JP5193924B2 - Cryptographic communication system, administrator device, and program - Google Patents

Description

  The present invention relates to a cryptographic communication system, an administrator device, and a program.

When sending and receiving encrypted electronic information, as a method of ensuring the confidentiality or reliability of electronic information, the sender can issue an electronic certificate signed by a trusted third party, There is a way to prove the authenticity of the electronic information.
In relation to the technology for issuing this electronic certificate, X. ITU-T has formulated X.I.T.T as a standard for a PKI trust model using a public key cryptosystem called a public key certificate. 509 (see Non-Patent Document 1, for example).

Also, as a method of transmitting and receiving electronic information that does not require a public key certificate, there is a certificate-based public encryption method (CBE). In this method, the administrator first sets parameters used in the calculation in the program that generates the key, a specific ID such as an e-mail address of the recipient (the side that receives the encrypted electronic information), a random number, and the like Generate the master secret generated by
Next, the administrator performs conversion of the receiver ID using a conversion value for each predetermined character string, and further sets parameters, a specific ID of the receiver, a master secret, and a key generation program. Use to generate a key (see, for example, Patent Document 1).

Furthermore, in a hierarchical ID-based encryption method using a public encryption key that does not require a public key certificate, the sender obtains an e-mail address that is the public key and the receiver ID from the receiver.
Next, if the e-mail address of the recipient ID is, for example, “alice@cs.univ.edu”, “alice”, “cs”, “univ”, “edu” are set as ID tuples.
Then, the sender combines the public information to be encrypted with the public key and the ID tuple of the receiver ID to generate an encrypted part.
The recipient ID used for the encryption is not converted as in Patent Document 1, but is decomposed into an ID tuple and used. In this method, since the mathematical configuration concept of elliptic curve and pairing is used, the safety of the system is ensured (see, for example, Non-Patent Document 2).

JP 2005-537711 A

Information Security Technology Laboratory, “PKI-related technical explanation (3 certificate authority and electronic certification)”, July 3, 1999, Information Processing Promotion Agency Security Center, [Search February 25, 2009], Internet <http: // www. ipa. go. jp / security / pki / index. html> C. Gentry, A.M. Silverberg “Hierarchical ID-Based Cryptography,” Asiacrypt 2002, 8th International Conference on the Theory and Application of Cryptology and Information. 548-566

In the prior art described in Non-Patent Document 1, a sender who encrypts electronic information using a public key receives a public key certificate and a public key certificate from a trusted public key certification authority in order to ensure the safety of data. It was necessary to check the validity of the public key by issuing a revocation list of the public key.
However, generally, the public key cryptosystem has a problem that the amount of calculation required for performing decryption for verifying the signature is larger than that of the common key cryptosystem.
For this reason, if it is difficult to check the revocation of the public key due to the environment of the terminal used by the sender, it is encrypted using the public key without checking the revocation of the public key and sent to the receiver. However, there is a problem that the safety of the transmitted data is not ensured.

In the case of Patent Document 1 in which public key authentication is not required, the character string of the recipient ID is once converted into binary, and thereafter, conversion parameters corresponding to each predetermined character string are used. This is done by key generation calculation. Therefore, it is necessary to prepare parameters used in the key generation program individually for each user, and the number of parameters that need to be saved increases as the number of users using this method increases.
This parameter is done by selecting one element of the cyclic group from the binary digit string.
For example, if the number of users is 500, 2 ^ 9 = 512, and a vector of elements of a group composed of 9 elements is required. In the case of 10,000 people, 2 ^ 14 = 16384, and a vector of elements of a group composed of 14 elements is required.
Also, since the parameters need to be strictly managed, it is necessary for the administrator side to store them in a safe tamper resistant area on the device. However, the capacity of the tamper resistant area is limited, and the number of parameters to be saved increases as the number of users using this method increases, and there is a problem that the parameters cannot be stored.

Furthermore, in the case of Non-Patent Document 2 in which public key authentication is not required and conversion of the receiver ID is not required, a decryption key that is a secret key is generated and managed by the system management side and acquired by the receiver. There was a need.
For this reason, since system administrators other than the receiver can decrypt the encrypted electronic information, there is an operational problem.

  The present invention has been made in view of the above problems, and makes it unnecessary to issue a sender's public key certificate while ensuring safety, and further reduces the capacity of parameters managed on the administrator side. An object is to provide a system, an administrator device, and a program.

