Abstract: 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.

Abstract: According to an embodiment, a communication device includes an acquirer and a determiner. The acquirer is configured to acquire a first history value for each of one or more applications that use an encryption key. The first history value indicates a history value of a volume of the encryption key used by the each of one or more applications. The determiner is configured to determine a volume of the encryption key to be assigned to the corresponding application, according to the first history value.

Abstract: 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.

Abstract: According to an embodiment, a communication device includes a storage, a receiver, a storage controller, an allocator, and an encryption processor. The storage has a predetermined number of storage areas capable of storing one or more shared keys shared with a destination device. The receiver is configured to receive a shared key. The storage controller is configured to store the received shared key in any of the storage areas every time the shared key is received. The allocator is configured to allocate the storage areas to communication channels used for communicating encrypted data between the communication device and the communication destination device, based on a ratio predetermined for each communication channel. The encryption processor is configured to, according to a cryptosystem determined for the each communication channel, encrypt data and decrypt the encrypted data by using the shared key acquired from the storage area allocated to each communication channel.

Abstract: A communication device includes a plurality of key distributing units, a plurality of communicating units, a monitoring unit, and a switching unit. The plurality of key distributing units have a quantum key distribution function for sharing a quantum key with an external distribution device. The plurality of communicating units communicate with an external communication device using the quantum key. The monitoring unit monitors operational status indicating at least one of transmission-reception status of photons in the quantum key distribution function, generation status of generating the quantum key, and obtaining status of obtaining the quantum key. The switching unit switches a control target, which either represents one of the key distributing units or represents one of the communicating units, from a first control target to a second control target other than the first control target according to the operational status.

Abstract: According to an embodiment, a communication device includes a receiver, an allocator, a first communication unit, an encryption processor, a second communication unit, and a controller. The receiver is configured to receive a shared key shared with another device. The allocator is configured to allocate the shared key to a transmission key or a reception key. The first communication unit is configured to receive data from an application. The encryption processor is configured to encrypt the data with the transmission key and decrypt the data encrypted by the other device with the reception key. The second communication unit is configured to communicate with the other device by using the encrypted data. The controller is configured to control at least one of allocation of the shared key, traffic of the first communication unit, and traffic of the second communication unit, by using state information of the device.

Abstract: A communication device includes a providing unit, a flow control unit, and a cryptography processing unit. The providing unit provides a cryptographic key generated using quantum key distribution technology. The flow control unit, if the cryptographic key has not been provided at time of reception of target data for cryptography processing, performs, with respect to the received data, an operation selected from among a first operation of destroying the data, a second operation of holding the data, and a third operation of attaching, to the data, information indicating that the cryptographic key has not been provided, and then outputting the data. The cryptography processing unit, with respect to data output from the flow control unit, performs the cryptography processing using the cryptographic key.

Abstract: 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.

Abstract: According to an embodiment, a receiver is connected to transmitters through photon communication channels and data communication channels to generate identical cryptographic keys to be shared with each transmitter. The receiver includes a sharing unit, a key distilling unit, a data communication controller, and a calculator. The key sharing unit is configured to generate a shared bit string through quantum key distribution with each transmitter via a corresponding photon communication channel. The key distilling unit is configured to generate the cryptographic keys from the respective shared bit strings. The data communication controller is configured to receive from each transmitter first information about a corresponding cryptographic key via a corresponding data communication channel. The calculator is configured to calculate the photon timeslots based on at least the first information. The data communication controller is configured to transmit the photon timeslots to the transmitters.

Abstract: 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.

Abstract: According to an embodiment, a quantum key distribution device includes a quantum key distributor, a sifter, a corrector, an identifier, a classifier, a calculator, and a privacy amplifier. The quantum key distributor obtains a photon string from a photon string of two or more intensities of light pulses. The sifter obtains pulse information indicating the light pulse to which each bit of a shared bit string corresponds. The corrector corrects an error included in the shared bit string and generates a post-correction bit string. The identifier generates error position information. The classifier classifies each bit of the post-correction bit string. The calculator calculates the error rate for each light pulse and each base using the error position information. The privacy amplifier generates a cryptographic key from the post-correction bit string on the basis of the error rate.

Abstract: A communication device in embodiments is a quantum key distribution device connectable to another quantum key distribution device through a quantum communication channel to share an encryption key therebetween, and includes a common processing unit, one or more individual processing units, and a distribution unit. The common processing unit outputs intermediate data based on bit information obtained by transmitting or receiving sequence of photons with the another quantum key distribution device through the quantum communication channel. Each individual processing unit generates or provides the encryption key in accordance with the intermediate data. The distribution unit distributes the intermediate data that is output from the common processing unit to two or more distribution destination that include the individual processing units.

