Although quantum key distribution (QKD) provides information-theoretically secure keys, a significant gap exists between its relatively low key generation rate and the high-speed demands of classical optical communication. To address this challenge, this paper proposes a stream cipher encryption scheme based on QKD and Secure Hash Algorithm 256 (SHA-256). Core to the scheme is an innovative group-wise dual-randomized affine construction. Integrated with configurable grouping and parallel processing, this mechanism applies a linear mapping defined by dynamic initial vectors (IV) and variable full-domain strides to each data group. This approach achieves deep orthogonalization of the hash input space while preserving architectural parallelism. Simulation results demonstrate that the scheme achieves high-strength security protection while ensuring real-time performance of the communication link. Specifically, statistical analysis confirms that the ciphertext exhibits high entropy and negligible autocorrelation, alongside high key sensitivity. The scheme expands the computational search space beyond the conventional 2 256 bound, effectively countering pre-computation attacks.
Although quantum key distribution (QKD) provides information-theoretically secure keys, a significant gap exists between its relatively low key generation rate and the high-speed demands of classical optical communication. To address this challenge, this paper proposes a stream cipher encryption scheme based on QKD and Secure Hash Algorithm 256 (SHA-256). Core to the scheme is an innovative group-wise dual-randomized affine construction. Integrated with configurable grouping and parallel processing, this mechanism applies a linear mapping defined by dynamic initial vectors (IV) and variable full-domain strides to each data group. This approach achieves deep orthogonalization of the hash input space while preserving architectural parallelism. Simulation results demonstrate that the scheme achieves high-strength security protection while ensuring real-time performance of the communication link. Specifically, statistical analysis confirms that the ciphertext exhibits high entropy and negligible autocorrelation, alongside high key sensitivity. The scheme expands the computational search space beyond the conventional 2 256 bound, effectively countering pre-computation attacks.
Quantum Noise Stream Cipher (QNSC) has emerged as a physical-layer encryption technique that exploits quantum noise and non-orthogonal coherent-state modulation to secure optical communication. However, the security of QNSC relies exceedingly on the secrecy and freshness of its seed key. Quantum Key Distribution (QKD), on the other hand, provides information-theoretically secure key exchange rooted in the laws of quantum mechanics. The convergence of these two paradigms, i.e., integrated QKD-QNSC architectures, offers a compelling solution to each of their limitations. In such integrated systems, QKD continuously supplies and refreshes the secret seed key that governs QNSC modulation. Thus, governing a unified security framework that couples provably secure key establishment with high-speed quantum-enhanced physical-layer encryption. This work presents a comprehensive review of QNSC systems, examining their operating principles, security models under various attacks, and their integration with QKD systems. We analyze the security interplay between the key generation and encryption layers and survey experimental demonstrations and architectural progress toward practical deployment. Furthermore, we identify the open challenges and future research directions that must be addressed to realize fully integrated, quantum-secured optical communication networks at a practical scale.
Securing optical communication networks against evolving cyber threats necessitates advanced cryptographic techniques. Quantum cryptography offers an unbreakable security framework, leveraging the principles of quantum mechanics. However, integrating quantum cryptography with lightweight and efficient stream ciphers remains a challenge in high-speed optical networks. Traditional encryption methods, such as AES and RSA, struggle to meet the real-time demands of optical communication due to computational overhead and vulnerability to quantum attacks. This study introduces a hybrid security framework incorporating Quantum Key Distribution (QKD) with Espresso ciphers and the Grain stream cipher to enhance security and efficiency in optical networks. The Espresso cipher, known for its ultra-lightweight design and energy efficiency, ensures minimal computational complexity, while the Grain stream cipher provides robust resistance against differential and linear cryptanalysis. The integration with QKD ensures unconditional security through quantum properties such as no-cloning and Heisenberg’s uncertainty principle. Performance evaluation was conducted using a 100 Gbps optical network, demonstrating a significant reduction in encryption latency by 37% compared to conventional AES-based encryption. The proposed framework also achieved an 89.6% improvement in key generation efficiency and reduced computational overhead by 41.3%. Furthermore, resistance against brute-force and side-channel attacks was significantly enhanced, providing a secure and efficient cryptographic solution for high-speed optical networks.
