JP2010166265A - Information processor, information processing method, and information processing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely protect a secret key and to decrypt encrypted information. <P>SOLUTION: A key information conversion device 500 is provided with: a key storing part 520 for associating a public key certificate for conversion with a secret key corresponding to the public key certificate for conversion to store them; an acquiring part 510 for acquiring key information for conversion including a common key encrypted with the public key certificate for conversion, and a new public key certificate within an expiration date as a public key of a message decryption device 400 from the message decryption device 400 connected through a network; a decrypting part 530 for decrypting common key information included in the otained key information for conversion; an encrypting part 540 for encrypting the decrypted common key information with the new public key certificate, and generating new key information based on the new public key certificate within the expiration date; and an outputting part 570 for outputting the new key information to the message decryption device 400. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an information processing apparatus, an information processing method, and an information processing system for encrypting and decrypting information.

  In the information society in recent years, the development of encryption technology for preventing eavesdropping and falsification of information by a third party is remarkable. One of the encryption platforms is PKI (Public Key Infrastructure).

  The public key encryption technique using PKI is usually used together with the encryption technique of the common key encryption method. The sender generates an encrypted message obtained by encrypting the message to be encrypted (plain text) using the common key encryption method, and generates an encrypted common key obtained by encrypting the common key with the receiver's public key. . Then, the generated encrypted common key and encrypted message are transmitted to the receiver as an encrypted object. The receiver decrypts the encrypted common key with the secret key corresponding to the public key obtained by encrypting the encrypted common key included in the received encrypted object, extracts the common key, and encrypts the message with the extracted common key. Is decrypted.

  Due to the nature of the public key encryption method, the recipient's private key described above is securely stored in a storage medium with physical tamper resistance so that a third party cannot retrieve the private key. In addition to management, a copy of the private key is deposited with a trusted third party in case of eavesdropping or loss (key escrow).

  For example, in Patent Document 1, a common key for encrypting a message shared by a plurality of members is encrypted by generating an encrypted common key obtained by encrypting the public key of each member. A technique for decrypting an encrypted common key with a secret key (secret key) of each member acquired from a person organization (storage device) is disclosed.

  However, in the technology of Patent Document 1, depending on the security level of the third party organization, if the secret key is not securely stored or the communication between the recipient and the third party organization is weak, There is a risk that the information will be leaked when the receiver sends the secret key to the third party. Therefore, a technique for setting an expiration date for a public key certificate has been proposed. However, when the expiration date is set in the public key certificate, there is a problem that the encrypted content cannot be confirmed when the expiration date has expired.

  The present invention has been made in view of the above, and can acquire key information encrypted with a public key certificate whose validity period is valid even when the validity period of the public key certificate has expired. Therefore, it is an object to provide an information processing apparatus, an information processing method, and an information processing system that can extract a common key and decrypt an encrypted message.

  In order to solve the above-described problems and achieve the object, the present invention provides a first information processing apparatus connected to a decryption apparatus for decrypting a message encrypted with a common key via a communication network. A public key and a secret key corresponding to the first public key are stored in association with each other, key information including a common key encrypted with the first public key, and the decryption An acquisition unit that acquires a second public key within the validity period as a public key of the encryption device, and the common key included in the acquired key information is stored in the key storage unit. Decryption means for decrypting with a secret key corresponding to the public key of the user, and encrypting the decrypted common key with the second public key, and generating new key information with the second public key within the expiration date Encrypting means, and the new means generated by the encrypting means Information, characterized in that it comprises and output means for outputting to the decoding device.

  The present invention is also an information processing method executed by an information processing apparatus connected via a communication network to a decryption apparatus that decrypts a message encrypted with a common key, wherein the information processing apparatus comprises: Key storage means for storing a first public key and a private key corresponding to the first public key in association with each other, and the obtaining means obtains a common key encrypted with the first public key. An acquisition step of acquiring the key information including the second public key within the validity period as the public key of the decryption device, and the decryption unit includes the common key included in the acquired key information, A decryption step of decrypting with a secret key corresponding to the first public key stored in the key storage means; and an encryption means encrypting the decrypted common key with the second public key, and an expiration date Generate new key information using the second public key An encryption step that the output means, a new said key information generated in the encryption step, and having and an output step of outputting to the decoding device.

  The present invention also provides an information processing system in which an encryption processing device for encrypting a message, a decryption processing device for decrypting the encrypted message, and an information processing device are connected via a communication network. The encryption processing device encrypts the message using the common key, encrypts the common key using the first public key provided from the information processing device, and is provided from the decryption device. An encryption means for encrypting a common key using a third public key; the encrypted message; conversion key information including the common key encrypted with the first public key; Communication means for transmitting to the decryption processing device key information including the common key encrypted with a third public key, the decryption device including the encrypted message, and the conversion Key information and the third information The key information encrypted with the open key is received, and when the valid period in which the third public key can be decrypted has passed, the second public key within the valid period in which the decryption is possible, and Communication means for transmitting conversion key information to the information processing apparatus and receiving new key information including the common key encrypted with the second public key from the information processing apparatus; and the information processing apparatus Decrypting the new key information received from the private key corresponding to the second public key to obtain the common key, and decrypting the message with the common key, and The information processing apparatus includes: a key storage unit that stores the first public key and a secret key corresponding to the first public key in association with each other; the conversion key information; Obtaining means for obtaining the second public key from the decryption processing device; Decryption means for decrypting the common key included in the acquired conversion key information with a secret key corresponding to the first public key stored in the key storage means; and decrypting the common key An encryption unit that encrypts with the second public key and generates new key information with the second public key within the validity period, and the decryption unit generates the new key information generated by the encryption unit. Output means for outputting to the conversion device.

  According to the present invention, the decryption processing device can acquire key information encrypted with the second public key within the valid period even when the decryption cannot be performed because the valid period has expired. The key can be taken out and the encrypted message can be decrypted.

