Nippon Telegraph and Telephone Corporation

Tomohide Yamamoto

Tetsutaro Kobayashi

Reo Yoshida

Hitoshi Fuji

Yuto Kawahara

Go Yamamoto

Kazuki Yoneyama

Hironobu Okuyama

To provide a terminal device that can share a session key for use in encryption communication with multiple terminal devices at a certain timing without relying on an existing server device. The terminal device includes: a list/request sending unit that, when the terminal device operates as an owner device, generates a key distribution request, signs the key distribution request, and transmits the key distribution request to a key distribution management device; a participation request sending unit that, when the terminal device operates as a general device, generates a participation request, signs the participation request, and transmits the participation request to the key distribution management device; a session key generating unit that executes an authentication-based multipoint key distribution algorithm of server-client type in cooperation with another terminal device participating in the session and with the key distribution management device to generate a session key; and a post-confirmation unit that, when the session key has been normally generated, transmits a success notice to the key distribution management device and receives a collective notice from the key distribution management device.

Terminal device, key distribution management device, server-client system, communication method, and programs

An encrypted communication is correctly decrypted even when key exchange completion notification is delayed. A key storage () stores at least one common key which is shared with another encrypted communication device. A key selecting unit () selects an encryption key from the at least one common key stored in the key storage (). An encrypting unit () generates encrypted data by encrypting, by using the encryption key, data to be transmitted to the other encrypted communication device. A transmitting unit () transmits, to the other encrypted communication device, the encrypted data with a key index, by which the encryption key is uniquely identified, added thereto. A receiving unit () receives the encrypted data with the key index added thereto from the other encrypted communication device. A key obtaining unit () obtains, from the at least one common key stored in the key storage (), a decryption key corresponding to the key index added to the encrypted data. A decrypting unit () decrypts the encrypted data by using the decryption key.

Encrypted communication device, encrypted communication system, encrypted communication method, and program

A server sends a key update request for requesting updating of the key, to a client terminal. The client terminal sends, to a key delivery server, a key delivery request for requesting the delivery of a key to the client terminal. The key delivery server delivers a key to the client terminal. The client terminal sends, to the server, a key reception notice indicating that the delivered key was received. The server sends, to the client terminal, a key-use start notice indicating that the client terminal starts data transmission and reception by using the delivered key with a different client terminal from the aforementioned client terminal. The client terminal performs data transmission and reception with the different client terminal by using the delivered key.

Data transmission and reception method and system

Plurality of users share a common key while permitting dynamic member change and computational complexity required for key exchange is reduced. The first key generation unitof the communication devices Ucomputes Rand c, or cbased on a twisted pseudo-random function. A session ID generation unitof a key distribution device S generates sid based on a target-collision resistant hash function and transmits sid to the communication devices U. A second key generation unitof the communication devices Ucomputes Tbased on a pseudo-random function. A third key generation unitof the key distribution device S computes k' and T&#x2032;based on the twisted pseudo-random function. A session key generation unitof the communication devices Ugenerates the common key Kbased on a pseudo-random function.

Key exchange method, key exchange system, communication device and storage medium therefore

Plurality of users share a common key while permitting dynamic member change and computational complexity required for key exchange is reduced. The first key generation unit computes Rand cbased on a twisted pseudo-random function. A session ID generation unit generates sid based on a target-collision resistant hash function and transmits (sid, R, R) to communication devices U. A second key generation unit of a representative communication device Ucomputes Tbased on a pseudo-random function. A second key generation unit of general communication devices Ucomputes Tbased on the pseudo-random function. A third key generation unit computes k' based on the twisted pseudo-random function and computes T&#x2032;with respect to each j. A session key generation unit of the general communication devices Ucomputes Kand k. The session key generation unit generates a common key Kbased on the pseudo-random function.

Key exchange method, key exchange system, key distribution device, communication device, and program

At the time of setting authority, a management apparatus stores a database in which authority information corresponding to authority to physically drive a drive apparatus, which is a tangible object, using a terminal apparatus, and registration identification information corresponding to a subject that is given the authority are associated, and outputs information representing any of the registration identification information; and a permission apparatus receives and stores the information. At the time of exercising the authority, the terminal apparatus outputs information representing identification information, and the permission apparatus receives the information and, when the identification information corresponds to registration identification information comprised in setting information, outputs information representing authority exercise information required to exercise the authority. The terminal apparatus receives the information representing the authority exercise information and outputs a drive signal corresponding to the authority exercise information. By this drive signal, a drive apparatus, which is a tangible object, is physically driven.

Security system, management apparatus, permission apparatus, terminal apparatus, security method and program

Name information which is generated by using a value corresponding to a decryption key and address information of a key cloud device which provides a cloud-key management type decryption service in which the decryption key is used are stored in a storage of a directory service device in a manner to associate the name information with the address information, and a searching unit of the directory service device searches the storage by using the inputted name information to obtain address information corresponding to the inputted name information.

Directory service device, client device, key cloud system, method thereof, and program

A private key is held which conforms to an ElGamal encryption system on a semigroup, calculation of an order of an element of the semigroup being computationally difficult, information corresponding to ciphertext conforming to the ElGamal encryption system is input, a private key s is used to decrypt the information corresponding to the ciphertext in conformance to the ElGamal encryption system, and information corresponding to a result of decrypting the ciphertext is obtained and output. Alternatively, whether it is computationally difficult or easy to calculate the order of the element of the semigroup is determined, and the safety of a decryption service providing device is evaluated based on the determination result.

Growing community of inventors

Musashino, Japan

Tomohide Yamamoto