We have developed an optical key distribution scheme where communicators are able to generate identical binary keys from a wideband optical phase-noise-bearing lightwave. In our scheme, a phase-noise-bearing lightwave is distributed among the communicators via optical fiber, and then converted an intensity modulation by an unequal path length interferometer and converted to a binary stream by a comparator. The use of a broadband noisewave (>100GHz, ~0.8nm at 1550 nm), precludes the possibility of an eavesdropper recording the signal in enough detail to analyze the noise in conjunction with the encrypted data processing. Corresponding intensity modulations are produced if both interferometers have the same pathlength inequality to within a certain tolerance. We have demonstrated identical key generation by two independent terminals receiving a distributed optical noisewave for bit positions designated with a good validity bit. A separate Ethernet link between the terminals was used to assess the quality of the binary key generation. The system uses three WDM optical channels to transmit the noisewave at 1550 nm, data at 1310 and a probe signal for interferometer stabilization at 1530nm.
We have developed an optical key distribution scheme where communicators are able to generate identical binary keys from a wideband optical phase-noise-bearing lightwave. In our scheme, a phase-noise-bearing lightwave is distributed among the communicators via optical fiber, and then converted an intensity modulation by an unequal path length interferometer and converted to a binary stream by a comparator. The use of a broadband noisewave (>100GHz, ~0.8nm at 1550 nm), precludes the possibility of an eavesdropper recording the signal in enough detail to analyze the noise in conjunction with the encrypted data processing. Corresponding intensity modulations are produced if both interferometers have the same pathlength inequality to within a certain tolerance. We have demonstrated identical key generation by two independent terminals receiving a distributed optical noisewave for bit positions designated with a good validity bit. A separate Ethernet link between the terminals was used to assess the quality of the binary key generation. The system uses three WDM optical channels to transmit the noisewave at 1550 nm, data at 1310 and a probe signal for interferometer stabilization at 1530nm.
We propose and experimentally demonstrate an approach to generate and distribute secret keys over optical fiber communication infrastructure. Mach-Zehnder interferometers (MZIs) are adopted for key generation by transferring the environmental noise to random optical signals. A novel combination of wideband optical noise and an asymmetric MZI structure enables the secret keys to be securely transmitted and exchanged over public fiber links without being detected. We experimentally demonstrate this system and show reliable performance: keys are generated at the rate of 502 bit/s, and are successfully exchanged between two parties over a 10 km optical fiber with a bit error of ∼ 0.3%. System security analysis is performed by corroborating our experimental findings with simulations. The results show that our system can protect the key distribution under different attacks, attributed to wideband optical noise and asymmetric MZI structures. Compared to the previous schemes based on distributed MZIs, our scheme exploits localized MZI which provides twofold advantages. Firstly, the key generation rate can be increased by a factor of 5.7 at a negligible additional cost. Secondly, the system becomes robust to, in particular, active intrusion attack. The proposed system is a reliable and cost-effective solution for key establishment, and is compatible with the existing optical fiber communication infrastructure.
In this paper, a secure key generation and distribution scheme based on the phase noise of an amplified spontaneous emission source is proposed and experimentally verified. A giant key generator that contains two distribution arms is used to generate a specific beat dependent on the path length difference of the arms. Through the method of balanced subtraction of the local signals, the effect of the intensity noise has been mainly excluded, and the two legal users obtain the consistent differential signal that depended on the phase noise. Experiment results show that the correlation coefficient of the key signals reaches to about 0.89, and the bit generation rate of the scheme achieves to 3.06 Gbit/s under a length of 20 km standard single-mode optical fiber route, as the bit error rate stays under 0.02%. Moreover, the converted digital key stream has passed the NIST statistical test suite, which means that the scheme is inherently random in the statistical sense. With the excellent performance mentioned above, the proposed scheme provides a simple and efficient solution for the method of one-time pad.