FIG. 1 is a block diagram showing the configuration of the information processing system according to the present embodiment. FIG. 2 is a block diagram showing a functional configuration of the key / certificate issuing apparatus shown in FIG. FIG. 3 is a block diagram showing a functional configuration of the certification medium shown in FIG. FIG. 4 is a diagram illustrating an example of the public key certificate and the private key stored in the storage unit illustrated in FIG. FIG. 5 is a block diagram showing a functional configuration of the message encryption apparatus shown in FIG. FIG. 6 is a diagram illustrating an example when the encryption unit illustrated in FIG. 5 encrypts the message stored in the storage unit. FIG. 7 is a block diagram showing a functional configuration of the message decoding apparatus shown in FIG. FIG. 8 is a diagram showing the concept of information stored in the storage unit shown in FIG. FIG. 9 is a diagram illustrating an example in which the storage unit illustrated in FIG. 3 stores the new public key certificate and the new public key in association with each other. FIG. 10 is a diagram illustrating a state in which the storage unit illustrated in FIG. 7 further stores a new public key certificate. FIG. 11 is a block diagram showing a functional configuration of the key information conversion apparatus shown in FIG. FIG. 12 is a diagram illustrating a state in which the key storage unit illustrated in FIG. 11 stores the conversion public key and the conversion secret key in association with each other. FIG. 13 is a diagram showing an outline in the case where various types of data are exchanged between the message decryption apparatus and the key information conversion apparatus. FIG. 14A is a sequence diagram illustrating a processing procedure from when a private key and a public key certificate are issued until key information including a public key certificate whose validity period has expired is updated. FIG. 14B is a sequence diagram illustrating a processing procedure from when the private key and the public key certificate are issued until the key information including the public key certificate whose expiration date has expired is updated. FIG. 15 is a diagram illustrating a modification of the information processing system according to the present embodiment.

  Exemplary embodiments of an information processing apparatus, an information processing method, and an information processing system according to the present invention will be explained below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram of an information processing system 1000 according to the present embodiment. As shown in the figure, the information processing system 1000 includes a key / certificate issuing device 100, a certification medium 200, a message encryption device 300, a message decryption device 400, a key information conversion device 500, and communication. Network 600.

  The communication network 600 is a wide area communication line such as the Internet or a WAN (Wide Area Network).

  The key / certificate issuing device 100 issues a public key certificate and a certificate authority for issuing a private key corresponding to the public key certificate to the owner of the message decryption device 400 or the key information conversion device 500 ( It is a server device that plays the role of Certification Authority and Registration Authority.

  FIG. 2 is a block diagram showing a functional configuration of the key / certificate issuing device 100. As shown in FIG. 2, the key / certificate issuing device 100 includes a key generation unit 110, a certificate generation unit 120, a key generation unit 130, a storage unit 140, a communication unit 150, an interface unit 160, It is comprised including.

  The communication unit 150 includes a communication interface such as a network board and controls communication. The communication unit 150 mediates communication between the key / certificate issuing device 100 and the key information conversion device 500.

  The interface unit 160 is an interface such as a USB port or a card slot that mediates the connection between the certification medium 200 and the key / certificate issuing device 100.

  When the key issuing unit 130 receives a request for issuing a public key certificate from the message decryption device 400 or the key information conversion device 500, the key generation unit 110 includes a public key and a private key corresponding to the public key. Is generated. Next, the certificate generation unit 120 will be described.

  When the key generation unit 110 generates the public key and the private key, the certificate generation unit 120 generates the public key, the expiration date, the e-mail address of the owner of the public key, the name of the certificate authority or registration authority, the certificate authority or registration A public key certificate including the signature information of the station is generated.

  The storage unit 140 stores the private key generated by the key generation unit 110, the public key certificate generated by the certificate generation unit 120, and information for identifying the private key and the destination of the public key certificate. . The storage unit 140 is a storage medium such as a hard disk device.

  In the following, the public key certificate that has expired is the old public key certificate, and after the old public key certificate is issued, the public key certificate that is newly issued is the new public key certificate. Call it. A private key corresponding to the new public key certificate is referred to as a new private key, and a private key corresponding to the old public key certificate is referred to as an old secret key. Further, a public key certificate issued in response to a request from the key information conversion apparatus 500 is referred to as a conversion public key certificate, and a private key corresponding to the conversion public key certificate is referred to as a conversion private key.

  In the following description, the expiration date of the old public key certificate and the conversion public key certificate is set to be longer than that of the old public key certificate. Next, the key issuing unit 130 will be described.

  When the key issuing unit 130 receives a request to issue a public key certificate from the message decryption apparatus 400 (more specifically, the certification medium 200 is set in the interface unit 160), the key generating unit 110 To generate a public key certificate and a private key. The generated public key certificate and private key are written in the certification medium 200.

  Upon receiving a request for issuing a public key certificate from the key information conversion apparatus 500, the key issuing unit 130 receives the conversion public key certificate generated by the certificate generation unit 120 and the conversion generated by the key generation unit 110. The secret key is transmitted (output) to the key information conversion apparatus 500 via the communication unit 150.

  The key issuing unit 130 receives the public key certificate generated by the certificate generation unit 120 and the key generation unit if security can be ensured when a request for issuing the public key certificate is received from the message decryption apparatus 400. The secret key generated by 110 may be transmitted (output) to the message decryption apparatus 400 via the communication unit 150 and written to the certification medium 200 set in the message decryption apparatus 400.

  Further, as will be described later, the key information conversion device 500 has the same device or medium (for example, the message decryption device 400 or the certification medium 200) to which the new public key certificate and the old public key certificate are provided. The key issuing unit 130 determines whether the new public key certificate and the old public key certificate in the received request match the destination device or medium. And the result (identical or non-identical) is transmitted.

  As a specific determination method for the identity of the new public key certificate and the old public key certificate, any method may be used regardless of a known method. For example, there is information for identifying the provision destination of the public key included in the new public key certificate and the public key included in the old public key certificate managed by the storage unit 140 by the key / certificate issuing device 100. If they are the same, it is determined that the device or medium to be provided is the same.

  In the following description, in response to a request from the key information conversion apparatus 500, the key / certificate issuing apparatus 100 determines whether the public key of the new public key certificate and the public key of the old public key certificate have the same destination. Although the determination is performed, the key information conversion apparatus 500 may determine the identity between the new public key certificate and the old public key certificate. Next, the certification medium 200 will be described.

