Development of authentication code based on spectral amplitude coding optical code division multiplexing for multi-user pseudo quantum key distribution
Quantum Key Distribution (QKD) has remained the provable technique of ensuring secure communication amidst the impending security threat by the emerging quantum computers. Its security guarantee is based on superposition and entanglement, which are fundamental principle of quantum mechanics. As efforts are currently underway toward actualization of QKD network, researchers have explored a number of techniques though which this could be achieved. Some of the techniques proposed are; subcarrier based QKD network, Orthogonal Frequency Division Multiplexed (OFDM) based QKD network and spectral amplitude coding optical code division multiplexed (SAC-OCDMA) based QKD network. Among the aforementioned technique, SAC-OCDMA based system has history of efficient channel management, asynchronous nature, as well as channel security. Nevertheless, the adopted Optical Orthogonal Code (OOC) which is a family of OCDMA code, has a couple of challenges which include complex architecture, as well as longer code length, both of which are capable of resulting to reduction in the secure key rate and number of simultaneous users. Thus, this work presents a new one-weight authentication code, which are assigned, uniquely to individual user in SAC-OCDMA based QKD network. The performance of the code was explored in QKD network using simulation, mathematics and laboratory experiment. Firstly, the proof of concept of plug and play (p&p) in QKD network was carried out and the concept of phase reorientation was clearly established using Optisystem simulation tool. This was followed by mathematical modelling of the secure key rate and QBER for different number of users. As observed in the obtained results, at an average mean photon number of 0.48, a 21-user network was achieved at a secure key rate of 24 bps over a distance of 5 km. The result of comparison of the proposed code with a Wavelength Division Multiplexed (WDM) system shows its security capability above the later. The code was further compared with an OOC based network and found to generate key at higher rate when the number of users is below 14. A two-user experimental result shows the real life realization of the proposed system as a transmission distance up to 40 km was achieved with secure key rate of 320 bps. Application of the proposed code in Differential Phase Shift Key – Quantum Key Distribution (DPS-QKD) environment was also established. The obtained results have shown that aside presenting a secure mechanism, the design flexibility and moderate code length exhibited by the proposed code are excellent factors that could be explored in enhancing the performance of QKD network.
Quantum Key Distribution (QKD) has remained the provable technique of ensuring secure communication amidst the impending security threat by the emerging quantum computers. Its security guarantee is based on superposition and entanglement, which are fundamental principle of quantum mechanics. As efforts are currently underway toward actualization of QKD network, researchers have explored a number of techniques though which this could be achieved. Some of the techniques proposed are; subcarrier based QKD network, Orthogonal Frequency Division Multiplexed (OFDM) based QKD network and spectral amplitude coding optical code division multiplexed (SAC-OCDMA) based QKD network. Among the aforementioned technique, SAC-OCDMA based system has history of efficient channel management, asynchronous nature, as well as channel security. Nevertheless, the adopted Optical Orthogonal Code (OOC) which is a family of OCDMA code, has a couple of challenges which include complex architecture, as well as longer code length, both of which are capable of resulting to reduction in the secure key rate and number of simultaneous users. Thus, this work presents a new one-weight authentication code, which are assigned, uniquely to individual user in SAC-OCDMA based QKD network. The performance of the code was explored in QKD network using simulation, mathematics and laboratory experiment. Firstly, the proof of concept of plug and play (p&p) in QKD network was carried out and the concept of phase reorientation was clearly established using Optisystem simulation tool. This was followed by mathematical modelling of the secure key rate and QBER for different number of users. As observed in the obtained results, at an average mean photon number of 0.48, a 21-user network was achieved at a secure key rate of 24 bps over a distance of 5 km. The result of comparison of the proposed code with a Wavelength Division Multiplexed (WDM) system shows its security capability above the later. The code was further compared with an OOC based network and found to generate key at higher rate when the number of users is below 14. A two-user experimental result shows the real life realization of the proposed system as a transmission distance up to 40 km was achieved with secure key rate of 320 bps. Application of the proposed code in Differential Phase Shift Key – Quantum Key Distribution (DPS-QKD) environment was also established. The obtained results have shown that aside presenting a secure mechanism, the design flexibility and moderate code length exhibited by the proposed code are excellent factors that could be explored in enhancing the performance of QKD network.
