Recently, Jiang et al. proposed a novel quantum multi-signature protocol based on locally indistinguishable orthogonal product states. Unfortunately, their protocol cannot resist against the forgery ...attack and disavowal attack. We investigate the security of Jiang et al.’s quantum multi-signature protocol and demonstrate the signature receiver’s forgery attack. What is more, the signature receiver can extend the forgery attack such that anyone can generate the forgery. On the other hand, their protocol is insecure against the signers’ disavowal attack, too. Then, an improved quantum multi-signature protocol is proposed. In the improved protocol, all the signers share the private keys with the signature receiver and the arbitrator. To generate a quantum multi-signature, all the signers perform the unitary operations controlled by the private keys and the message. The improved protocol overcomes all the security drawbacks of Jiang et al.’s quantum multi-signature. What is more, the arbitrator Trent can be semi-trusted, because he cannot forge any quantum signature of the signers, although Trent shares the private keys with all the signers. At the same time, the new protocol has the same quantum efficiency as that of Jiang et al.’s protocol.
We have theoretically investigated the transmission performance of the optical millimeter-waves (mm-waves) generated using intensity modulation via a Mach-Zehnder modulator, with the double and ...single sidebands (DSB and SSB) and optical carrier suppression (OCS) schemes. According to our theoretical analysis, fiber chromatic dispersion leads to fading effect and time shifting of the codes; therefore, signals are greatly degraded. Of all signals, DSB optical mm-wave suffers from both the fading effect and the time shifting of the codes. However, the optical mm-waves generated by SSB and OCS schemes are immune to the fading effect, while the time shifting of the codes limits their transmission distance. Experimental and simulation results confirm the theoretical analysis.
In this paper, a novel turbo-coded 16-ary orbital angular momentum - shift keying-free space optical (OAM-SK-FSO) communication system combining a convolutional neural network (CNN) based adaptive ...demodulator under strong atmospheric turbulence is proposed for the first time. The feasibility of the scheme is verified by transmitting a 256-grayscale two-dimensional digital image. The bit error ratio (BER) performance of the system is investigated and the effect of different factors such as turbulence strength, propagation distance, code rate, length of random interleaver and length of bit interleaver is also taken into account. An advanced encoder/decoder structure and mapping scheme are applied to diminish the influence of CNN misclassification and reduce the BER effectively. With the optimal encoder/decoder structure and CNN model settings, the BER varies from 0 to 4.89×10
when the propagation distance increases from 200m to 1000m for a given turbulence strength Cn2 equals 5×10
m
. For a determined propagation distance equals 400m, the BER ranges from 0 to 4.01×10
when Cn2increases from 1×10
m
to 4×10
m
. Our numerical simulations demonstrate that the proposed system can provide better BER performance under strong atmospheric turbulence and conditions when the classification ability of CNN is limited.
Existing wavefront sensorless (WFS-less) adaptive optics (AO) generally require a search algorithm that takes lots of iterations and measurements to get optimal results. So the latency is a serious ...problem in the current WFS-less AO system, especially in applications to free-space optics communication. To solve this issue, we propose a deep neural network (DNN)-based aberration correction method. The DNN model can detect the wavefront distortion directly from the intensity images, thereby avoiding time-consuming iterative processes. Since the tip-and-tilt mode of Zernike coefficients are considered, the tip-tilt correction system is not necessarily required in the proposed method. From our simulation results, the proposed method can effectively reduce the computation time and has an impressive improvement of root mean square (RMS) in different turbulence conditions.