  The certification medium 200 is a physical tamper resistance such as an IC (Integrated Circuit) card or USB for storing a public key certificate issued by the key / certificate issuing device 100 and a private key corresponding to the public key certificate. It is composed of devices with characteristics. FIG. 3 is a block diagram showing a functional configuration of the certification medium 200.

  As shown in FIG. 3, the certification medium 200 includes an interface unit 210, a key acquisition unit 220, and a storage unit 230.

  The interface unit 210 uses the certification medium 200 as an interface such as a USB terminal or an IC card terminal for connecting to the key / certificate issuing device 100.

  The key acquisition unit 220 receives the private key and public key certificate output from the key / certificate issuing device 100 and stores them in the storage unit 230.

  The storage unit 230 is a storage medium such as a memory that stores the private key and public key certificate received by the key acquisition unit 220. The secret key is used only when performing the decryption process, and is normally information that cannot be referred to. The public key certificate is information that can be referred to from the message decryption device 400 in which the certification medium 200 is set.

  FIG. 4 is a diagram illustrating examples of public key certificates and private keys stored in the storage unit 230. As illustrated in FIG. 4, the storage unit 230 stores a secret key and a public key certificate in association with each other. In FIG. 4, a secret key and a public key certificate with different validity periods (a private key A and a public key certificate A with a long validity period, and a secret key B and a public key certificate B with a short validity period) are stored. An example. In the following description, the user stores a plurality of secret keys and public key certificates with different expiration dates in the certification medium 200 in the certification medium 200.

  Note that only one set of public key certificate and private key may be stored in the certification medium 200. For example, as illustrated in FIG. 9, the storage unit 230 may store a new public key certificate and a new public key, which will be described later, in association with each other.

  When the certification medium 200 is set in the message decryption apparatus 400 as indicated by a broken line A in FIG. 1, the message decryption apparatus 400 uses the secret key stored in the certification medium 200. Decryption processing is performed. Specific processing will be described later. Next, returning to FIG. 1, the message encryption device 300 will be described.

  The message encryption device 300 is an information processing device such as a PC (Personal Computer), and is a device that encrypts a message and transmits it to the message decryption device 400. The encryption target is not limited to the message, but may be data.

  FIG. 5 is a block diagram illustrating a functional configuration of the message encryption device 300. As illustrated in FIG. 5, the message encryption device 300 includes a storage unit 310, an encryption unit 320, a display unit 330, and a communication unit 340.

  The communication unit 340 includes a communication interface such as a network board, and controls communication between the message encryption device 300 and the message decryption device 400.

  The storage unit 310 is a storage medium such as a memory or an HDD (hard disk drive) that stores a message to be encrypted and a common key for encrypting the message to be encrypted. A message to be encrypted is input from an input device (not shown) such as a keyboard or a mouse.

  The encryption unit 320 acquires a public key certificate from the message decryption device 400 and a conversion public key certificate from the key information conversion device 500 in response to an instruction from the input device (not shown) described above. Then, the display unit 330 is caused to display the owner and expiration date of the acquired public key certificate and conversion public key certificate.

  In addition, the encryption unit 320 encrypts the message stored in the storage unit 310 using the common key. Further, the encryption unit 320 uses the public key certificate acquired from the message decryption apparatus 400 and the conversion public key certificate acquired from the key information conversion apparatus 500 to use a common key for each public key certificate. Is encrypted.

  Any method may be used as the encryption method. For example, it is conceivable to use a method such as S / MIME (Secure Multipurpose Internet Mail Extensions), PGP (Pretty Good Privacy), or the like.

  FIG. 6 is a diagram illustrating an example in which the encryption unit 320 encrypts the message stored in the storage unit 310.

  As shown in FIG. 6, the encryption unit 320 encrypts a message to be encrypted with a common key to generate an encrypted message. Then, the encryption unit 320 generates common key information including the common key and related information of the common key (creation date, creator, etc.), and encrypts the generated common key information with the public key certificate. . The encryption unit 320 according to the present embodiment performs encryption using both the public key certificate acquired from the message decryption device 400 and the conversion public key certificate. In addition, it does not restrict | limit to encrypting with two types of public key certificates, You may encrypt with three or more types of public key certificates.

  Further, the encryption unit 320 generates key information obtained by combining the common key information encrypted with the public key certificate and the public key certificate obtained by encrypting the common key information. In the present embodiment, the public key certificate acquired from the message decryption apparatus 400, the conversion public key certificate, and key information corresponding to each are generated. When a plurality of pieces of key information are generated in this way, the encryption unit 320 generates encryption key information that combines these types of key information, and an encryption that combines the encryption key information and the encrypted message. Generate a generalized object. Then, according to the instruction of the encryption unit 320, the communication unit 340 transmits the generated encrypted object to the message decryption device 400.

  In the example illustrated in FIG. 6, the encryption unit 320 encrypts the common key information as the key information 1 using the common key information and the public key certificate (public key certificate A) acquired from the message decryption device 400. The key information 1 is generated by combining the common key information encrypted with the public key certificate A and the public key certificate A. Further, the encryption unit 320 encrypts the common key information with the common key and the conversion public key certificate acquired from the key information conversion apparatus 500, and converts the common key information and the conversion with the conversion public key certificate. The key information 2 is generated by combining the public key certificate. Hereinafter, like the key information 2, key information obtained by combining the common key information encrypted with the conversion public key certificate and the conversion public key certificate is referred to as conversion key information.

  In the example shown in FIG. 6, only one public key certificate (public key certificate A) is acquired from the message decryption apparatus 400. However, as shown in FIG. When a plurality of public key certificates with different expiration dates are stored in the message decrypting device 400, a public key certificate (public key certificate B) different from the public key certificate A is stored. It may be used to encrypt the common key information. In that case, the encryption unit 320 adds the encryption key information as the key information N. Subsequently, returning to FIG. 5, the display unit 330 will be described.