Keeping in mind the ubiquitous standard optical fiber for long‐distance transmission and the widespread availability of efficient active and passive fiber devices, we have been developing telecom‐band resources for practical quantum communication and cryptography in wave‐division‐multiplexed (WDM) optical networks. In this talk I present our recent results on two fronts: i) telecom‐band in‐fiber entanglement generation, storage, and long‐distance distribution and ii) quantum‐noise protected high‐speed data encryption through an optically‐amplified WDM line. Along the first front, with our in‐fiber entanglement source all four Bell states can be readily produced and we have demonstrated violation of Bell’s inequalities by up to 10 standard deviations of measurement uncertainty. With such a source we have demonstrated storage of entanglement for up to 1/8 of a millisecond. Furthermore, when each photon of the entangled pair is propagated in separate 25km‐long standard fibers, high visibility quantum interference is still observed, demonstrating that this system is capable of long‐distance (> 50 km) entanglement distribution. Along the second front, we have implemented a new quantum cryptographic scheme, based on Yuen’s KCQ protocol, in which the inherent quantum noise of coherent states of light is used to perform the cryptographic service of data encryption. In this scheme a legitimate receiver, with use of a short, shared, secret‐key, executes a simple binary decision rule on every transmitted bit. An eavesdropper, on the other hand, who does not possess the secret‐key, is subjected to an irreducible quantum uncertainty in each measurement, even with the use of ideal detectors. We have implemented this scheme to demonstrate quantum‐noise‐protected data encryption at 650 Mbps through a 200 km, in‐line amplified, WDM line. The line simultaneously carried two 10 Gbps standard data channels, 100 GHz on either side of the encrypted channel, which shows that this scheme is compatible with the widely deployed WDM fiber‐optic infrastructure.
We propose a secure key generation and distribution scheme for data encryption in classical optical fiber channel. A Delay interferometer (DI) is used to track the random phase fluctuation inside fiber, while the reconfigurable lengths of polarization-maintaining (PM) fiber are set as the source of optical phase fluctuations. The output signals from DI are extracted as the secret key and shared between the two-legal transmitter and receiver. Because of the randomness of local environment and the uniqueness of fiber channel, the phase fluctuation between orthogonal polarization modes (OPMs) can be used as secure keys to enhance the level of security in physical layer. Experimentally, we realize the random key generation and distribution over 25-km standard single-mode fiber (SSMF). Moreover, the proposed key generation scheme has the advantages of low cost, compatible with current optical fiber networks and long distance transmission with optical amplifiers.
We describe an experimental laboratory system that generates and distributes random binary sequence bit streams between two optical terminals (labeled Alice and Bob). The random binary sequence is generated through probing the optical channel of a turbulent atmosphere between the two terminals with coincident laser beams. The two laser beams experience differential phase delays while propagating through the atmospheric optical channel. The differential phase delays are detected and sampled at each terminal to yield raw random bit streams. The random bit streams are processed to remove bit errors and, through privacy amplification, to yield a bit stream known only to Alice and Bob. The same chaotic physical mechanism that provides randomness also provides confidentiality. The laboratory system yielded secret key bit rates of a few bits/second . For external optical channels over longer channel lengths with atmospheric turbulence levels, secret bit rates of 10 s of bits/second are predicted.
This paper proposes a novel key distribution system based on the measurement of the bit error rate (BER) in a fiber channel. By carrying out the loopback BER measurement at both the transmitting and the receiving end, the BER is quantified and codified to generate consistency keys. Alice and Bob respectively encrypt the signal with the help of the public key base at the transmitting end. At the receiving end the data are decrypted and then the BER is measured. The security of generated keys in the system is enhanced by the use of the encryption base and the randomness of the channel. Additionally, noise sources are added to the channel so that the random noise conceals signals and Eve cannot eavesdrop the useful information in it. Due to the randomness of the channel noise, the generated keys have good randomness. This system at a high key generation rate is compatible with the existing communication device and its measurement is simple. The 10G bit/s-200 km coherent optical communication system is used to measure the BER of the security feature information of the extracted channel. The experimental results show that the key distribution system obtains a consistency rate of 98% with the key generation rate 2 Mbps, both of which have been significantly improved.