Abstract: According to an embodiment, a communication device is connected with another communication device through a quantum communication channel with a shared encryption key. The device includes a communication unit, a sifter, a corrector, a calculator, and an extractor. The communication unit is configured to acquire a sequence of photons through the quantum communication channel and acquire a photon bit string corresponding to the sequence of photons. The sifter is configured to generate a shared bit string from the photon bit string by sifting processing using basis information. The corrector is configured to generate a corrected bit string by correcting an error included in the shared bit string. The calculator is configured to generate a hash-calculated bit string by performing hash calculation on the corrected bit string. The extractor is configured to extract, as the key, from the hash-calculated bit string, a bit string having the length of the key.

Abstract: According to an embodiment, a quantum key distribution device includes a sharer, a key distillation processor, a first manager, and a second manager. The sharer is configured to share a photon string with the another quantum key distribution device using quantum key distribution via a quantum distribution channel, and obtain a photon bit string corresponding to the photon string. The key distillation processor is configured to generate a link key from the photon bit string. The first manager is configured to store the link key as a link transmission key. The second manager is configured to store, in a storage, a first application key from an application key to be used in cryptographic data communication, encrypt a second application key from the application key, using the link transmission key, and send the encrypted second application key to another quantum key distribution device via a classical communication channel.

Abstract: According to a communication device includes a sharing processing unit, a storage, and a controller. The sharing processing unit shares an encryption key with one or more external devices. The storage stores therein the encryption key. The controller compares a current amount representing an amount of the stored encryption key with a specified reference amount and performs control to continue or stop sharing processing, which is performed by the sharing processing unit, for sharing the encryption key on the basis of a comparison result.

Abstract: A communication device according to an embodiment is a communication device that communicates with another communication device using an encryption key shared through a quantum key distribution and includes a communication unit, an encrypting unit, a first checking unit, and a communication control unit. The communication unit performs communication of data with the another communication device. The encrypting unit encrypts data using the encryption key. The first checking unit checks an accumulation amount of the encryption key. The communication control unit control transmission of dummy data according to checked results.

Abstract: According to an embodiment, a quantum communication device includes a sift processor, an estimator, a determination unit, and a corrector. The sift processor is configured to acquire sift processing data by referring to a cryptographic key bit string in a predetermined bit string with a reference basis randomly selected from a plurality of bases via a quantum communication channel. The estimator is configured to acquire an estimated error rate of the sift processing data. The determination unit is configured to determine order of the sift processing data in which an error is to be corrected based on the estimated error rate and difference data between a processing speed of error correcting processing and a processing speed of privacy amplification processing. The corrector is configured to acquire one piece of the sift processing data in the order determined by the determination unit, and generate error correcting processing data.

Abstract: According to an embodiment, a quantum communication device includes a receiver, a sift processor, an estimator, first and second storages, a determination unit, an error corrector, a measurement unit, and a privacy amplifier. The sift processor acquires sift processing data by referring to a cryptographic key bit string in a predetermined bit string with a reference basis randomly selected from a plurality of bases. The estimator acquires an estimated error rate by estimating an error rate of the sift processing data from an error rate of part of the sift processing data. When a sift processing data volume stored in the first storage is not smaller than a first threshold, the determination unit determines order of the sift processing data to be corrected based on an estimated error rate, an error rate range that a check matrix can correct, and estimated correction time, and the check matrix used for correction.

Abstract: A first determining unit determines a period of time during which there is possibility of wiretapping of data present in a data communication channel connected to another communication device. A second determining unit determines, with a length of the period of time as unit of time, size of a cryptographic key used for encrypting data to be transmitted to the other communication device via the data communication channel during each unit of time. A first obtaining unit obtains a first cryptographic key having the size, from a first storing unit storing therein cryptographic keys shared with the other communication device. A recognizing unit recognizes possibility of wiretapping with respect to the data communication channel. Until the possibility of the wiretapping is recognized, a encrypting unit repeatedly encrypts data to be transmitted to the other communication device during each unit of time using the first cryptographic key.

Abstract: According to an embodiment, a receiver is connected to transmitters through photon communication channels and data communication channels to generate identical cryptographic keys to be shared with each transmitter. The receiver includes a sharing unit, a key distilling unit, a data communication controller, and a calculator. The key sharing unit is configured to generate a shared bit string through quantum key distribution with each transmitter via a corresponding photon communication channel. The key distilling unit is configured to generate the cryptographic keys from the respective shared bit strings. The data communication controller is configured to receive from each transmitter first information about a corresponding cryptographic key via a corresponding data communication channel. The calculator is configured to calculate the photon timeslots based on at least the first information. The data communication controller is configured to transmit the photon timeslots to the transmitters.