  The display unit 330 is configured by a display such as an LCD (Liquid Crystal Display), and displays the owner and expiration date of the public key certificate and the conversion public key certificate acquired by the encryption unit 320. The user of the message encryption device 300 refers to the displayed information and determines a public key certificate for encrypting the common key information. Next, returning to FIG. 1, the message decoding device 400 will be described.

  The message decryption device 400 is configured from an information processing device such as a PC (Personal Computer), and is a device for decrypting an encrypted message.

  FIG. 7 is a block diagram showing a functional configuration of the message decryption apparatus 400. As illustrated in FIG. 7, the message decryption apparatus 400 includes a storage unit 410, a decryption unit 420, a key update unit 430, a display unit 440, a communication unit 450, an interface unit 460, and an encryption unit 470. And.

  The communication unit 450 includes a communication interface such as a network board, and controls communication with the message encryption device 300, the message decryption device 400, or the key information conversion device 500. Thereby, various information can be transmitted and received. For example, the communication unit 450 receives an encrypted object from the message encryption device 300. Other information to be transmitted and received will be described later.

  The interface unit 460 is an interface such as a USB terminal or an IC card terminal that mediates the connection between the message decryption apparatus 400 and the certification medium 200. When the certification medium 200 is set in the interface unit 460, it is possible to read the public key certificate or perform decryption using the private key corresponding to the public key certificate.

  The storage unit 410 is a storage medium such as an HDD (Hard Disk Drive) that stores the public key certificate read from the certification medium 200. In the following description, the storage unit 410 stores two types of public key certificates, a public key certificate A with a long validity period and a public key certificate B with a short validity period. These two types of public key certificates are disclosed on the communication network 600.

  In addition, the storage unit 410 stores an identification ID generated by the decryption unit 420 described later in association with key information included in the encrypted object received from the message encryption device 300.

  FIG. 8 is a diagram illustrating the concept of information stored in the storage unit 410. As illustrated in FIG. 8, the storage unit 410 stores a plurality of types of public key certificates, encrypted objects received from the message encryption device 300, and identification IDs in association with each other. In the storage unit 410, an identification ID is associated with each key information included in the encrypted object.

  The public key certificate stored in the storage unit 410 is not limited to two types. For example, as illustrated in FIG. 10, the storage unit 410 may further store a new public key certificate. Subsequently, returning to FIG. 7, the decoding unit 420 will be described.

  The decryption unit 420 takes out the public key certificate stored in the certification medium 200 and stores it in the storage unit 410 described above. Further, the decryption unit 420 acquires an encrypted object from the message encryption device 300 via the communication unit 450. Then, the decryption unit 420 generates an identification ID for identifying the key information included in the acquired encrypted object, for example, by generating a random number, and associates the generated identification ID with the key information to store the storage unit. 410 is stored.

  Further, when the decryption unit 420 acquires an encrypted object from the message encryption device 300 via the communication unit 450, the public key certificate included in the key information of the acquired encrypted object is the old public key certificate. It is determined whether it is a book.

  If the decryption unit 420 determines that the public key certificate is an old public key certificate, the decryption unit 420 causes the display unit 440 to display that the public key certificate has expired.

  Thus, when the decryption unit 420 displays on the display unit 440 that the validity period of the public key certificate has expired, the user of the message decryption device 400 makes a new disclosure to the key / certificate issuing device 100. A request for issuing a key certificate is made, and a new public key certificate and a new private key corresponding to the new public key certificate are stored in the certification medium 200.

  Thereafter, when the certification medium 200 is set in the interface unit 460, the decryption unit 420 reads the new public key certificate stored in the certification medium 200 and stores it in the storage unit 410 described above. Subsequent processing is performed by the key update unit 430.

  In addition, when the decryption unit 420 determines that the public key certificate is not an expired old public key certificate, the decryption unit 420 further determines that the public key certificate has an expiration date compared to other public key certificates. It is determined whether it is a short public key certificate.

  When the decryption unit 420 determines that the public key certificate included in the key information is not a public key certificate with a short validity period, the common key information is encrypted with a public key certificate with a long validity period. This is displayed on the display unit 440.

  When the decrypting unit 420 determines that the public key certificate included in the key information is a public key certificate with a short expiration date, the public key with a short expiration date stored in the certification medium 200 The common key information is decrypted with the private key corresponding to the certificate. Then, the encryption unit 470 encrypts the decrypted common key information with a public key certificate with a long validity period. Thereafter, the encryption unit 470 causes the display unit 440 to display that the common key information has been encrypted with a public key certificate with a long validity period. As a result, the expiration of the validity period due to the public key certificate having a short validity period can be suppressed.

  As described above, when the decryption unit 420 displays on the display unit 440 that the common key information is encrypted with a public key certificate with a long validity period, it corresponds to the public key certificate with a long validity period. The secret key to be extracted is taken out from the certification medium 200, the encrypted common key information is decrypted, and the encrypted message is decrypted with the decrypted common key information.

  Further, as will be described later, when the key updating unit 430 displays that the new key information (described later) is added to the encryption object on the display unit 440, the decrypting unit 420 is included in the new key information (described later). The encrypted common key information is decrypted with the new secret key corresponding to the new public key certificate, and the encrypted message is decrypted with the decrypted common key information.

  By the way, when the decryption unit 420 determines that the public key certificate included in the encrypted object is an old public key certificate whose validity period has expired, the old public key certificate is used even if the certification medium 200 is used. Decryption with the private key corresponding to the certificate is not permitted. In this case, the encrypted message cannot be read. Therefore, in this embodiment, the public key certificate for encrypting the common key information is changed from the old public key certificate whose valid period has expired to the public key certificate within the valid period in the key information conversion apparatus 500. Resolve by requesting conversion.

  That is, when the decryption unit 420 determines that the public key certificate is the old public key certificate, the key update unit 430 controls the communication unit 450, and the communication unit 450 corresponds to the conversion key information. The identification ID, new public key certificate, old public key certificate, and conversion key information are transmitted to the key information conversion apparatus 500. As a result, the communication unit 450 of the message decryption apparatus 400 receives, from the key information conversion apparatus 500, key information obtained by encrypting the common key information with the new public key certificate (hereinafter referred to as new key information). Therefore, since the message decryption apparatus 400 can decrypt the common key information from the new key information with the private key corresponding to the new public key certificate, the message can be decrypted.