In the present invention, the sender terminal encrypts and transmits electronic information using the receiver public key, and the receiver terminal receives the encrypted electronic information and decrypts it using the receiver private key. In the cryptographic communication system in which the administrator device manages the information on the recipient public key,
The receiver side terminal
A receiver ID generating means for generating a receiver ID including the receiver's unique information and the expiration date of the receiver public key;
Registration request means for requesting the administrator device to register the generated recipient ID;
A key generating means for generating a pair of a receiver public key and a receiver secret key using the generated receiver ID;
Encrypted information receiving means for receiving electronic information encrypted using the receiver public key from the sender terminal;
Decryption ticket requesting means for requesting the administrator device to issue a decryption ticket including information necessary for decryption;
Decryption ticket receiving means for receiving the decryption ticket from the administrator device;
Decryption means for decrypting the encrypted electronic information using the decryption ticket and the recipient private key;
With
The sender terminal is
An encryption means for encrypting electronic information using the recipient public key;
Encrypted information delivery means for delivering the encrypted electronic information to the receiver side terminal;
With
The administrator device is
A receiver ID registration means for registering a receiver ID generated by the receiver terminal and a revocation identifier of a receiver public key corresponding to the receiver ID;
Revocation for setting the revocation identifier of the recipient public key corresponding to the recipient ID to be revoked when an invalidation request is received from the recipient-side terminal for the recipient public key corresponding to the registered recipient ID Setting means;
Validity confirmation accepting means for accepting a request for confirming the validity of the recipient public key from the receiver-side terminal, and obtaining a date and time when a request for confirming the validity of the recipient public key is accepted;
Expiration date extracting means for extracting the expiration date of the recipient public key from the recipient ID;
The expiration date extracted by the expiration date extraction unit is compared with the date and time acquired by the validity check reception unit, and the date acquired by the validity check reception unit is extracted by the expiration date extraction unit. The receiver public key is determined to be within the validity period, and the reception date is obtained when the date and time obtained by the validity confirmation accepting unit is outside the validity period extracted by the validity period extracting unit. Expiration date comparison means for determining that the public key of the user is outside the expiration date;
Referring to a revocation identifier of a recipient public key corresponding to the registered recipient ID according to a request for confirming the validity of the recipient public key;
As a result of the reference by the reference unit, the revocation identifier of the revocation identifier of the recipient public key corresponding to the recipient ID has not been set, and the recipient public key is within the expiration date by the expiration date comparison unit. Means for generating the decryption ticket when it is determined,
Decryption ticket delivery means for delivering the generated decryption ticket to the receiver side terminal;
It is characterized by having.

In the present invention, the manager device is
Parameter generation means for generating common parameters;
Key generation means for generating a key generation program for generating a pair of the recipient public key and the recipient private key using the parameter generated by the parameter generation means;
An encryption program generating means for generating an encryption program for encrypting electronic information using the parameter generated by the parameter generating means;
Decryption program generation means for generating a decryption program for decrypting the encrypted electronic information using the parameter generated by the parameter generation means;
Decryption ticket program generation means for generating a decryption ticket program for generating a decryption ticket including information for decrypting encrypted electronic information using the parameter generated by the parameter generation means;
It is characterized by having.

Furthermore, in the present invention, the sender side terminal encrypts and transmits the electronic information using the receiver public key, and the receiver side terminal receives the encrypted electronic information and receives the receiver private key. Decryption using the administrator device computer in the cryptographic communication system in which the administrator device manages the information on the recipient public key,
A receiver ID registration step of registering a receiver ID generated by the receiver terminal, a receiver ID including an expiration date of the receiver public key, and a revocation identifier of the receiver public key corresponding to the receiver ID; ,
Revocation setting for revoking the revocation identifier of the recipient public key corresponding to the recipient ID when a revocation request is received from the recipient terminal for the recipient public key corresponding to the registered recipient ID Process,
Validity of accepting a request for confirming the validity of the recipient public key generated at the recipient side terminal from the recipient side terminal and acquiring the date and time when the request for confirming the validity of the recipient public key is accepted Confirmation acceptance process,
An expiration date extracting step of extracting an expiration date of the recipient public key from the recipient ID;
The expiration date extracted in the expiration date extraction step is compared with the date acquired in the validity check reception step, and the date acquired in the validity check reception step is extracted in the expiration date extraction step. The receiver public key is determined to be within the expiration date, and the reception date is obtained when the date and time acquired in the validity check reception step is outside the expiration date extracted in the expiration date extraction step. Expiration date comparison step for determining that the public key is outside the expiration date;
Referring to the revocation information of the recipient public key corresponding to the registered recipient ID according to the request for confirming the validity of the recipient public key;
As a result of the reference by the reference means, the revocation identifier of the revocation identifier of the recipient public key corresponding to the recipient ID has not been set, and the recipient public key is within the expiration date by the expiration date comparison step. If it is determined that there is a step of generating the decryption ticket;
A decryption ticket delivery step of delivering the generated decryption ticket to the receiver side terminal;
It is characterized by having.

Furthermore, in the present invention, the sender side terminal encrypts and transmits the electronic information using the receiver public key, and the receiver side terminal receives the encrypted electronic information and receives the receiver private key. In an administrator device used in an encryption communication system that performs decryption using:
A receiver ID registration means for registering a receiver ID generated by the receiver side terminal, a receiver ID including an expiration date of the receiver public key, and a revocation identifier of the receiver public key corresponding to the receiver ID; ,
Revocation setting for revoking the recipient public key revocation identifier corresponding to the recipient ID when a revocation request is received from the recipient side terminal for the recipient public key corresponding to the registered recipient ID Means,
Validity of accepting a request for confirming the validity of the recipient public key generated at the recipient side terminal from the recipient side terminal and acquiring the date and time when the request for confirming the validity of the recipient public key is accepted Confirmation acceptance means;
Expiration date extracting means for extracting the expiration date of the recipient public key from the recipient ID;
The expiration date extracted by the expiration date extraction unit is compared with the date and time acquired by the validity check reception unit, and the date acquired by the validity check reception unit is extracted by the expiration date extraction unit. If the date and time acquired by the validity confirmation accepting unit is outside the expiration date extracted by the expiration date extracting unit, it is determined that the recipient public key is within the expiration date. Expiry date comparison means for determining that the public key is out of expiry date;
Referencing means for referring to the revocation information of the recipient public key corresponding to the registered recipient ID according to the request for confirming the validity of the recipient public key;
As a result of the reference by the reference unit, the revocation identifier of the revocation identifier of the recipient public key including the recipient ID has not been set, and further, the recipient public key is within the expiration date by the expiration date comparison unit. Means for generating the decryption ticket when it is determined,
Decryption ticket delivery means for delivering the generated decryption ticket to the receiver side terminal;
It is characterized by having.

