Abstract: A system for extracting data from a plurality of electromagnetic data signals encoding the data is provided. The system includes a phase modulator which receives an electromagnetic beam, and generates an electromagnetic primary reference beam with a defined phase. The system further includes one or more mixing units, each mixing unit being arranged to receive a respective one of the data signals and a reference beam, and to generate two mixed signals. The one or more mixing units include a first mixing unit for which the reference beam is the primary reference beam. The system also includes a plurality of detection units. Each detection unit is arranged to receive a respective one of the data signals and a respective mixed signal from one of the mixing units, and to obtain a difference measurement indicative of a difference between the respective data signal and the respective mixed signal.

Abstract: A system for extracting data from a plurality of electromagnetic data signals encoding the data is provided. The system includes a phase modulator which receives an electromagnetic beam, and generates an electromagnetic primary reference beam with a defined phase. The system further includes one or more mixing units, each mixing unit being arranged to receive a respective one of the data signals and a reference beam, and to generate two mixed signals. The one or more mixing units include a first mixing unit for which the reference beam is the primary reference beam. The system also includes a plurality of detection units. Each detection unit is arranged to receive a respective one of the data signals and a respective mixed signal from one of the mixing units, and to obtain a difference measurement indicative of a difference between the respective data signal and the respective mixed signal.

Abstract: In carrying out a task that consumes data from a one-time pad, task inputs comprising at least first data and second data from the pad, are combined together to form an output from which the data used from the pad cannot be recovered without knowledge of at least one of the first and second data. The task concerned can be, for example, the encrypting of a message or the creating of an attribute verifier.

Abstract: A device is arranged to carry out security-related tasks using one-time pad data. The device has a memory for holding multiple one-time pads, each pad having a different security rating and being intended for use by the device in executing a task to that security rating. Provisioning of the pads with one-time pad data involves carrying out a process for obtaining new secret random data. This process has a security rating with the value of this rating varying according to the nature and parameters of the process concerned. The security rating of the process used to obtain the new secret random data is matched to that of the pad to be provisioned with one-time data, or the other way around, such that the security rating of the process is as least as good as that of the pad to be provisioned.

Abstract: Secret random data is distributed to a plurality of devices to provision them with new one-time pad data for use in interacting with apparatus holding the same one-time pad data. This distribution is effected by provisioning a first device with a block of secret random data that is, or will become, available to the apparatus. Part of the secret random data is then distributed from the first device to one or more other devices in a hierarchical distribution pattern headed by the first device. Each device, other than those at the bottom of the distribution hierarchy, retains part of the secret random data it receives and passes on the remainder. Each device uses that part of the secret random data it has retained to provide the device with new one-time pad data. A method is also provided for tracking service usage based on the distributed one-time pad data.

Abstract: A device stores one-time pad data for use in carrying out various tasks. In order to preserve the ability to carry out important tasks that require the use of one-time data, use of the one-time pad data held by the device is controlled such that an amount of this one-time pad data is only usable by a predetermined set of important tasks comprising at least a replenishment task for replenishing the device with one-time pad data.

Abstract: A method of establishing a shared secret random cryptographic key between a sender and a recipient using a quantum communications channel is described.

Abstract: Various method and system embodiments of the present invention are directed to executing bit-commitment protocols. In one embodiment of the present invention, a method for executing a bit-commitment protocol for transmitting a bit from a first party to a second party comprises preparing a three qubits are entangled in a W-state, and storing a first of the three qubits in a first storage device controlled by the first party, a second of the three qubits is stored in a second storage device controlled by the second party, and a third of the three qubits is stored in a third storage device controlled by a third party. The bit is revealed to the second party by transmitting the first and third qubits to the second party and measuring the states of the three qubits to which of the entangled W-states the three qubits are in.

Abstract: Various method and system embodiments of the present invention are directed to executing bit-commitment protocols. In one embodiment of the present invention, a method for executing a bit-commitment protocol for transmitting a bit from a first party to a second party comprises preparing a three qubits are entangled in a W-state, and storing a first of the three qubits in a first storage device controlled by the first party, a second of the three qubits is stored in a second storage device controlled by the second party, and a third of the three qubits is stored in a third storage device controlled by a third party. The bit is revealed to the second party by transmitting the first and third qubits to the second party and measuring the states of the three qubits to which of the entangled W-states the three qubits are in.

Abstract: A device is arranged to carry out security-related tasks using one-time pad data. The device has a memory for holding multiple one-time pads, each pad having a different security rating and being intended for use by the device in executing a task to that security rating. Provisioning of the pads with one-time pad data involves carrying out a process for obtaining new secret random data. This process has a security rating with the value of this rating varying according to the nature and parameters of the process concerned. The security rating of the process used to obtain the new secret random data is matched to that of the pad to be provisioned with one-time data, or the other way around, such that the security rating of the process is as least as good as that of the pad to be provisioned.