The rapid advancement of quantum computing, exemplified by Shor’s and Grover’s algorithms, poses an existential threat to the Rivest-Shamir-Adleman algorithm, elliptic curve cryptography, and symmetric encryption. This paper presents a critical and integrative review of two defensive paradigms, quantum key distribution and post-quantum cryptography, covering studies published from 2020 to 2026 and mapped to four objectives spanning quantum threats, quantum key distribution viability, standardization, and hybrid synergies. Quantum key distribution protocols offer information-theoretically secure key distribution, though twin-field quantum key distribution’s 833.8 kilometer distance record comes at secure key rates as low as 0.014 bits per second. Post-quantum cryptography algorithms spanning lattice-based, code-based, hash-based, multivariate, and isogeny-based schemes offer unlimited range but rest on unproven mathematical assumptions, illustrated by the 2022 classical break of the Supersingular Isogeny Diffie-Hellman scheme and a 2024 quantum attack on the Rainbow signature scheme. Following the National Institute of Standards and Technology’s 2024 finalization of its primary standards, with the Hamming Quasi-Cyclic scheme subsequently added as a backup key encapsulation mechanism, this review identifies five hybrid architectural patterns combining quantum key distribution and post-quantum cryptography, evaluates their maturity from proposed to experimentally validated, and quantifies their cost: hybrid throughput collapses by two orders of magnitude once quantum key distillation is incorporated. Comparative benchmarking, an architecture diagram, and a thematic analysis identify quantum repeater networks, long-term cryptanalysis, and security-performance trade-off frameworks as critical research gaps, positioning hybrid integration as the most promising pathway toward secure communications.
The rapid advancement of quantum computing, exemplified by Shor’s and Grover’s algorithms, poses an existential threat to the Rivest-Shamir-Adleman algorithm, elliptic curve cryptography, and symmetric encryption. This paper presents a critical and integrative review of two defensive paradigms, quantum key distribution and post-quantum cryptography, covering studies published from 2020 to 2026 and mapped to four objectives spanning quantum threats, quantum key distribution viability, standardization, and hybrid synergies. Quantum key distribution protocols offer information-theoretically secure key distribution, though twin-field quantum key distribution’s 833.8 kilometer distance record comes at secure key rates as low as 0.014 bits per second. Post-quantum cryptography algorithms spanning lattice-based, code-based, hash-based, multivariate, and isogeny-based schemes offer unlimited range but rest on unproven mathematical assumptions, illustrated by the 2022 classical break of the Supersingular Isogeny Diffie-Hellman scheme and a 2024 quantum attack on the Rainbow signature scheme. Following the National Institute of Standards and Technology’s 2024 finalization of its primary standards, with the Hamming Quasi-Cyclic scheme subsequently added as a backup key encapsulation mechanism, this review identifies five hybrid architectural patterns combining quantum key distribution and post-quantum cryptography, evaluates their maturity from proposed to experimentally validated, and quantifies their cost: hybrid throughput collapses by two orders of magnitude once quantum key distillation is incorporated. Comparative benchmarking, an architecture diagram, and a thematic analysis identify quantum repeater networks, long-term cryptanalysis, and security-performance trade-off frameworks as critical research gaps, positioning hybrid integration as the most promising pathway toward secure communications.
The rapid growth of quantum computing poses a critical threat to classical cryptographic systems. That is due in large part to the fact that they represent efficient solutions for some of the most challenging mathematical problems such as integer factoring or finding discrete logarithms. Schemes currently in wide use including RSA, Diffie–Hellman, and elliptic curve cryptography are particularly susceptible to being attacked by quantum computers, using algorithms like Shor's Algorithm and Grover's Algorithm. The advent of post-quantum cryptography (PQC) provides a promising potential answer to providing longterm security from adversaries using quantum computing capabilities. This paper presents a comprehensive state-of-the-art review of various PQC techniques currently being researched, including lattice-based methods, code-based methods, multivariate methods, hash-based methods, and isogeny-based methods. key challenges that will need to be addressed include computational overhead, large key sizes and implementation complexity. Furthermore the study reviews the current standardization efforts by the National Institute of Standards and Technology related to PQC and discusses some of the very specific practical considerations that need to be considered before widely deploying these techniques. The paper concludes by a complete list of existing research challenges and proposed future work that will assist in the development of efficient and scalable systems that will resist attacks from quantum computers.