Quantum secure communication technology, grounded in the principles of quantum mechanics, has revolutionized traditional cryptographic methods, which predominantly rely on mathematical algorithms and logical transformations. Quantum key distribution (QKD) facilitates the secure sharing of symmetric keys between legitimate parties, ensuring the integrity and confidentiality of information in communication channels. Among various QKD schemes, continuous variable quantum key distribution (CV-QKD) has emerged as a viable alternative to the more established discrete variable quantum key distribution (DV-QKD). CV-QKD boasts several advantages, including straightforward deployment, reduced operational costs, and stable signal quality, positioning it as a significant component of the quantum communication landscape. Quantum noise stream cipher (QNSC) represents a technique that employs redundant data streams to encrypt plaintext. Notably, QNSC shares structural similarities with the optical path used in quantum key distribution, allowing for compatibility with existing QKD infrastructure. Furthermore, the keys generated through quantum key distribution ensure absolute security, enabling them to substitute the data streams produced by pseudo-random sequences traditionally used in classical encryption schemes. This substitution enhances the overall security framework of the quantum noise stream encryption approach. The quantum access network (QAN) extends quantum key distribution capabilities from point-to-point connections to point-to-multipoint configurations, thereby becoming an essential component of contemporary network architectures. By interlinking multiple end users with a network backbone, quantum access networks can seamlessly integrate with quantum key distribution protocols. This integration offers a cost-effective and scalable solution for user access to the network. Extensive experimental verifications have demonstrated the viability of downstream access networks, indicating that the merging of quantum access network structures with quantum stream encryption technologies can yield a comprehensive quantum experimental platform. On this platform, security keys are derived through quantum key distribution, which subsequently facilitates the encryption of plaintext information. Notably, experimental validations involving eight users have been successfully executed on this platform, underscoring its practical applicability and effectiveness.
Optical communications providing huge capacity and low latency remain vulnerable to a range of attacks. In consequence, encryption at the optical layer is needed to ensure secure data transmission. In our previous work, we proposed LightPath SECurity (LPSec), a secure cryptographic solution for optical transmission that leverages stream ciphers and Diffie-Hellman (DH) key exchange for high-speed optical encryption. Still, LPSec faces limitations related to key generation and key distribution. To address these limitations, in this paper, we rely on Quantum Random Number Generators (QRNG) and Quantum Key Distribution (QKD) networks. Specifically, we focus on three meaningful scenarios: In Scenario A, the two optical transponders (Tp) involved in the optical transmission are within the security perimeter of the QKD network. In Scenario B, only one Tp is within the QKD network, so keys are retrieved from a QRNG and distributed using LPSec. Finally, Scenario C extends Scenario B by employing Post-Quantum Cryptography (PQC) by implementing a Key Encapsulation Mechanism (KEM) to secure key exchanges. The scenarios are analyzed based on their security, efficiency, and applicability, demonstrating the potential of quantum-enhanced LPSec to provide secure, low-latency encryption for current optical communications. The experimental assessment, conducted on the Madrid Quantum Infrastructure, validates the feasibility of the proposed solutions.
In the quantum noise stream cipher (QNSC) system, the low-order plaintext is encrypted by pre-shared keys into high-order ciphertext. However, high-speed optical communication systems have a huge demand for pre-shared keys. On the other hand, the separation of the secure communications sub-system from the secure key distribution (SKD) sub-system increases potential security risks and introduces additional resources overhead. In this letter, we propose an artificial amplitude noise-based SKD scheme (AAN-SKD) in QAM/QNSC to generate secret key for legal parties accordingly. The two orthogonal PAM symbols are superimposed to generate QAM symbols. Thus, the AAN-SKD can also be implemented in PAM modulation. In addition, the data transmission and AAN-SKD are completed in the same channel. Experimental results indicate that the key generation rate and key consistency ratio of the proposed scheme can reach188.22Mbit/sand 91%, respectively. Compared with quantum key distribution, the AAN-SKD has the advantage of lower cost, better compatibility, and a higher key rate.
We propose and experimentally demonstrate a compatible physical-layer secure optical communication (PLSOC) system that integrates self-adaptive physical-layer key distribution (PLKD) and encryption (PLE) in optical coherent communication. Based on bit error rate difference of QAM signals mapped by asymmetric basis state Y-00 protocol, the secret key can be secretly exchanged over public fiber links without the pre-shared keys. Moreover, we perform a parameter self-adaptive strategy for practical and dynamic PLKD. The security of the key is evaluated in the case of a fiber-tapping attack. A secure hash algorithm, SHA3-512, is used to perform privacy amplification to obtain the virtually secure key. An error-free PLKD rate reaches 39.3 Kbits/s over 300 km ultra-low loss fiber. We experimentally enable the integration of the proposed PLKD scheme and quantum noise stream cipher (QNSC) with a single wavelength, same system. Q factor penalty of the integration system compared to the QNSC system is 3.7 dB (optical back-to-back) and 4.8 dB (300 km) respectively. By exploiting a common hardware platform, with the same wavelength, the proposed PLSOC system addresses the problem that PLKD and PLE are separately performed through independent optical fiber links or wavelengths. Since only digital signal processing is used, the scheme does not require extra hardware.