Kabushiki Kaisha Toshiba

Alex Dixon

Yoshimichi Tanizawa

Hideaki Sato

Ririka Takahashi

Kazuaki Doi

Akira Murakami

A transmitting device according to an embodiment include a transmission unit, a storage unit, a cache unit, a reception unit, and a sifting processing unit. The transmission unit transmits a transmission photon to a receiving device. The storage unit stores transmission photon information including transmission timing at which the transmission photon is transmitted, a transmission bit indicated by the transmission photon, and a transmission base of the transmission photon. The cache unit stores, one or more pieces of transmission information including the transmission timing after an elapse of a no-use period of the transmission photon. The reception unit receives, from the receiving device, the reception timing and a reception base of the reception photon. The sifting processing unit performs sifting processing on the transmission bit by making a correlation between the transmission base and the reception base on the basis of the reception timing and the transmission timing.

Transmitting device, quantum communication system, and quantum communication method

According to an embodiment, a communication device is connected to another communication device through a quantum communication channel and a classical communication channel to share an encryption key. The device includes a photon detector, a measurer, a difference generator, and a transmitter. The photon detector is configured to detect photons transmitted from the other communication device through the quantum communication channel. The measurer is configured to measure time when each photon is detected by the photon detector as time stamp information. The difference generator is configured to generate difference time stamp information as a difference between time obtained by adding particular information to the time indicated by the time stamp information previously measured by the measurer and time indicated by the time stamp information subsequently measured by the measurer. The transmitter is configured to transmit the difference time stamp information to the other communication device through the classical communication channel.

Communication device, quantum key distribution system, quantum key distribution method, and computer program product

According to an embodiment, a communication device is connected to another communication device through an optical communication path to generate an identical cryptographic key shared among the communication devices. The communication device includes a key sharing unit, a key distilling unit, a measuring unit, and a varying unit. The key sharing unit is configured to generate a shared bit string through quantum key distribution with the another communication device. The key distilling unit is configured to generate the cryptographic key from the shared bit string by a key distillation process. The measuring unit is configured to measure an error rate occurring in a photon string transmitted and received via a photon communication channel. The varying unit is configured to vary, based on the error rate, a communication function by applying a limitation on the optical data communication of an optical data communication channel or by releasing the limitation.

Communication device, communication system, and communication method

According to an embodiment, a transmitter transmits first transmission key data and second transmission key data as quantum information. The transmitter includes a first privacy amplifier and a second privacy amplifier. The first privacy amplifier generates first secure key data by performing privacy amplification to remove information that has possibly been acquired by an eavesdropper of the first transmission key data on the first transmission key data. The second privacy amplifier generates second secure key data by performing the privacy amplification to remove information that has possibly been acquired by the eavesdropper of the second reception key data on the decoded key data.

Transmitter, receiver, quantum key distribution (QKD) system and quantum key distribution method

According to an embodiment, a communication apparatus includes a cryptographic key storage, a transmitter, a receiver, and a sharing controller. The cryptographic key storage stores therein one or more cryptographic keys shared with an external device. The transmitter transmits specifying information that specifies at least one of the cryptographic keys to the external device. The receiver receives determination information that indicates a result of determination, which is made by the external device based on the specifying information, on whether the shared cryptographic key is consistent between the apparatus and the external device. When receiving the determination information indicating that the shared cryptographic key is inconsistent between the apparatus and the external device, the sharing controller deletes the cryptographic key specified by the specifying information from the cryptographic key storage.

Communication apparatus, computer program product, and communication system

According to one embodiment, a transmitter includes a signal dividing unit, a syndrome sending unit, a syndrome receiving unit and a decoding unit. The signal dividing unit divides an original signal into a first signal and a second signal based on a common dividing policy. The syndrome sending unit sends the first syndrome message calculated based on the first signal through a clear channel. The syndrome receiving unit receives a second syndrome message through the clear channel. The decoding unit decodes the second signal by using the second syndrome message to restore a fourth signal, the fourth signal being corresponding to the second signal received by a receiver through a noisy channel.

Growing community of inventors

Kawasaki, Japan

Alex Dixon