  The new key information is obtained by decrypting the common key information encrypted with the conversion public key certificate with the conversion private key by the key information conversion apparatus 500 and converting the decrypted common key information with the new public key certificate. After encryption, the common key information encrypted with the new public key certificate and the new public key certificate are combined.

  That is, in the present embodiment, when the private key corresponding to the old public key certificate whose valid period has passed becomes unavailable, the message decryption apparatus 400 uses the old public key certificate whose valid period has passed. The key information conversion apparatus 500 is requested to convert the key to a new public key certificate whose validity period has not expired. When the key information conversion apparatus 500 receives the request, the key information conversion apparatus 500 determines that the identity of the providing destination of the old public key certificate and the new public key certificate whose validity period has not expired is guaranteed. In addition, the key information is converted, and the message decrypting apparatus 400 is provided with the new key information based on the new public key certificate. As a result, while maintaining security, it is possible to convert an old public key certificate whose expiration date has passed into new key information using a new public key certificate within the expiration date. Such conversion of the key information is possible because conversion key information that can be decrypted only by the key information conversion apparatus 500 is added to the encryption object.

  After the transmission, the key update unit 430 indicates from the key information conversion device 500 via the communication unit 450 that the new public key certificate and the old public key certificate are not the same destination (error notification). When received, the fact is displayed on the display unit 440. As a result, key conversion by another device can be suppressed, so that safety can be improved.

  When the key update unit 430 receives the identification ID corresponding to the new key information, the new public key certificate, and the conversion key information from the key information conversion apparatus 500, the key update unit 430 includes the key information included in the encryption object. Then, the key information having the same identification ID as the conversion identification ID is searched, and the new key information is added after the searched conversion identification ID. Then, the key update unit 430 causes the display unit 440 to display that the new key information has been added to the encryption object. Next, the display unit 440 will be described.

  The display unit 440 includes a display such as an LCD (Liquid Crystal Display) and displays various information. Examples of information to be displayed include the fact that the public key certificate has expired, the common key information is encrypted with a public key certificate with a long validity period, or the old public key certificate For example, the destination of the new public key certificate is not the same. Further, the display unit 440 displays that the new key information has been added to the encryption object when the key update unit 430 has added the new key information to the encryption object.

  Returning to FIG. 1, when the validity period of the public key certificate stored in the message decryption apparatus 400 has expired, the key information conversion apparatus 500 uses the conversion key information and the new public key certificate within the validity period. New key information is generated, and the generated new key information is provided to the message decryption apparatus 400.

  FIG. 11 is a block diagram illustrating a functional configuration of the key information conversion apparatus 500. As shown in FIG. 11, the key information conversion apparatus 500 includes an acquisition unit 510, a key storage unit 520, a decryption unit 530, an encryption unit 540, a hash calculation unit 560, a signature generation unit 565, and an output unit. 570, determination unit 580, registration unit 590, and communication unit 550 are included.

  The communication unit 550 includes a communication interface such as a network board, and mediates communication between the key / certificate issuing device 100 and the message decryption device 400.

  The key storage unit 520 stores the conversion public key certificate and the conversion private key in association with each other. The key storage unit 520 is a storage medium such as an HDD (Hard Disk Drive). FIG. 12 is a diagram illustrating a state in which the key storage unit 520 stores the conversion public key and the conversion secret key in association with each other. It is assumed that the conversion public key and the conversion private key are provided from the key / certificate issuing device 100.

  Returning to FIG. 11, the acquisition unit 510 issues a conversion public certificate issuance request to the key / certificate issuing device 100 via the communication unit 550, and the key / certificate issuing device 100 sends a conversion request. Obtain public key certificate and conversion private key. In other words, the acquisition unit 510 has a function as a key acquisition unit.

  The registration unit 590 registers the acquired conversion public key certificate and conversion private key in the key storage unit 520. The registered conversion public key certificate is provided to the message encryption device 300 or the like. Thereby, the acquisition unit 510 can acquire the conversion key information encrypted with the conversion public key certificate from the message decryption apparatus 400.

  The output unit 570 transmits (outputs) the conversion public key certificate to the message encryption device 300 via the communication unit 550. In other words, the output unit 570 has a function as a key output unit.

  Further, the acquisition unit 510 includes an old public key certificate that has expired as a public key of the message decryption apparatus 400, conversion key information including a common key encrypted with the conversion key certificate, The identification ID corresponding to the key information and the new public key certificate within the validity period as the public key of the message decryption apparatus 400 are acquired from the message decryption apparatus 400. In other words, the acquisition unit 510 has a function as an acquisition unit.

  When the determination unit 580 obtains the conversion key information, the identification ID corresponding to the conversion key information, the new public key certificate, and the old public key certificate from the message decryption device 400, the key / certificate Whether the new public key certificate and the old public key certificate are transmitted to the issuing apparatus 100 via the communication unit 550, and the owners of the new public key certificate and the old public key certificate are the same. Request to make a determination.

  When the determination unit 580 receives a notification from the key / certificate issuing device 100 as to whether the new public key certificate and the old public key certificate are provided to the same destination, the determination unit 580 determines the content. To do.

  If the determination unit 580 determines that the provision destination of the new public key certificate and the old public key certificate is not the same, the determination unit 580 causes the message decryption device 400 to store the new public key certificate and the old public key certificate. An error notification indicating that the destination is not the same is transmitted via the communication unit 550.

  When the determination unit 580 determines that the provision destination of the new public key certificate and the old public key certificate is the same, the decryption unit 530 stores the obtained conversion key information in the key storage unit 520. Decrypt with the stored private key corresponding to the public key certificate for conversion to obtain common key information. The acquired common key information is output to the encryption unit 540 together with the new public key certificate.

  When the common key information and the new public key certificate are input from the decryption unit 530, the encryption unit 540 encrypts the common key information with the new public key certificate. Furthermore, the encryption unit 540 combines the encrypted common key information and the new public key certificate whose expiration date has been updated to generate new key information based on the new public key certificate. Then, the generated new key information is output to output section 570. Further, the encryption unit 540 outputs the generated new key information to the hash calculation unit 560.