According to the present invention, when electronic information is encrypted using a public key, the sender does not issue a public key certificate before transmission, and the receiver sends the information necessary for decryption to the system administrator. Since the decryption ticket including the decryption ticket is requested and decryption is performed using the decryption ticket, the sender does not have to confirm the revocation.
In addition, when the security of the public key is lost, the system administrator has not issued a decryption ticket, so the received electronic information cannot be decrypted, and the transmitted data can be secured. is there.
Furthermore, since the parameters and programs used for the generation, encryption and decryption of public and private keys have been optimized, it should be stored in comparison with existing authentication systems using PKI even if the number of users increases. Since the number of parameters is small, it is possible to reduce the amount of safe storage area used in the system.

It is the schematic which shows an example of the network structure which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the sender terminal which concerns on the same embodiment. It is a block diagram which shows the structure of the receiver terminal which concerns on the same embodiment. It is a block diagram which shows the structure of the system administrator apparatus which concerns on the same embodiment. It is a flowchart of the authentication method which concerns on the same embodiment. It is a block diagram which shows the structure of the sender terminal which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the receiver terminal which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the system administrator apparatus which concerns on 2nd Embodiment. It is a flowchart of the method of the authentication which concerns on 2nd Embodiment.

[First embodiment]
Hereinafter, the first embodiment of the present invention will be described in detail with reference to FIGS. In addition, this invention is not limited to the embodiment which concerns, A various change is possible within the range of the technical thought.

FIG. 1 is a schematic diagram illustrating an example of a network configuration according to an embodiment of the present invention.
The sender terminal 1 is a terminal used by a sender who encrypts and transmits electronic information using an encryption key (hereinafter referred to as an encryption key) which is a public key.
The recipient terminal 2 is a terminal used by a recipient who receives encrypted electronic information and decrypts it using a decryption key (hereinafter referred to as a decryption key) which is a secret key.
The system management device 3 is a terminal used by a system administrator who performs processing for confirming the validity of an encryption key and issuing a decryption ticket.
The sender terminal 1, the receiver terminal 2, and the system management device 3 are connected to a network 4 such as the Internet separately through a communication line, and transmit / receive data to / from each other.

FIG. 2 is a block diagram showing a configuration of the sender terminal 1.
The sender terminal 1 is a terminal used by the sender, and includes a control unit 101, a network connection unit 102, an encryption key reception unit 103, an encryption execution unit 104, and an encrypted data transmission unit 105. Yes.

  The control unit 101 controls each unit of the network connection unit 102, the encryption key reception unit 103, the encryption execution unit 104, and the encrypted data transmission unit 105.

  The network connection unit 102 is connected to the network 4 and transmits / receives data to / from other terminals.

  The encryption key receiving unit 103 receives and stores the encryption key generated by the receiver terminal 2 from the receiver terminal 2.

    The encryption execution unit 104 encrypts electronic information using the encryption key.

  The encrypted data transmission unit 105 transmits the electronic information encrypted by the encryption execution unit 104 to the recipient terminal 2 via the network 4.

FIG. 3 is a block diagram showing a configuration of the recipient terminal 2.
The receiver terminal 2 is a terminal used by the receiver, and includes a control unit 201, a network connection unit 202, a receiver ID generation unit 203, a key generation unit 204, a receiver ID registration request unit 205, an encryption The encryption key transmission unit 206, the encrypted data reception unit 207, the decryption ticket request unit 208, the decryption ticket reception unit 209, and the decryption unit 210 are provided.

  The control unit 201 includes a network connection unit 202, a recipient ID generation unit 203, a key generation unit 204, a recipient ID registration request unit 205, an encryption key transmission unit 206, an encrypted data reception unit 207, The decryption ticket request unit 208, the decryption ticket reception unit 209, and the decryption unit 210 are controlled.

The network connection unit 202 connects to the network 4 and transmits / receives data to / from other terminals.
Further, the receiver terminal 2 sends a request for issuing a decryption ticket, which will be described later, which is necessary when registering and decrypting the receiver ID, to the system management apparatus 3 via the network connection unit 202. Against.

The recipient ID generation unit 203 generates a recipient ID by combining the identifier of the recipient (for example, an e-mail address, the telephone number of the recipient) with the expiration date of the key to be generated.
For example, if the recipient's email address is alice @ cs. univ. In the case of edu, when the expiration date is set to December 31, 2011, the recipient ID is alice @ cs. univ. It becomes like edu‖201111231.

The key generation unit 204 uses the recipient ID generated by the recipient ID generation unit 203 to generate an encryption key / decryption key pair.
The generated encryption key and decryption key are preferably stored in a secure storage area of the receiver terminal 2 by the receiver.

  The receiver ID registration request unit 205 notifies the system management apparatus 3 of the receiver ID generated by the receiver ID generation unit 203 and requests registration.

