Patent US5764765A successfully refreshed from Google Patents.
US5764765A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for key distribution using quantum cryptography
Assignee: British Telecommunications PLC
•
Filing: 1994-09-08
•
Granted: 1998-06-09
•
Expires: 2014-09-08
Abstract
Abstract In a communication system using quantum cryptography for the distribution of a key, two stations each independently modulate a single-photon signal. The single-photon signal is transmitted to the two stations from an external source, and passes through the stations in series. The signal subsequently passes onto a third station which detects the state of the signal, and compares it with the state of the signal as originally transmitted. This third station communicates the results of the comparison to the two stations, and the two stations establish a shared secret key for the subsequent encryption of traffic between the stations. Both the source of the single-photon signal and the single-photon detector may be combined in a transmitter station (Alice).
Inventors
- 👤 Simon James Phoenix
- 👤 Stephen Mark Barnett
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 13:33
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/08; H04L9/0816; H04L9/0852; H04L9/0858
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
89 words
A method of communication using quantum cryptography characterised in that two stations (Bob(1), Bob(2)) each independently modulate a single-photon signal transmitted from an external source to both the stations in series, the said signal subsequently passing on to a third station which detects the state of the signal, compares it with the state of the signal as originally transmitted, and communicates the results of the comparison to the two stations, the two stations thereby establishing a shared secret key for the subsequent encryption of traffic between the two stations.
Claim 2
Independent Claim
89 words
A method of communication using quantum cryptography characterised in that two stations (Bob(1), Bob(2)) each independently modulate a single-photon signal transmitted from an external source to both the stations in series, the said signal subsequently passing on to a third station which detects the state of the signal, compares it with the state of the signal as originally transmitted, and communicates the results of the comparison to the two stations, the two stations thereby establishing a shared secret key for the subsequent encryption of traffic between the two stations.
Claim 3
Dependent Claim
57 words
A method of communication according to claim 1, in which the third station (Alice) includes the source for the single-photon signal and transmits the signal from the source encoded in a predetermined phase or polarisation state, and includes a single-photon detector and measures the state of the single-photon signal as returned from the two stations (Bob(1), Bob(2)).
Claim 4
Dependent Claim
30 words
A method according to claim 2, in which the single-photon signal is transmitted on a network including a looped-back path from the two stations (Bob(1), Bob(2)) to the transmitter (Alice).
Claim 5
Dependent Claim
72 words
A method according to claim 1, in which there are a multiplicity of stations (Bob(1), Bob(2) . . . Bob(N)) connected to the transmitter station by a common communications network, the method further comprising an initial contention step in which a selected two of the multiplicity of stations (Bob(1), Bob(2) . . . Bob(N)) establish an exclusive right to use specific transmissions of the single-photon signal for establishing a mutual secret key.
Claim 6
Dependent Claim
31 words
A method according to claim 1 including a step of comparing with a predetermined threshold statistics of rejected data determined to have been modulated by the two stations using different operators.
Claim 7
Dependent Claim
118 words
A communications system comprising a communications network arranged to carry a quantum channel, a single-photon source arranged to output single-photon signals onto the network, at least two stations (Bob(1), Bob(2)) connected to the network and each including a modulator arranged to modulate in series the single-photon signal and a third station (Alice) including a single-photon detector arranged to detect the single-photon signal after its modulation by the at least two stations (Bob(1), Bob(2)), in use the third station (Alice) comparing the state of the single-photon signal as received with the state of the signal as originally transmitted and communicating the result of the comparison to the two stations, and the two stations establishing thereby a shared secret key.
Claim 8
Dependent Claim
118 words
A communications system comprising a communications network arranged to carry a quantum channel, a single-photon source arranged to output single-photon signals onto the network, at least two stations (Bob(1), Bob(2)) connected to the network and each including a modulator arranged to modulate in series the single-photon signal and a third station (Alice) including a single-photon detector arranged to detect the single-photon signal after its modulation by the at least two stations (Bob(1), Bob(2)), in use the third station (Alice) comparing the state of the single-photon signal as received with the state of the signal as originally transmitted and communicating the result of the comparison to the two stations, and the two stations establishing thereby a shared secret key.
Claim 9
Dependent Claim
21 words
A system according to claim 6, in which the third station (Alice) includes both the single-photon source and the single-photon detector.
Claim 10
Dependent Claim
25 words
A system according to claim 7, in which the network includes a looped-back path from the two stations (Bob(1), Bob(2)) to the third station (Alice).
Claim 11
Dependent Claim
29 words
A system according to claim 6, in which a multiplicity of stations (Bob(1), Bob(2) . . . Bob(N)) are connected to the transmitter station by a common communications network.
Claim 12
Dependent Claim
60 words
A system according to claim 9, in which each of the multiplicity of stations (Bob(1), Bob(2) . . . Bob(N)) is responsive to control signals transmitted by Alice in an initial contention step to leave unmodulated a single-photon signal reserved for establishing a mutual secret key between two other of the multiplicity of stations (Bob(1), Bob(2) . . . Bob(N)).
Claim 13
Dependent Claim
16 words
A system according to claim 6, in which the communications network is an optical-fibre based LAN.
Claim 14
Dependent Claim
14 words
A transmitter station (Alice) adapted for use in a system according to claim 6.
Claim 15
Dependent Claim
19 words
A receiver station (Bob(1), Bob(2) . . . Bob(N)) adapted for use in a system according to claim 6.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-06-08 | 2001-12-08 | 2002-06-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-06-08 | 2005-12-08 | 2006-06-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-06-08 | 2009-12-08 | 2010-06-09 | $7700.00 | Window Closed / Lapsed |