  The hash calculation unit 560 calculates a hash value of the new key information generated by the encryption unit 540.

  The signature generation unit 565 encrypts the calculated hash value with a public key for electronic signature, and generates signature information for authenticating that the information is from the key information conversion apparatus 500. The generated signature information is output to the output unit 570. It should be noted that the authentication process using the electronic signature performed by the message decryption apparatus 400 is omitted because it is possible to use any technique regardless of a known technique.

  Upon receiving the generated signature information, the output unit 570 decrypts the generated new key information, the new public key certificate, and the identification ID corresponding to the conversion key information in addition to the received signature information. Output to the composing apparatus 400 via the communication unit 550. By adding the signature information and outputting the message to the message decryption apparatus 400, the message decryption apparatus 400 decrypts the signature information using the conversion public key certificate, thereby transmitting the new information transmitted from the key information conversion apparatus 500. It can be guaranteed that it is key information. Thereby, security can be improved.

  FIG. 13 illustrates a message between the message decryption apparatus 400 and the key information conversion apparatus 500 when it is determined that the validity period of the public key certificate is not valid when the message decryption apparatus 400 performs decryption. It is a figure which shows the outline in the case of delivering the various data mentioned above.

  As illustrated in FIG. 13, when it is determined that the validity period of the public key certificate is not valid, the message decryption apparatus 400 (identification ID 2 corresponding to the key information 2 in the example illustrated in FIG. 10). A new public key certificate, an old public key certificate (public key certificate B in the example shown in FIG. 10), and conversion key information (key information 2 in the example shown in FIG. 10). The data is transmitted to the conversion device 500.

  In the key information conversion apparatus 500, the determination unit 580 requests the key / certificate issuing apparatus 100 to determine whether the new public key certificate and the old public key certificate are provided to the same destination. When it is determined that the new public key certificate and the old public key certificate have the same destination, the decryption unit 530 converts the conversion private key corresponding to the conversion public key certificate of the key information 2. To decrypt common key information. Then, the encryption unit 540 encrypts the extracted common key information with the new public key certificate. Furthermore, the encryption unit 540 combines the encrypted common key information and the new public key certificate to generate new key information.

  Thereafter, the output unit 570 transmits (outputs) the generated new key information to the message decryption apparatus 400 together with the signature information and the identification ID via the communication unit 550. In other words, the output unit 570 has a function as output means.

  Then, the key update unit 430 of the message decryption apparatus 400 adds the new key information received from the key information conversion apparatus 500 to the encrypted object using the identification ID as a key. As a result, new key information based on the new public key certificate within the valid period is added to the encrypted object. Therefore, the encrypted object can be decrypted by using the secret key corresponding to the new public key certificate.

  Next, an execution process performed in the information processing system 1000 described above will be described.

  FIGS. 14A and 14B are sequence diagrams illustrating a processing procedure from when the private key and the public key certificate are issued to when the key information including the public key certificate expired is updated. is there.

  As shown in the figure, the certification medium 200 receives a public key certificate and a private key corresponding to the public key certificate from the key / certificate issuing device 100 by the user's operation, and makes it public. The key certificate and the private key are written (step S801). Then, when the certification medium 200 is set, the message decryption apparatus 400 reads the public key certificate from the certification medium 200 (step S802). Then, the decryption unit 420 stores the read public key certificate in the storage unit 410 (step S803).

  On the other hand, the output unit 570 of the key information conversion apparatus 500 transmits the conversion public key certificate to the message encryption apparatus 300 via the communication unit 550 (step S804). It is assumed that the conversion public key certificate has been issued from the key / certificate issuing device 100 in advance.

  Then, the communication unit 450 of the message decryption apparatus 400 transmits the stored public key certificate to the message encryption apparatus 300 and the like together with the fact that the public key certificate is encrypted (step S805).

  Thereafter, the encryption unit 320 of the message encryption device 300 encrypts the message stored in the storage unit 310 using the common key, and obtains the public key certificate obtained from the message decryption device 400 and the key information conversion device. Using each of the conversion public key certificates acquired from 500, the common key is encrypted to generate an encrypted object (step S806).

  Thereafter, the communication unit 450 of the message decryption apparatus 400 receives the encrypted object from the message encryption apparatus 300 (step S807). Then, the decryption unit 420 determines whether or not the public key certificate of the key information included in the received encrypted object is an old public key certificate whose valid period has passed (step S808).

  Then, when the decryption unit 420 determines that the public key certificate is an old public key certificate whose valid period has passed (step S808; Yes), it indicates that the public key certificate has expired. It is displayed on the display unit 440 (step S809). The subsequent processing will be described with reference to FIG.

  On the other hand, when it is determined that the public key certificate is not the old public key certificate (step S808; No), the decryption unit 420 further determines whether the public key certificate is a public key certificate with a short expiration date. Is determined (step S810).

  If the decryption unit 420 determines that the public key certificate is not a public key certificate with a short validity period (step S810; No), the common key information is encrypted with the public key certificate with a long validity period. Is displayed on the display unit 440 (step S811).

  On the other hand, when the decryption unit 420 determines that the public key certificate is a public key certificate with a short validity period (step S810; Yes), the key update unit 430 supports a public key certificate with a short validity period. The public key certificate is decrypted with the private key to be extracted, the common key information is extracted, and the extracted common key information is encrypted with the public key certificate with a long expiration date and stored (step S812). After that, the key update unit 430 displays on the display unit 440 that the encrypted object has been encrypted with the private key corresponding to the public key certificate with a long validity period (step S813).

  Next, the process after step S809 will be described with reference to FIG. First, by the user's operation, the certification medium 200 receives a new public key certificate with a new validity period and a new private key corresponding to the new public key certificate from the key / certificate issuing device 100. Is issued, a new public key certificate and a new secret key are written (step S814). Then, when the certification medium 200 is set, the message decryption apparatus 400 reads the new public key certificate from the certification medium 200 (step S815). Then, the decryption unit 420 extracts the new public key certificate stored in the certification medium 200 and stores it in the storage unit 410 (step S816).