  The encryption key transmission unit 206 delivers the encryption key generated by the key generation unit 204 to the sender terminal 1.

  The encrypted data receiving unit 207 receives electronic data encrypted by the sender terminal 1 using an encryption application via the network 4.

  After receiving the encrypted electronic data from the sender terminal 1, the decryption ticket request unit 208 transmits the registered receiver ID to the system management device 3, and includes decryption including information necessary for decryption described later. Make a ticket request.

  The decryption ticket receiving unit 209 receives a decryption ticket including information necessary for decryption issued from the system management apparatus 3 when the encryption key has not expired.

  It should be noted that the request for the decryption ticket performed by the encrypted data receiving unit 207 to the system management apparatus 3 and the reception of the decryption ticket from the system management apparatus 3 are not exchanges by e-mail or the like because prompt processing is required. For example, in real time in the Internet environment.

  The decryption unit 210 uses the decryption ticket received by the decryption ticket reception unit 209 and the decryption key generated by the key generation unit 204 of the receiving terminal 2 to use the encrypted electronic data received by the encrypted data reception unit 207. Decrypt information.

  As described above, the decryption unit 210 cannot perform decryption when the decryption ticket is not available. Therefore, when the information of the encryption key used by the sender terminal 1 at the time of encryption is wiretapped and decrypted. Since the decryption ticket is not issued, it is possible to ensure the safety of the sender's information.

FIG. 4 is a block diagram showing the configuration of the system manager 3 of the system administrator.
The system management device 3 is a system management device used by the system administrator, and includes a control unit 301, a network connection unit 302, a recipient ID registration request receiving unit 303, a recipient ID registration unit 304, and a decryption ticket request. A receiving unit 305, an encryption key validity checking unit 306, a decryption ticket generating unit 307, and a decryption ticket issuing unit 308 are provided.

  The control unit 301 includes a network connection unit 302, a recipient ID registration request reception unit 303, a recipient ID registration unit 304, a decryption ticket request reception unit 305, an encryption key validity confirmation unit 306, and a decryption ticket. The generation unit 307 and the decryption ticket issuing unit 308 are controlled.

The network connection unit 302 is connected to the network 4 such as the Internet via a communication line, and transmits / receives data to / from other terminals.
Further, the system management apparatus 3 receives the application for use of the present cryptographic communication system from the receiver terminal 2 via the network connection unit 302, receives the registration request for the receiver ID, and decrypts the data (described later) necessary for performing the decryption. Receives ticket issuance requests and issues decryption tickets.

The receiver ID registration request receiving unit 303 receives a receiver ID from the receiver terminal 2 and receives a receiver ID registration request.
Further, the receiver ID registration request receiving unit 303 receives an encryption key revocation procedure from the receiver terminal 2 when the encryption key is decrypted by a third party or when the receiver terminal 2 loses the decryption key. The request is received and transferred to the recipient ID registration unit 306.

The receiver ID registration unit 304 registers the receiver ID received from the receiver terminal 2 by the receiver ID registration request receiving unit 303 in the system management apparatus 3 and encrypts the receiver ID in a database (not shown) corresponding to the receiver ID. Save the key with a revocation identifier indicating whether the key has been revoked.
In addition, when the receiver ID registration request receiving unit 303 receives an encryption key revocation procedure request from the receiver terminal 2, the receiver ID registration unit 304 encrypts the encryption key corresponding to the receiver ID registered in the database. Update the revocation identifier of to the revocation status.

  The decryption ticket request reception unit 305 receives a decryption ticket request from the receiver terminal 2.

The encryption key validity confirmation unit 306 extracts the receiver ID of the receiver terminal 2 from the decryption ticket request received from the receiver terminal 2 by the decryption ticket request reception unit 305 and validates the receiver ID from the receiver ID. The expiration date, that is, the expiration date of the encryption key is extracted.
Also, the encryption key validity confirmation unit 306 acquires the date and time when the decryption ticket request reception unit 305 received the decryption ticket request from the recipient terminal 2, and compares it with the expiration date of the extracted encryption key.
As a result of comparing the date and time when the decryption ticket request receiving unit 305 receives the decryption ticket request and the expiration date of the extracted encryption key, when the decryption ticket request is received within the expiration date of the extracted encryption key, It is determined that the encryption key has not yet expired.
On the other hand, as a result of comparing the date and time when the decryption ticket request receiving unit 305 receives the decryption ticket request and the expiration date of the extracted encryption key, the decryption ticket request is issued at the date and time when the expiration date of the extracted encryption key is exceeded. If received, it is determined that the encryption key has expired.
Also, the encryption key validity confirmation unit 306 receives whether or not the revocation procedure has been performed on the encryption key corresponding to the recipient ID related to the decryption ticket request and the revocation identifier is set to the revoked state. It collates with said database which registered person ID.
Next, the encryption key validity confirmation unit 306 determines that the encryption key corresponding to the recipient ID has not yet expired and the revocation identifier has not been set to the revoked state by the revocation procedure. In addition, it is determined that the encryption key of the receiver terminal 2 is valid.
On the other hand, the encryption key validity confirmation unit 306 determines that the encryption key corresponding to the recipient ID has exceeded the expiration date, or if the revocation procedure has been performed and the revocation identifier has been set to revocation. The encryption key of the receiver terminal 2 is determined to be invalid.
When the encryption key validity confirmation unit 306 determines that the encryption key is revoked, the encryption key validity confirmation unit 306 notifies the receiver terminal 2 of the revocation of the encryption key. In this case, the decryption ticket is not issued.