This study presents the design and analysis of a hybrid multi-user quantum key distribution (QKD) system utilizing spectral amplitude coding optical code division multiple access (SAC-OCDMA) encoding techniques. By assigning unique optical codes to each user, SAC-OCDMA enables spontaneous, asynchronous data transmission without any strict synchronization, which makes it scalable and flexible for quantum networks. In the architecture, each user’s quantum signal, initially prepared as weak coherent pulses and encoded using phase or polarization bases, is further spectrally sliced by a SAC-OCDMA encoder in a zero-based cross-correlation code. The physical impairments, comprising spontaneous Raman scattering, four-wave mixing, and crosstalk, were modeled and analyzed. We report a maximum secret key rate of ∼10 5 bps over a transmission distance of ∼58km . Furthermore, our analysis demonstrates that careful selection of launch power, simultaneous users, code weight, and spectral bin width is necessary for optimizing the trade-off between multi-user capacity and security performance. In comparison with wave division multiplexing QKD, which has much better spectral efficiency but strict channel allocation, the flexibility and asynchronous access to secure communication of our OCDMA-QKD design with zero cross-correlation coding are more aligned with the needs of quantum security.
Background: Quantum Key Distribution (QKD( is a promising technology for secure communication, leveraging the principles of quantum mechanics to provide theoretically unbreakable encryption. With the exponential growth in data traffic and the increasing need for secure communication in backbone fiber networks, integrating high-bit-rate multiplexing techniques into QKD systems can enhance their efficiency and scalability. Problem: Traditional QKD systems face limitations in terms of data rate and network scalability, particularly in high-capacity optical communication networks. As data demands increase, there is a critical need for methods that can support high-bit-rate multiplexing while maintaining the security and performance of QKD. Method: This study proposes a novel QKD approach using high-bit-rate multiplexing in backbone fiber networks. The method involves encoding quantum keys using multiple optical channels simultaneously to increase the data throughput of the QKD system. We employ a combination of time-division multiplexing (TDM( and wavelength-division multiplexing (WDM( to optimize the use of fiber resources and enhance key distribution rates. Results: Simulation results demonstrate that the proposed method achieves a key distribution rate of 10 Mbps over a 200 km fiber link with a quantum bit error rate (QBER( of 1.5%. This represents a 50% improvement in key rate compared to conventional QKD systems without multiplexing. Additionally, the method shows enhanced scalability and network utilization, supporting up to 16 multiplexed channels with minimal impact on security.
Spectral Amplitude Coding Optical Code Division Multiple Access (SAC OCDMA) is an advanced technique in asynchronous environments. This paper proposes design and implementation of a novel quantum logic gate (QLG) code, with code construction algorithm generated without following any code mapping procedures for SAC system. The proposed code has a unitary matrices property with maximum overlap of one chip for various clients and no overlaps in spectra for the rest of the subscribers. Results indicate that a single algorithm produces the same length increment for codes with weight greater than two and follows the same signal to noise ratio (SNR) and bit error rate (BER) calculations for a higher number of users. This paper further examines the performance of a QLG code based SAC-OCDMA system with NAND and direct detection techniques. BER analysis was carried out for the proposed code and results were compared with existing MDW, RD and GMP codes. We demonstrate that the QLG code based system performs better in terms of cardinality, which is followed by improved BER. Numerical analysis reveals that for error free transmission (10−9), the suggested code supports approximately 170 users with code weight 4. Our results also conclude that the proposed code provides improvement in the code construction, cross-correlation and minimization of noises.
Quantum Cryptography (QC) is the emerging field of the current world and the potential player of the future. Quantum Key Distribution (QKD) is the matured discipline of QC and available in the market to establish a secret key between parties. In order to achieve in multiparty, basically quantum entanglement has been applied over a theoretical settings. However, due to practical limitation, entanglement based research has a feasible difficulty with current technology. The thesis principal goal is to propose a framework for quantum protocol layer for secure key management without entanglement over multiparty environment. In the secret key management, conference key or Multiparty QKD (MQKD) and joint-venture key or Public Shared Secret Quantum Key (PSSQK) protocols acted as a top layer and quantum user authentication scheme as a middle layer and the standard QKD operation as a bottom layer. The proposed secrete key management protocols are based on secret key between parties using QKD, modified error correction code and linear independent matrix. These protocols require only classical communication and yield higher secret key rate regardless of distance and noise. The security analysis using guessing entropy has applied and results shows only negligible amount information can be extracted during eavesdropping. The challenge-challenge response technique has been applied to proposed quantum user authentication scheme for verification of quantum user. This is a bidirectional authentication scheme and requires both quantum and classical channel to execute and has two modes of operation, i.e., initial and session authentication.Due to deterministic key distribution orientation, the efficiency of protocol reaches up to 100% in terms of reduction of photon wastage during communication. Further, this scheme is resilient to various quantum security attacks However, this scheme requires noiseless quantum channel in order to detect the insider and outsider attacks during authentication. A GUI based discrete event simulation has developed using OptiSystem™ in order to test the practical feasibility of proposed quantum cryptography protocol layer. The polarized based discrete variable QKD protocols have been designed and analyzed. Due to lack of real receiver setup, the results have showed lower quantum bit error rate. Further, we analyzed the impact of polarization structure of qubit due to noise, loss and distance over fiber optics and free space. A multiparty QKD setuphas been designed based on frequency division multiplexing (FDM) centralized quantum channel server. This approach reduces the requirement of total quantum channel from N*(N-1)/2 to N and each party requires one quantum channel to communicate with all other parties. The bit commitment protocol and message authentication in the layer has considered for the future research direction.