  After that, the key update unit 430 controls the communication unit 450, and the communication unit 450 converts the conversion key information, the identification ID stored in association with the conversion key information, the new public key certificate, The public key certificate is transmitted to the key information conversion apparatus 500 (step S817).

  Then, the acquisition unit 510 of the key information conversion device 500 receives, from the message decryption device 400 via the communication unit 550, conversion key information, an identification ID stored in association with the conversion key information, After acquiring the new public key certificate and the old public key certificate, the determination unit 580 transmits the new public key certificate and the old public key certificate to the key / certificate issuing apparatus 100 ( Step S818).

  Next, when the key / certificate issuing device 100 receives the new public key certificate and the old public key certificate, the provision destination of the new public key certificate and the old public key certificate is the same. It is determined whether or not there is (step S819). Then, the key / certificate issuing apparatus 100 transmits the determination result to the key information conversion apparatus 500 (step S820).

  Thereafter, the determination unit 580 of the key information conversion device 500 determines whether or not the key / certificate issuing device 100 has received a result indicating that the new public key certificate and the old public key certificate are provided to the same destination. Determination is made (step S821).

  If the determination unit 580 determines that the provision destinations of the new public key certificate and the old public key certificate are not the same (step S821; No), the message decrypting apparatus 400 sends the new public key certificate and the old public key certificate. An error notification indicating that the public key certificate is not the same destination is transmitted (step S822). The message decryption apparatus 400 displays an error to that effect and ends the process (step S823).

  On the other hand, when the determination unit 580 determines that the new public key certificate and the old public key certificate are provided to the same destination (step S821; Yes), the decryption unit 530 receives the message from the message decryption device 400. The conversion key information is decrypted with the conversion private key corresponding to the conversion public key certificate to obtain the common key information (step S824). The acquired common key information is output to the encryption unit 540.

  Thereafter, the encryption unit 540 encrypts the common key information with the new public key certificate (step S825). Further, the encryption unit 540 combines the encrypted common key information and the new public key certificate to generate new key information (step S826).

  Next, the hash calculation unit 560 calculates a hash value of the new key information (step S827). After that, the signature generation unit 565 encrypts the calculated hash value with a public key for signature information, and generates signature information (step S828).

  Then, the output unit 570 outputs (transmits) the generated new key information, the new public key certificate, and the identification ID to the message decryption apparatus 400 via the communication unit 550 in addition to the generated signature information. (Step S829).

  Then, the key update unit 430 of the message decryption apparatus 400 performs an authentication process using the received signature information, and confirms that the new key information is transmitted from the key information conversion apparatus 500 (step S830). When it cannot be confirmed that the new key information is transmitted from the key information conversion apparatus 500, the fact that the update has failed is displayed on the display unit 440, and the process is terminated.

  On the other hand, if the key update unit 430 can confirm that the new key information is transmitted from the key information conversion apparatus 500, the key update unit 430 searches for key information having the same identification ID as the identification ID received from the key information conversion apparatus 500. The new key information is added after the searched key information (step S831). Thereafter, the key update unit 430 displays on the display unit 440 that the new key information has been added to the encryption object (step S832). When the process of step S832 ends, all the processes in the present embodiment end.

  As described above, when the key information converting apparatus 500 includes the old key information whose valid period has passed in the encrypted object included in the message decrypting apparatus 400, the new key information encrypted with the new public key certificate. Can be provided to the message decryption apparatus 400.

  That is, in this embodiment, the common key information is decrypted with the conversion public key certificate and the private key corresponding to the conversion public key certificate, and the decrypted common key information is converted into a new public key certificate. The encryption processing is characterized in that it is performed by the key information conversion apparatus 500 arranged on the network that cannot be directly operated.

  For example, the conversion public key certificate and the private key corresponding to the conversion public key certificate can be stored in the message decryption apparatus 400 and key information can be converted, but the message can be directly operated. If the secret key is stored in the decryption device 400, it may be misused by a malicious third party. Therefore, in this embodiment, the key information conversion device 500 is arranged on the above-described network, and only when the old public key certificate and the new public key certificate providing device are the same, the conversion public key The common key information is extracted with the private key corresponding to the certificate, key information based on a new public key certificate is generated for the common key information, and is output to the message decryption apparatus 400. As a result, misuse by a malicious third party can be prevented, and the message can be decrypted by converting the key information when the validity period expires.

  In the key information conversion apparatus 500 according to the present embodiment, the hash calculation unit 560 calculates a hash value of the new key information, and the signature generation unit 565 generates signature information from the hash value. After that, since the signature information is transmitted together with the new key information to the message decryption apparatus 400, the message decryption apparatus 400 provided with the new key information can determine that the key information is not generated illegally.

  In the embodiment described above, the message decryption apparatus 400 transmits key information to the key information conversion apparatus 500, and the key information conversion apparatus 500 generates new key information and sends it to the message decryption apparatus 400. I decided to send it. However, as a modification, the above-described processes can be performed as one information processing apparatus 800 including the functions of the message decryption apparatus 400 and the key information conversion apparatus 500.

  FIG. 15 is a diagram illustrating an example of a case where the same processing as the above-described processing is performed inside the above-described information processing device 800 (for example, a message decoding device). As shown in FIG. 15, the key update unit 430 of the message decryption device 400 converts the public key certificate for conversion of the conversion key information (key information 2) included in the encrypted object received from the message encryption device 300. It is also possible to extract the common key information by decrypting the certificate with the conversion private key, and then encrypt the extracted common key information with the new public key certificate to generate new key information.