  When the encryption key validity confirmation function 306 determines that the encryption key is valid, the decryption ticket generation unit 307 generates a decryption ticket including information necessary for decryption.

The decryption ticket issuing unit 308 issues the decryption ticket generated by the decryption ticket generation function 307 to the receiver terminal 2.
The decryption ticket request reception unit 305 receives a decryption ticket request from the decryption ticket request unit 208 of the recipient terminal 2, and the decryption ticket issue unit 308 issues a decryption ticket to the decryption ticket reception unit 209 of the receiver terminal 2. Since the processing requires quick processing, it is not exchanged by e-mail or the like, but is performed in real time in the Internet environment, for example.

  The authentication method of this embodiment will be described with reference to the flowchart of FIG.

  The recipient ID generation unit 203 of the recipient terminal 2 generates a recipient ID by associating the unique information such as the recipient's e-mail address with the expiration date of the public key to be generated (S201).

  The recipient ID registration request unit 205 of the recipient terminal 2 delivers the recipient ID registration request together with the generated recipient ID to the recipient ID registration request receiver 303 of the system management device 3 (S202, S301).

  The recipient ID registration unit 304 of the system management device 3 adds a revocation identifier indicating whether or not the encryption key corresponding to the recipient ID has been revoked to a database (not shown) in the system management device 3. Register and save (S302).

  The key generation unit 204 of the receiver terminal 2 generates a pair of an encryption key and a decryption key using the receiver ID (S203).

  The encryption key transmission unit 206 of the receiver terminal 2 passes the generated encryption key to the encryption key reception unit 103 of the sender terminal 1 in response to a request from the sender terminal 1 separately (S101, S204). .

  Next, the encryption execution unit 104 of the sender terminal 1 encrypts the electronic information using the received encryption key (S102).

  The encrypted data transmitting unit 105 of the sender terminal 1 transmits the encrypted electronic information to the encrypted data receiving unit 207 of the receiver terminal 2 (S103, S205).

  Next, the decryption ticket request unit 208 of the recipient terminal 2 requests the decryption ticket to the decryption ticket request reception unit 305 of the system management apparatus 3 (S206, S303).

Next, the encryption key validity checking unit 306 of the system management apparatus 3 refers to the receiver information stored in a storage unit (not shown) in the system management apparatus 3 and refers to the receiver ID.
Further, the encryption key validity checking unit 306 of the system management apparatus 3 extracts the expiration date of the recipient ID, that is, the expiration date of the encryption key from the referenced recipient ID.
Also, the encryption key validity confirmation unit 306 acquires the date and time when the decryption ticket request reception unit 305 received the decryption ticket request from the recipient terminal 2, and compares it with the expiration date of the extracted encryption key.
As a result of comparing the date and time when the decryption ticket request receiving unit 305 receives the decryption ticket request and the expiration date of the extracted encryption key, when the decryption ticket request is received within the expiration date of the extracted encryption key, It is determined that the encryption key has not yet expired.
On the other hand, as a result of comparing the date and time when the decryption ticket request receiving unit 305 receives the decryption ticket request and the expiration date of the extracted encryption key, the decryption ticket request is issued at the date and time when the expiration date of the extracted encryption key is exceeded. If received, it is determined that the encryption key has expired.
Next, whether or not the encryption key validity confirmation unit 306 of the system management apparatus 3 has a revocation identifier of the encryption key corresponding to the receiver ID set in the database (not shown) in the system management apparatus 3. Or collate.
Subsequently, when the encryption key validity confirmation unit 306 of the system management apparatus 3 has not yet exceeded the expiration date, the revocation identifier is not set to the revocation state. The recipient's encryption key is valid.
On the other hand, when the encryption key validity checking unit 306 of the system management apparatus 3 has exceeded the expiration date or the revocation identifier is set to the revocation status If so, it is determined that the recipient's encryption key has expired (S304).

When the encryption key validity check function 306 determines that the encryption key is valid, the decryption ticket generation unit 307 of the system management apparatus 2 generates a decryption ticket including information necessary for decryption (S305).
On the other hand, when the encryption key validity checking function 306 of the system management apparatus 3 determines that the encryption key is invalid, it notifies the receiver terminal 2 of the expiration of the encryption key. In this case, the decryption ticket is not issued.

  The decryption ticket issuing unit 308 of the system management device 3 issues the generated decryption ticket to the decryption ticket receiving unit 209 of the recipient terminal 2 (S207, S306).

  The decryption unit 210 of the recipient terminal 2 is received by the encrypted data reception unit 207 using the decryption ticket received by the decryption ticket reception unit 209 and the decryption key generated by the key generation unit 204 of the reception terminal 2. The encrypted electronic information is decrypted (S208).

[Second Embodiment]
Next, a second embodiment will be described with reference to FIGS. In addition, what has the same function as 1st Example form uses the same number, and abbreviate | omits description.

FIG. 6 is a block diagram illustrating a configuration of the sender terminal 1 according to the second embodiment.
The difference from the first embodiment is an encrypted application receiving unit 401.

  In the encrypted application receiving unit 401, the receiving terminal 2 receives and stores an application for performing encryption (hereinafter, abbreviated as an encrypted application).

