step 51, the next session key saved in the secondary storage in advance is taken out. In step 52, the session key K4 in the current encrypted communication is stored in the primary storage. Next, in step 53, a random number R is generated on the terminal side. In step 54, the random number R is encrypted and transmitted to the server. In step 55, the exclusive OR of the session key K4 and the random number R is calculated and set as the next session key K5. In step 56, K5 is stored in the secondary storage area, and the session key generation process ends.
[0049]
The above is the third embodiment of the present invention.
[0050]
(Embodiment 4)
Next, a method for randomly switching session keys between server terminals without applying a trigger for switching session keys during encrypted communication will be described.
[0051]
Data conversion F is performed with the session key currently being communicated as input, and the number of communications between both sides (all the number of transmissions / receptions) is validated, the number of communications is counted up, and the calculated number of communications is reached. This is a method in which a session key is generated at both server terminals at the time and used as a session key for subsequent encrypted communication.
[0052]
FIG. 9 is an illustration of this method. First, when 64-bit data is generated, the switching timing is calculated by conversion F based on this key data in both server terminals. Until the calculated value is reached, both sides count up the number of communications, and when the switching timing value (for example, 87 times) is reached, the session key is played back, and similarly converted from the newly generated session key Communication is performed until the switching timing obtained by F. Note that any of the methods described in the first to third embodiments is used as a session key generation method.
[0053]
The above is the fourth embodiment of the present invention.
[0054]
【The invention's effect】
As described above, the communication device according to claim 1 of the present invention uses the session key used in the past between the processing devices that perform encrypted communication at the time of generating a new session key, thereby ensuring the correct counterpart. In addition, an advantageous effect that a session key can be generated by information that only the both can know is obtained.
In addition, it is possible to obtain a value including authentication information instead of the session key itself, and even if the previous session key leaks, a new session key cannot be obtained with this session key information alone. If it is not a correct partner, it is difficult to generate a session key, and a strong session key can be generated.
[0056]
In the communication method according to claim 3 of the present invention, a session key used in the past is used when a new session key is generated between processing devices that perform encrypted communication, so that only the other party can know with certainty. There is an advantageous effect that a session key can be generated with no information.
In addition, it is possible to obtain a value including authentication information instead of the session key itself, and even if the previous session key leaks, a new session key cannot be obtained with this session key information alone. If it is not a correct partner, it is difficult to generate a session key, and a strong session key can be generated.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of the present invention. FIG. 2 is a challenge and response process flowchart in the present invention. FIG. 3 is an explanatory diagram of a session key generation method in a first embodiment of the present invention. Flowchart of processing up to session key in Embodiment 1 FIG. 5 is an explanatory diagram of a session key generation method in Embodiment 2 of the present invention. FIG. 6 is a flowchart of processing up to session key in Embodiment 2 of the present invention. Explanatory diagram of a session key generation method according to the third embodiment of the present invention. FIG. 8 is a processing flowchart up to the session key according to the third embodiment of the present invention. FIG. 9 is an explanatory diagram of key switching timing. FIG. 11 is a block diagram showing a device equipped with the method. FIG. 11 is a schematic diagram of processing of a conventional session key generation method. Management of detailed flowchart 13 EXPLANATION OF REFERENCE NUMERALS detailed flowchart of the conventional session key generation process
1 Communication Processing Unit 2 Input Device 3 Display Device 4 Central Processing Unit (CPU)
5 Main storage device 6 Secondary storage device 7 Authentication processing unit 8 Encryption processing unit 9 Session key generation unit 10 Session key information storage unit 11 Session key switching timing control unit

Claims (4)

A communication processing unit that transmits and receives another communication apparatus and encrypted data,
A storage unit for storing the first encrypted data generated on the basis of the encryption key used by the transmission and reception of the is another communication device and encryption data,
An authentication processing unit that compares whether the authentication data received from the other communication device via the communication processing unit matches the authentication data of the communication device ;
When the authentication data matches, an encryption key is generated based on the first encryption data stored in the storage unit and the authentication data, and a second encryption based on the authentication data and the encryption key generates data, the causes are stored in the storage unit the second encryption data as the first encrypted data, the data using the encryption key and the another communication apparatus through the communication processing section encryption communication apparatus characterized by comprising: a data encryption unit, the to of. The communication apparatus according to claim 1, wherein the data encryption unit generates second encrypted data by hash calculation based on the authentication data and the encryption key. A communication method for transmitting and receiving encrypted data between a communication device and another communication device,
A first step of the authentication processing unit compares whether the authentication data of the communication device and the authentication data received from the other communication apparatus are matched,
The data encryption unit generates an encryption key based on the stored first encryption data and the authentication data when the authentication data matches, and a second based on the authentication data and the encryption key. It generates the encrypted data, stores the second encryption data as the first encryption data, comprising a second step of encrypting the data using the encryption key and the other communication devices A communication method characterized by the above . 4. The communication method according to claim 3 , wherein, in the second step, the data encryption unit generates second encrypted data by hash calculation based on the authentication data and the encryption key.

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