  Also, when the key update unit 430 determines the expiration date of the public key certificate included in the encrypted object received from the message encryption device 300 and is encrypted with a public key certificate with a shorter expiration date. The public key certificate with a short expiration date is decrypted with the private key corresponding to the public key certificate to extract the common key information, and the extracted common key information is encrypted with the public key certificate with a long expiration date. It is also possible to generate new key information.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1000 Information Processing System 800 Information Processing Device 100 Key / Certificate Issuance Device 110 Key Generation Unit 120 Certificate Generation Unit 130 Key Issued Unit 140 Storage Unit (Key / Certificate Issuance Device)
150 Communication unit (key / certificate issuing device)
160 Interface part (key / certificate issuing device)
200 Certification medium 210 Interface section (certification medium)
220 Key acquisition section 230 Storage section (certification medium)
300 Message Encryption Device 310 Storage Unit (Message Encryption Device)
320 encryption unit 330 display unit (message encryption device)
340 communication unit (message encryption device)
400 Message Decoding Device 410 Storage Unit (Message Decoding Device)
420 Decryption Unit 430 Key Update Unit 440 Display Unit (Message Decryption Device)
450 Communication unit (message decoding device)
460 interface unit (message decoding device)
470 Encryption unit (message decryption device)
500 Key Information Conversion Device 510 Acquisition Unit 520 Key Storage Unit 530 Decryption Unit (Key Information Conversion Device)
540 encryption unit (key information conversion device)
550 communication unit (key information conversion device)
560 hash calculation unit 565 signature generation unit 570 output unit 580 determination unit 590 registration unit 600 communication network

JP 2000-134195 A

Claims (9)

In an information processing device connected via a communication network to a decryption device that decrypts a message encrypted with a common key,
Key storage means for storing a first public key and a secret key corresponding to the first public key in association with each other;
Obtaining means for obtaining key information including a common key encrypted with the first public key, and a second public key within the validity period as a public key of the decryption device;
Decryption means for decrypting the common key contained in the acquired key information with a secret key stored in the key storage means and corresponding to the first public key;
An encryption means for encrypting the decrypted common key with the second public key and generating new key information with the second public key within an expiration date;
Output means for outputting the new key information generated by the encryption means to the decryption device;
An information processing apparatus comprising: Determination means for determining whether or not the second public key and the third public key expired as the public key of the decryption device are provided to the same device Further,
The acquisition means further acquires the third public key whose expiration date has expired from the decryption device,
The decryption means determines the common key when the determination means determines that the second public key and the third public key are provided to the same device. Decrypting,
The information processing apparatus according to claim 1. Connected to an issuing device for issuing the first public key via the communication network;
Key obtaining means for obtaining the first public key and a secret key corresponding to the first public key from the issuing device;
The key storage means is a registration means for registering the first public key acquired by the key acquisition means and a secret key corresponding to the first public key in the key storage means,
A key output unit that outputs the first public key to an encryption device that encrypts information using the first public key;
The acquisition means acquires key information including a common key encrypted with the first public key output by the key output means;
The information processing apparatus according to claim 1, wherein: A calculation unit that calculates a hash value of the new key information generated by the encryption unit;
The encryption means encrypts the hash value with the secret key corresponding to the first public key, and generates signature information that can be authenticated with the first public key.
The output means further outputs the generated signature information together with the new key information to the decryption device;
The information processing apparatus according to any one of claims 1 to 3. An information processing method executed by an information processing apparatus connected via a communication network to a decryption apparatus that decrypts a message encrypted with a common key,
The information processing apparatus includes key storage means for storing a first public key and a secret key corresponding to the first public key in association with each other,
An obtaining step in which an obtaining unit obtains key information including a common key encrypted with the first public key, and a second public key within an expiration date as a public key of the decryption device;
A decrypting step for decrypting the common key included in the acquired key information with a secret key corresponding to the first public key stored in the key storage unit;
An encryption step for encrypting the decrypted common key with the second public key, and generating new key information with the second public key within an expiration date;
An output means for outputting the new key information generated in the encryption step to the decryption device; and
An information processing method characterized by comprising: An information processing system in which an encryption processing device that encrypts a message, a decryption processing device that decrypts the encrypted message, and an information processing device are connected via a communication network,
The encryption processing device includes:
The message is encrypted using the common key, the common key is encrypted using the first public key provided from the information processing apparatus, and the common key is used using the third public key provided from the decryption apparatus. Encryption means for encrypting,
The encrypted message, conversion key information including the common key encrypted with the first public key, key information including the common key encrypted with the third public key, Communication means for transmitting to the decryption processing device,
The decoding device
The encrypted message, the conversion key information, and the key information encrypted with the third public key are received, and an effective period in which the third public key can be decrypted has elapsed. A second public key within a valid period that can be decrypted and the key information for conversion are transmitted to the information processing apparatus and encrypted by the second public key from the information processing apparatus. Communication means for receiving new key information including the common key;
Decryption means for decrypting the new key information received from the information processing apparatus with a secret key corresponding to the second public key to obtain the common key, and decrypting the message with the common key; With
The information processing apparatus includes:
Key storage means for storing the first public key and a secret key corresponding to the first public key in association with each other;
Obtaining means for obtaining the conversion key information and the second public key within the valid period of decryption from a decryption processing device;
Decryption means for decrypting the common key included in the obtained conversion key information with a secret key stored in the key storage means and corresponding to the first public key;
Encryption means for encrypting the decrypted common key with the second public key, and generating new key information with the second public key within an expiration date;
Output means for outputting the new key information generated by the encryption means to the decryption device,
An information processing system characterized by this. The communication means of the decryption device further transmits the third public key whose expiration date has expired to the information processing device,
The information processing apparatus includes:
Determination means for determining whether or not the second public key and the third public key are provided to the same device; and
The acquisition means further acquires the third public key from the decryption device,
The decryption means determines the common key when the determination means determines that the second public key and the third public key are provided to the same device. Decrypting,
The information processing system according to claim 6. The information processing system further connects an issuing device via the communication network,
The issuing device is:
The first public key and a secret key corresponding to the first public key are issued to the information processing apparatus, and the second public key and the second public key are issued to the decryption apparatus. A secret key corresponding to the key, and an issuing means for issuing the third public key and the secret key corresponding to the third public key,
The information processing system according to claim 7. The determination unit of the information processing device outputs the second public key and the third public key to the issuing device, and from the determination result input from the issuing device, for the same device Determine if it was provided,
When the second public key and the third public key are input, the issuing device issues a device that is an issue destination of the second public key and the third public key. Determining whether or not they are the same, and outputting a determination result to the information processing device;
The information processing system according to claim 8.

Images