Nippon Telegraph and Telephone Corporation

Yuki Okano

Tetsutaro Kobayashi

Reo Yoshida

Ryo Nishimaki

Koha Kinjo

Tetsuya Okuda

Yuto Kawahara

Tsunekazu Saito

Masahiro Matsui

A signature verification system includes a signature generation server, a signature verification server, and a verification key management server that are connected to one another via a communication network. The signature generation server includes: reporting means for, when a signing key and a verification key are generated by a publisher, reporting the verification key and publisher identification information that identifies the publisher to the verification key management server; and signature generation means for signing a bid request issued by the publisher with use of the signing key. The verification key management server includes: registration means for registering the publisher identification information and the verification key that were reported by the reporting means in a storage unit in association with information that enables specifying a version of the verification key.

Signature verification system, verification key management apparatus, verification key management method and program

A server device includes a memory and a processor to execute saving an encrypted text of a message generated by encrypting the message with a message key generated from a shared key and a group identifier, by using a message key identifier as an identifier of the message key as a key; saving an encrypted text of the message key generated by encrypting the message key to be re-encryptable by using the shared key, by using the message key identifier as a key; and receiving, after update of the shared key, a re-encryption key from a communication terminal that has generated the re-encryption key by using the shared key and the updated shared key, using the re-encryption key to generate a re-encrypted encrypted text of the message key, and overwriting the encrypted text of the message key before re-encryption with the re-encrypted encrypted text of the message key.

Server device, communication terminal, communication system, and program

A communication system includes a transmitting device configured to transmit information, and a receiving device configured to receive the information, the receiving device includes a determination unit configured to determine whether or not an electronic certificate of the transmitting device used for a communication with the transmitting device is an EV certificate, and a process that is performed is varied according to a determination result of the determination unit.

Communication system, communication apparatus, communication method, program and advertisement communication system

The present invention makes it possible to improve confidentiality. A communication terminal stores a session key shared with other communication terminals (S). The communication terminal makes a pair of an index generated by using the session key for a character string relating to a message and a message identifier, and transmits it to a server apparatus (S). The server apparatus stores the pair of the index and the message identifier (S). The communication terminal generates, when the session key is updated, a re-encryption key with a session key before update and a session key after update (S). The server apparatus updates, by using the re-encryption key, the stored index to an index generated by using the session key after update (S). The communication terminal encrypts a search keyword with the session key to generate a search query (S). The server apparatus extracts a message identifier of which the index matches the search query (S).

Message transmission system, communication terminal, server apparatus, message transmission method, and program

A key exchange device is provided that includes: a shared secret key storage in which shared secret information mkwhich is information different from a secret key of the key exchange device is stored; an authentication information addition unit that generates authentication information &#x3c3;, by which authentication is performed and falsification is detected, for key exchange information e, which is output to the outside, by using the shared secret information mk; and an authentication information verification unit that receives key exchange information eand authentication information &#x3c3;corresponding to the key exchange information efrom the outside, verifies the authentication information &#x3c3;using the shared secret information mk, and, if the authentication information &#x3c3;is not successfully verified, stops a key exchange, and the shared secret information mkis a value that is used in a generation process in a key exchange.

Key exchange device, key exchange system, key exchange method, and key exchange program for exchanging a key with another device

With respect to a key distribution system including N terminal devices Uand a key distribution server used for exchanging a session key, the key distribution system includes an isogeny calculating unit configured to calculate a first public value using a basis of a first torsion subgroup of a predetermined elliptic curve at an odd-numbered terminal device Uand calculate a second public value using a basis of a second torsion subgroup of the predetermined elliptic curve at an even-numbered terminal device U, when N is an even number, a distributing unit configured to distribute the first public value calculated at the odd-numbered terminal device Uto a terminal device Uand a terminal device U, and distribute the second public value calculated at the even-numbered terminal device Uto a terminal device Uand a terminal device U, from the key distribution server, a key generating unit configured to use second public values distributed by the distributing unit to generate the session key at the odd-numbered terminal device U, and use first public values distributed by the distributing unit to generate the session key at the even-numbered terminal device U, wherein the isogeny calculating unit calculates the first public value using the basis of the first torsion subgroup and the second public value using the basis of the second torsion subgroup at a predetermined terminal device Uamong the terminal devices U, when N is an odd number.