FIG. 7 is a block diagram illustrating a configuration of the recipient terminal 2 according to the second embodiment.
The difference from the first embodiment is an application reception unit 501 and an encrypted application transmission unit 502.

  The application receiving unit 501 includes an application that generates an encryption key / decryption key pair (hereinafter abbreviated as a key generation application) generated by the system management apparatus 3 to be described later, an encryption application, and an application that performs decryption (hereinafter, decryption application). Received and saved.

  The encrypted application transmission unit 502 delivers the encrypted application received from the system management apparatus 3 to the receiver terminal 2.

FIG. 8 is a block diagram illustrating a configuration of the system management apparatus 3 according to the second embodiment.
The difference from the first embodiment is a common parameter generation unit 601, an application generation unit 602, and an application transmission unit 603.

  The common parameter generation unit 601 generates common parameters necessary for key generation, encryption, decryption, and decryption ticket generation, and stores them in a secure storage area in the system management apparatus 3.

  The application generation unit 602 generates a key generation application, a decryption application, and an encryption application using the common parameters generated by the common parameter generation unit 601.

  The application transmission function 603 delivers the generated key generation application, decryption application, and encryption application to the receiver terminal 2 that is a user who applied for the use of the encryption communication system.

An authentication method according to the second embodiment will be described with reference to the flowchart of FIG.
First, the common parameter generation unit 601 of the system management device 3 generates a common parameter (S601).

  Next, the application generation unit 602 of the system management apparatus 3 uses the common parameters generated by the common parameter generation unit 601 to generate a key generation application, an encryption application, and a decryption application (S602).

    Hereinafter, S201, S202, S301, and S302 are performed in the same manner as in the first embodiment.

Next, the recipient ID registration unit 303 of the system management device 3 uses a revocation identifier indicating whether or not the encryption key corresponding to the recipient ID has been revoked in a database (not shown) in the system management device 3. Is registered and saved (S302).
The recipient ID registration unit 304 of the system management device 3 selects the generated common parameter for the recipient, and registers and saves it in the system management device 3 together with the recipient ID.

  Next, the application transmission unit 603 of the system management apparatus 3 delivers the generated key generation application, encryption application, and decryption application to the application reception function 501 of the receiver terminal 2 (S501, S603).

  The receiver's key generation unit 204 generates a pair of an encryption key and a decryption key using the key generation application received by the application reception unit 501 and the receiver ID generated by the receiver ID generation unit 203 ( S203).

  Hereinafter, S101 and S204 are performed in the same manner as in the first embodiment.

  Next, the encrypted application reception function 401 of the sender terminal 1 receives the encrypted application from the encrypted application reception function 501 of the receiver terminal 2 (S401, S502).

  Hereinafter, S103, S205, S206, S303, and S304 are performed in the same manner as in the first embodiment.

The encryption key validity confirmation unit 306 extracts the receiver ID of the receiver terminal 2 from the decryption ticket request received from the receiver terminal 2 by the decryption ticket request reception unit 305 and validates the receiver ID from the receiver ID. The expiration date, that is, the expiration date of the encryption key is extracted.
Also, the encryption key validity confirmation unit 306 acquires the date and time when the decryption ticket request reception unit 305 received the decryption ticket request from the recipient terminal 2, and compares it with the expiration date of the extracted encryption key.
As a result of comparing the date and time when the decryption ticket request receiving unit 305 receives the decryption ticket request and the expiration date of the extracted encryption key, when the decryption ticket request is received within the expiration date of the extracted encryption key, It is determined that the encryption key has not yet expired.
On the other hand, as a result of comparing the date and time when the decryption ticket request receiving unit 305 receives the decryption ticket request and the expiration date of the extracted encryption key, the decryption ticket request is issued at the date and time when the expiration date of the extracted encryption key is exceeded. If received, it is determined that the encryption key has expired.
Also, the encryption key validity confirmation unit 306 receives whether or not the revocation procedure has been performed on the encryption key corresponding to the recipient ID related to the decryption ticket request and the revocation identifier is set to the revoked state. It collates with said database which registered person ID.
Next, the encryption key validity confirmation unit 306 determines that the encryption key corresponding to the recipient ID has not yet expired and the revocation identifier has not been set to the revoked state by the revocation procedure. In addition, it is determined that the encryption key of the receiver terminal 2 is valid.
On the other hand, the encryption key validity confirmation unit 306 is set when the encryption key corresponding to the recipient ID has expired or when the revocation procedure has been performed and the revocation identifier is set to the revoked state. In this case, it is determined that the encryption key of the recipient terminal 2 has expired.
When the decryption ticket generation unit 307 of the system management apparatus 2 determines that the encryption key is valid by the encryption key validity check function 306, the decryption ticket includes information necessary for decryption using the generated common parameter. Is generated (S305).
On the other hand, when the encryption key validity confirmation function 307 of the system management apparatus 3 determines that the encryption key is invalid, it notifies the recipient terminal 2 of the expiration of the encryption key. In this case, the decryption ticket is not issued.

  Hereinafter, since it is performed in the same manner as the first embodiment, the description thereof is omitted.

Next, common parameters will be described by taking a key generation application as an example.
First, the system management device 3 generates a plurality of common parameters from prime numbers, for example.
Next, after the procedure for using the cryptographic communication system is performed from the receiver terminal 2, several parameters are selected from the generated common parameters. The selected parameter is, for example, a group of several constants.
Here, it is assumed that the selected parameter used for the key generation application is g.