Quantum Signature without Classical Private Key Chen, Mingcan; Xin, Xiangjun; Chen, Dongsheng
International journal of theoretical physics,
02/2022, Letnik:
61, Številka:
2
Journal Article
Recenzirano
Generally, in a quantum signature protocol, the signature is produced with the signatory’s classical private key, which is a secret bit string. In most of the signature schemes, it is assumed that ...the classical private keys are secretly kept. However, in practice, the protection of the classical private key may be vulnerable to various special attacks such as side channel attack, power analysis and cool boot attack. The classical private key may also be disclosed due to the mismanagement of its owner and distributor. Once the signatory’s private key is disclosed, the quantum signature system can be broken. In this paper, a novel quantum signature scheme without classical private key is proposed. In this protocol, the signatory and the trusted third party share the Bell states. The signatory signs a message with the Bell states rather than classical private key. The quantum signature is verified with the Bell states as well. Therefore, it is impossible for any quantum adversary to forge a particle by getting some information about the classical private key. The security of our scheme fully relies on the quantum property of the physical particle. Our scheme can resist against various attacks such as forgery attack, disavowal attack, inter-resending attack and measurement attack. Our signing protocol has the better qubit efficiency than the similar ones.
Semi-quantum signature is an important research topic in quantum cryptography. Based on the Bell states, a semi-quantum signature scheme with arbitrator is proposed. In our scheme, the quantum signer ...signs the message by encoding the ciphtext with the Bell states and performing the controlled NOT gate on the particles, while the signature receiver and arbitrator corporately verify the signature by measuring the received qubits with Z-basis. Compared with the similar schemes, ours has the better performances as follows. (1) It can be proved to be information-theoretically secure. It has the strong undeniability property. (2) The signer is a quantum partner, while both the signature receiver and the arbitrator are classical partners. (3) The signer needn’t share any private key with the receiver. (4) The scheme is based on Bell state, which is relatively easier to be prepared than the other entanglement resources used in the similar schemes. (5) It has better qubit efficiency. Therefore, our scheme has better performances in security, practicability and efficiency than the similar schemes.
Based on the quantum asymmetric encryption with trapdoor information, a quantum public-key signature scheme is proposed. In our scheme, the signer signs a message with his/her private key, while the ...verifier verifies the quantum signature with the corresponding quantum public key. The signer’s private key and public key are asymmetric, and the signing algorithm and verifying algorithm are asymmetric as well. The security of the private key depends on the unconditionally secure deterministic quantum communication protocol rather than the classical one-way function. All the algorithms in our scheme are public. Hence, our scheme obeys Kerckhoffs’s principle. Our scheme is secure against forgery, repudiation, and eavesdropping attacks. On the other hand, in our scheme, the verifier need not perform any quantum swap test. The signer’s key pair can be reused due to the secrecy property of the private key. Compared with similar schemes, ours is relatively more secure and efficient.
This letter proposes and experimentally demonstrates a novel physical layer security method based on a piecewise chaotic permutation for orthogonal frequency division multiplexing (OFDM) passive ...optical networks. The piecewise parabolic chaotic map is adopted to generate chaotic permutation vectors, which enhance the physical layer security with a simple structure. An experiment with a 26.33-Gb/s encrypted optical OFDM signal is performed to demonstrate the proposed method. The results show good resistance against illegal optical network units and indicate that our method has the potential for use in secure optical access networks.
The traditional fast Fourier transform based frequency offset estimation (FFT-FOE) estimates the frequency offset by searching the spectral peak of the signal after the fourth power operation, which ...is suitable for multiple modulation formats. But the accuracy of FOE is limited by the number of FFT points. In this paper, we propose a high accuracy and low complexity FOE algorithm based on all phase FFT (APFFT-FOE). The accuracy of FOE can be improved effectively with lower additional computational complexity. Simulation results show that the mean square error of APFFT-FOE is reduced by more than one order of magnitude compared with the FFT-FOE. Compared with other FOE algorithms that can achieve the same accuracy, the additional computational complexity required by APFFT-FOE is reduced by more than 50<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula>. Finally, the APFFT-FOE is experimentally verified with 20 GBaud 16/64-QAM modulation signal. The experimental results show that the required OSNR for 16-QAM signal to reach 6.7<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula> hard-decision forward-error correction is relaxed by 0.23 dB. For 64-QAM signal, the required OSNR at 20<inline-formula><tex-math notation="LaTeX">\%</tex-math></inline-formula> soft-decision forward-error correction threshold is relaxed by 0.68 dB.
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