Key distribution system, terminal device, key distribution method, and program

A communication terminal which is capable of reducing load of a server apparatus by reutilizing a message key to be used for encrypting a message is provided. The communication terminal includes a session key storage part which stores a session key which is shared with another communication terminal and which is not shared with the server apparatus, a message key generating part which generates a message key, a message key storage part which stores the message key to be reutilized in association with a message key identifier, a message encrypting part which generates a message encrypted text based on a common key cryptosystem using the message and the message key, a message key encrypting part which generates a message key encrypted text based on a common key cryptosystem which can perform re-encryption using the session key and the message key, and an encrypted text transmitting part which transmits a group identifier which is an identifier of a group to which an own terminal belongs, the message key encrypted text or the message key identifier, and the message encrypted text to the server apparatus.

Communication terminal, server apparatus, and program

In Round1, each terminal device transmits a key encryption key which conforms to post-quantum cryptography to a neighboring terminal device; in Round2, each terminal device generates a key capsule of a key-shared-between-two-parties using the received key encryption key and returns the key capsule to a terminal device which is a source of the key encryption key; in Round3, each terminal device generates information based on the key-shared-between-two-parties and transmits the information to a key distribution management device and the key distribution management device distributes information, which is obtained based on these pieces of information, to the terminal devices. Each terminal device calculates a shared key based on the distributed information.

Quantum-proof multiparty key exchange system, quantum-proof multiparty terminal device, quantum-proof multiparty key exchange method, program, and recording medium

There is provided an encrypted message search technique making it difficult to, at the time of searching for a message in a state of being encrypted, guess content of the search and a result of the search. There are included: an encrypted search secret key transmission step of a terminal generating an encrypted search secret key from a search secret key generated each time an update interval set in advance elapses and transmitting the encrypted search secret key to a server; a search secret key decryption step of the terminal decrypting the encrypted search secret key acquired from the server to obtain the search secret key; an encrypted message transmission step of the terminal transmitting an index set generated using information related to a message and a newest search secret key, and an encrypted message to the server; a query transmission step of the terminal transmitting a query set generated using a message search character string and the search secret key; and an encrypted message returning step of the server transmitting an encrypted message including elements of an index set corresponding to an element of the query set.

Encrypted message search method, message transmission/reception system, server, terminal and program

A communication terminal shares a session key with and sends cipher text to another communication terminal via a server device, including: a common key cipher text obtaining unit that encrypts a message based on a common key to obtain common key cipher text; a function computation result obtaining unit that computes the common key and the session key based on a predetermined first function to obtain a function computation result; a public key cipher text obtaining unit that encrypts the function computation result based on a public key to obtain public key cipher text; and a cipher text sending unit that sends the common key cipher text and the public key cipher text to the server device. The communication terminal can update data previously saved in a server to data that can be decrypted on the communication terminal side using an updated session key, without the server decrypting the data.

Communication terminals, server devices, and programs

There is provided a data sharing technique in which it is possible to update data stored in a server before to such data that is decryptable on the communication terminal side using an updated session key without the data being decrypted on the server side, and a deleted user cannot decrypt the decryptable data. There are included: a generation identifier generation step of a data sharing server generating a generation identifier showing a generation of a group; a session key encryption step of a communication terminal to perform encrypted session key update using the generation identifier received from the data sharing server and a public parameter and a session key recorded in a recording part to generate an encrypted session key, which is a session key encrypted; and an encrypted session key management step of the data sharing server recording the encrypted session key received from the communication terminal to perform encrypted session key update as a currently valid encrypted session key.

Growing community of inventors

Musashino, Japan

Yuki Okano