  The system management device 3 uses the selected parameter g,

Generate an arithmetic expression. In this case, the ID is a receiver ID generated by the receiver ID generation unit 203 of the receiver terminal 2.
Also,

  Is

  And in this case

Is calculated.
Next, the recipient ID

  Expand like this.

  The application generation unit 601 of the system management apparatus 3 generates a key generation application by combining the above encryption key generation formula and the encryption key generation formula that is not described here.

In the above, the receiver ID is received by combining the receiver identifier (for example, e-mail address, receiver telephone number) with the expiration date of the key to be generated, as in the first embodiment. The receiver ID is generated by the ID generation unit 203 of the receiver terminal 2.
For example, if the recipient's email address is alice @ cs. univ. In the case of edu, when the expiration date is set to December 31, 2011, the recipient ID is alice @ cs. univ. It becomes like edu‖201111231.
The application reception unit 501 of the recipient terminal 2 generates an encryption key / decryption key pair using the key generation application received from the application generation unit 602 of the system management apparatus 3 and the generated recipient ID.

  Thus, in the generation of the encryption key, the parameters used in this embodiment are composed of elements of a group of individual constants generated in advance by the system administrator, so the encryption communication system of this embodiment is used. Even if the number of users increases, it is possible to suppress the storage capacity because the number is small compared to the number of conversion parameters and the storage capacity used for the conversion of the recipient ID of the prior art.

  In the present embodiment, a method for delivering a decryption ticket including information necessary for decryption from the system management device 3 to the recipient terminal 2 without encryption has been described. However, a separate general encryption method, For example, the encrypted data may be transferred using an RSA (Rivest Shamir Adleman) method.

  In this embodiment, an example in which an e-mail address is used as unique information of the receiver when generating the receiver ID has been described. However, as long as it is reliable information that can be confirmed between the receiver and the sender For example, the telephone number or nickname of the recipient may be used.

  Furthermore, in the second embodiment, the decryption ticket application is performed at the time of generating the key generation application in the system management apparatus 3, but it is generated after receiving the decryption ticket request from the decryption ticket request unit 208 of the recipient terminal 2. Anyway.

According to the present invention, since the revocation confirmation of the public key is performed on the receiver side, the burden of issuing the public key certificate on the sender side is reduced, and the decryption ticket including information necessary for the decryption on the receiver side Since the information is obtained and decrypted, the security of information can be secured.
In addition, when generating a key generation application and an encryption / decryption application, the recipient ID is converted into a unique value without converting it into a value determined for each character after binarizing the recipient ID once. Information and parameters generated in advance by the system administrator are used in common. For this reason, the parameters used in each application are reduced, and the usage amount of the safe storage area on the system management side is also reduced, which is beneficial to the user side and the administrator.

DESCRIPTION OF SYMBOLS 1 ... Sender terminal 2 ... Receiver terminal 3 ... System management apparatus 4 ... Network 101, 201, 301 ... Control part 102, 202, 302 ... Network connection part 103 ... Encryption key receiving unit 104 ... Encryption execution unit 105 ... Encrypted data transmission unit 203 ... Recipient ID generation unit 204 ... Key generation unit 205 ... Recipient ID registration request unit 206 ... Encryption key transmission unit 207 ... Encryption data reception unit 208 ... Decryption ticket request unit 209 ... Decryption ticket reception unit 210 ... Decryption unit 303 ... Receiver ID registration request reception unit 304 ... Receiver ID registration unit 305 ... Decryption ticket request reception unit 306 ... Encryption key validity confirmation unit 307 ... Decryption ticket generation unit 308 ... Decryption ticket issue unit 401 ... Encryption Publication receiver 501 ... Application receiving section 502 ... encryption application transmitting section 601 ... common parameter generation section 602 ... application generation unit 603 ... Application transmitting section

Claims (4)