With the rapid development of high-security applications such as finance, cloud computing, and key government services, network security issues have become increasingly prominent. Against this backdrop, quantum key distribution (QKD) technology has emerged as an important solution to address the security challenges of optical networks. Based on the principles of quantum mechanics, this technology can achieve unbreakable key distribution during communication, providing intrinsic security for the exchange of confidential information. It is currently one of the most promising long-term security protection technologies for optical networks.Due to the high cost of independently deploying quantum communication networks, integrating quantum channels with classical optical networks for transmission has become the most feasible solution at present. Meanwhile, the continuous development of technologies such as high-order modulation and wavelength division multiplexing has brought the transmission capacity of conventional single-mode fibers close to their theoretical Shannon limit, and mode division multiplexing(MDM) can effectively solve the problem of transmission capacity.However, quantum signals are highly susceptible to crosstalk caused by classical signals during the simultaneous transmission with classical signals. This paper conducts a simulation experiment on a quantum-classical fusion system based on MDM. The results show that the quantum signals are not significantly interfered with by the classical signals during simultaneous transmission, and this system is suitable as a simultaneous transmission scheme for large-scale networking of quantum secure communication.
Quantum Key Distribution (QKD) is currently receiving much attention as it provides a secure source of encryption keys. Discrete-Variable QKD (DV-QKD) is possible for single photon transmission in QKD to-coexist with and encode classical wavelength division multiplexed (WDM) data with appropriate system design. Nevertheless, previous QKD field trials adopted either or both of key relay via trusted nodes and transparent link via optical switching. The former requires guaranteed physical security of the relay nodes, but can expand key distribution distance arbitrarily. The latter can realize key establishment for more users with less complexity of key management over an untrusted network. To realise the adaption of the QKD system for future high speed and long distance metropolitan world exploitation at lower cost, there has to be investigations on existing fibre infrastructures. Prior to this work, previous researches over similar distances feature extremely low secure key rates. For example, the Swiss Quantum Network between three sites displayed secure bit rates of 2.5 kbps at a fibre length of 17km. Quantum Key distribution within the 25km Cambridge Quantum Network have demonstrated the highest long-term secure key rates yet demonstrated in a field trial of at least 2.5Mb/s which is the fastest and much higher than 0.8 kbps which was reached over the similar channel loss field trial up to date. Additional field trials have been performed on the UK Quantum Network using a 66km path having 16dB loss. Combined wavelength division multiplexed 2 x 100 Gb/s traffic encrypted using QKD co-existing on the same fibres has operated for several months, with a long-term key rate of 80kb/s that is also faster than any other similar long-term QKD trial systems. In addition to this advanced commercial QKD system, there have been secure key rate analysis comparisons between laboratory fibre coils and practical field trials more than field trials only conducted before.These comparisons help to identify factors that limit future QKD network scale in both quantity and quality aspects. Also, the limit for the highest secure key rate at longest fibre length QKD in the multiplexing environment is discussed and determined in this research thesis. Nevertheless, in this thesis, improvements have been made to minimise the corresponding negative effects by investigations on the dependence of temperature have been done in order to ensure system operation environment effects. It was found from the trial results that there exists a relationship between temperature and secure key rate and further study has been done to evaluate the system sensitivity to operating temperature. Although the conventional DV-QKD system, original BB84 coding scheme, was designed to exploit the quantum properties of single photon polarization states, the trial equipment operates based upon the phase coding schemes. These coding schemes are based on the properties of interferometers and the coding is implemented by changing the relative optical path lengths or phase between the internal arms of the interferometer, while in the real transmission environment, temperature or polarization variation happens unpredictably. The existing polarisation controllers operate at relative low speed align within the interferometer, which slows to operation environment such as a punch to fibre causing phase difference. Therefore, in this project, there has been an improvement in the QKD-WDM system performance by adding an external polarization controller to minimize the Raman noise and increase the secure key rate at the longest fibre length up to date. In Summary, transmitting quantum keys over a coil of fibre in the lab differs a lot from actually putting it in the ground. This work contrasts the world fastest QKD system at the longest distance in field trials with lab fibre reels and then characterises and identifies two of the key factors, temperature and polarizations, influencing performance in practical wavelength-multiplexed secure communication systems. This is a significant step towards the coexistence of the quantum and conventional data channels on the same fibre for metropolitan networks and paves a way for an information-secure communication infrastructure.