Nippon Telegraph and Telephone Corporation

Tsunekazu Saito

Tetsutaro Kobayashi

Akira Nagai

Atsushi Nakadaira

Shigeru Fujimura

Hiroki Watanabe

Go Yamamoto

Shigenori Ohashi

Koutarou Suzuki

Yuki Okano

Koha Kinjo

A key exchange system method safely conceal secret information recorded on a blockchain. A first terminal includes a license issuing unit that generates a first transaction including a first public key, a first key storage region that retains a first secret key, and a first encrypting and decrypting unit that generates a common key using deal-specific information, a second public key, and the first secret key, and a second terminal includes a license requesting unit that generates a second transaction including the second public key, a second key storage region that retains a second secret key, and a second encrypting and decrypting unit that generates the common key using deal-specific information, the first public key, and the second secret key. The first encrypting and decrypting unit encrypts secret information using the common key. The second encrypting and decrypting unit decrypts the encrypted secret information using the common key.

Key exchange system and key exchange method

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

Registered network-based identification corresponding to any of networks is stored in a key device. A terminal devicesends ciphertext and network-based identification to the key device, using a network. The key devicereceives the sent ciphertext and network-based identification and outputs response information corresponding to a decrypted value of the ciphertext when the network-based identification corresponds to the registered network-based identification. The terminal deviceobtains the decrypted value from the response information.

Key device, key cloud system, decryption method, and program

A random number generating unit generates random numbers s, s, s', and s&#x2032;. A public keys randomizing unit generates first randomized public keys information obtained by randomizing public keys using the random number sand second randomized public keys information obtained by randomizing the public keys using the random number s. A proxy calculation unit calculates a first commission result by using a secret key and calculates a second commission result by using the secret key. A verification unit calculates a first verification value by using the random number s, calculates a second verification value by using the random number s, and verifies whether or not the first verification value and the second verification value coincide with each other. A common key calculation unit calculates a common key by using the random numbers s&#x2032;and s&#x2032;if the first verification value and the second verification value coincide with each other.

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

Growing community of inventors

Musashino, Japan

Tsunekazu Saito