The sender side terminal encrypts and transmits the electronic information using the receiver public key, and the receiver side terminal receives the encrypted electronic information and decrypts it using the receiver private key for management. In the cryptographic communication system in which the receiver device manages the information on the recipient public key,
The receiver side terminal
A receiver ID generating means for generating a receiver ID including the receiver's unique information and the expiration date of the receiver public key;
Registration request means for requesting the administrator device to register the generated recipient ID;
A key generating means for generating a pair of a receiver public key and a receiver secret key using the generated receiver ID;
Encrypted information receiving means for receiving electronic information encrypted using the receiver public key from the sender terminal;
Decryption ticket requesting means for requesting the administrator device to issue a decryption ticket including information necessary for decryption;
Decryption ticket receiving means for receiving the decryption ticket from the administrator device;
Decryption means for decrypting the encrypted electronic information using the decryption ticket and the recipient private key;
With
The sender terminal is
An encryption means for encrypting electronic information using the recipient public key;
Encrypted information delivery means for delivering the encrypted electronic information to the receiver side terminal;
With
The administrator device is
A receiver ID registration means for registering a receiver ID generated by the receiver terminal and a revocation identifier of a receiver public key corresponding to the receiver ID;
Revocation for setting the revocation identifier of the recipient public key corresponding to the recipient ID to be revoked when an invalidation request is received from the recipient-side terminal for the recipient public key corresponding to the registered recipient ID Setting means;
Validity confirmation accepting means for accepting a request for confirming the validity of the recipient public key from the receiver-side terminal, and obtaining a date and time when a request for confirming the validity of the recipient public key is accepted;
Expiration date extracting means for extracting the expiration date of the recipient public key from the recipient ID;
The expiration date extracted by the expiration date extraction unit is compared with the date and time acquired by the validity check reception unit, and the date acquired by the validity check reception unit is extracted by the expiration date extraction unit. If the recipient public key is determined to be within the expiration date, and the date and time acquired by the validity confirmation accepting unit is outside the expiration date extracted by the expiration date extraction unit,
Expiration date comparison means for determining that the recipient public key is outside the expiration date;
Referring to a revocation identifier of a recipient public key corresponding to the registered recipient ID according to a request for confirming the validity of the recipient public key;
As a result of the reference by the reference unit, the revocation identifier of the revocation identifier of the recipient public key corresponding to the recipient ID has not been set, and the recipient public key is within the expiration date by the expiration date comparison unit. Means for generating the decryption ticket when it is determined,
Decryption ticket delivery means for delivering the generated decryption ticket to the receiver side terminal;
A cryptographic communication system comprising: The administrator device is
Parameter generation means for generating common parameters;
Key generation means for generating a key generation program for generating a pair of the recipient public key and the recipient private key using the parameter generated by the parameter generation means;
An encryption program generating means for generating an encryption program for encrypting electronic information using the parameter generated by the parameter generating means;
Decryption program generation means for generating a decryption program for decrypting the encrypted electronic information using the parameter generated by the parameter generation means;
Decryption ticket program generation means for generating a decryption ticket program for generating a decryption ticket including information for decrypting encrypted electronic information using the parameter generated by the parameter generation means;
The cryptographic communication system according to claim 1, further comprising: The sender side terminal encrypts and transmits the electronic information using the receiver public key, and the receiver side terminal receives the encrypted electronic information and decrypts it using the receiver private key for management. A computer of the administrator device in the cryptographic communication system in which the administrator device manages the information on the recipient public key,
A receiver ID registration step of registering a receiver ID generated by the receiver terminal, a receiver ID including an expiration date of the receiver public key, and a revocation identifier of the receiver public key corresponding to the receiver ID; ,
Revocation setting for revoking the revocation identifier of the recipient public key corresponding to the recipient ID when a revocation request is received from the recipient terminal for the recipient public key corresponding to the registered recipient ID Process,
Validity of accepting a request for confirming the validity of the recipient public key generated at the recipient side terminal from the recipient side terminal and acquiring the date and time when the request for confirming the validity of the recipient public key is accepted Confirmation acceptance process,
An expiration date extracting step of extracting an expiration date of the recipient public key from the recipient ID;
The expiration date extracted in the expiration date extraction step is compared with the date acquired in the validity check reception step, and the date acquired in the validity check reception step is extracted in the expiration date extraction step. The receiver public key is determined to be within the expiration date, and the reception date is obtained when the date and time acquired in the validity check reception step is outside the expiration date extracted in the expiration date extraction step. Expiration date comparison step for determining that the public key is outside the expiration date;
Referring to the revocation information of the recipient public key corresponding to the registered recipient ID according to the request for confirming the validity of the recipient public key;
As a result of the reference by the reference means, the revocation identifier of the revocation identifier of the recipient public key corresponding to the recipient ID is not set, and the recipient public key is within the expiration date by the expiration date comparison step. A step of generating the decryption ticket when it is determined,
A decryption ticket delivery step of delivering the generated decryption ticket to the receiver side terminal;
An encryption communication program for executing Cryptographic communication in which the sender terminal encrypts and transmits electronic information using the receiver public key, and the receiver terminal receives the encrypted electronic information and decrypts it using the receiver private key In the administrator device used in the system,
A receiver ID registration means for registering a receiver ID generated by the receiver side terminal, a receiver ID including an expiration date of the receiver public key, and a revocation identifier of the receiver public key corresponding to the receiver ID; ,
Revocation setting for revoking the recipient public key revocation identifier corresponding to the recipient ID when a revocation request is received from the recipient side terminal for the recipient public key corresponding to the registered recipient ID Means,
Validity of accepting a request for confirming the validity of the recipient public key generated at the recipient side terminal from the recipient side terminal and acquiring the date and time when the request for confirming the validity of the recipient public key is accepted Confirmation acceptance means;
Expiration date extracting means for extracting the expiration date of the recipient public key from the recipient ID;
The expiration date extracted by the expiration date extraction unit is compared with the date and time acquired by the validity check reception unit, and the date acquired by the validity check reception unit is extracted by the expiration date extraction unit. If the date and time acquired by the validity confirmation accepting unit is outside the expiration date extracted by the expiration date extracting unit, it is determined that the recipient public key is within the expiration date. Expiry date comparison means for determining that the public key is out of expiry date;
Referencing means for referring to the revocation information of the recipient public key corresponding to the registered recipient ID according to the request for confirming the validity of the recipient public key;
As a result of the reference by the reference unit, the revocation identifier of the revocation identifier of the recipient public key including the recipient ID has not been set, and further, the recipient public key is within the expiration date by the expiration date comparison unit. Means for generating the decryption ticket when it is determined,
Decryption ticket delivery means for delivering the generated decryption ticket to the receiver side terminal;
An administrator device comprising:

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