Quantum computing advances pose a serious threat to conventional public-key cryptographic systems such as RSA and elliptic curve cryptography as quantum algorithms may undermine the computational assumptions that guaranty their security. This challenge has driven the development of quantumsafe security approaches among which Quantum Key Distribution (QKD) represents a fundamentally different paradigm based on quantum mechanical principles rather than mathematical complexity. This paper presents a structured review of recent progress in QKD based on a systematic analysis of literature between 2020 and 2025, we examine core protocols including discrete-variable, continuous-variable, measurement-deviceindependent, and twin-field approaches, while also discussing their relationship with post-quantum cryptography as a complementary strategy for future secure communication systems. We provide a unified comparison framework to support practical design and policy decisions by organizing protocols and implementations along deployment dimensions. The study analyze theoretical foundations, implementation technologies across fiber, free-space, satellite, and integrated photonic platforms, and key performance trade-offs involving scalability, security robustness, and deployment feasibility. Findings indicate substantial progress in transitioning QKD from laboratory research toward practical implementations, supported by advances in network architectures, integrated hardware and hybrid cryptographic designs. The comparative analysis will highlight distinct strengths and limitations among protocol families and emphasize the potential of combining QKD with post-quantum cryptographic methods to enhance resilience. Remaining challenges including scalability constraints, implementation-level vulnerabilities, performance limitations over long distances, and integration with existing communication infrastructures are critically discussed. Finally, emerging research directions such as quantum repeaters, hybrid quantum-classical security models, and exploratory directions such as artificial intelligence-assisted optimizations are identified as key factors in enabling the evolution of QKD toward largescale quantum-secure networking.
The advent of quantum computing poses a significant challenge to conventional cryptographic methods such as RSA, Elliptic Curve Cryptography (ECC), and Diffie-Hellman key exchange. Quantum algorithms, particularly Shor’s algorithm, have the potential to break these encryption techniques, making it essential to develop cryptographic approaches that can withstand quantum threats. Post-quantum cryptography (PQC) has emerged as a crucial area of research, aiming to establish cryptographic mechanisms that remain secure even in the presence of quantum adversaries. This study presents a detailed comparative analysis of five primary categories of quantum-resistant cryptographic algorithms: lattice-based, code-based, hash-based, multivariate polynomial, and isogeny-based encryption schemes. Each of these approaches offers distinct advantages and challenges in terms of security, efficiency, and implementation feasibility. Among them, lattice-based cryptography has gained significant attention due to its robust security properties and computational efficiency, making it a strong candidate for standardization. Conversely, code-based cryptography provides high security but is hindered by its large key sizes, affecting its practical deployment. The research includes a real-time performance assessment of selected PQC algorithms, analyzing key factors such as encryption speed, key size, and computational demands. Furthermore, the study examines the challenges associated with transitioning from classical encryption standards to quantum-resistant frameworks, including compatibility constraints, computational overhead, and the necessity for global standardization. Potential mitigation approaches, such as hybrid cryptographic techniques that integrate both classical and post-quantum encryption models, are also explored. Our findings emphasize that while quantum-resistant cryptography is still evolving, early adoption of PQC frameworks is essential for safeguarding future communication networks. This paper provides valuable insights for researchers, cybersecurity professionals, and policymakers on strategic measures to implement quantum-secure encryption systems effectively.
As quantum computing advances toward practical use, classical cryptography is at a serious risk of being compromised, especially with the use of quantum algorithms like the Shor algorithm, which can break RSA in polynomial time, as well as Elliptic Curve Cryptography (ECC). This research paper highlights the urgent need to protect electronic communications against quantum attacks by leveraging two novel approaches: Quantum Key Distribution (QKD) and Post-Quantum Cryptography (PQC). The study aims to evaluate the effectiveness, scalability, and integration possibility of these technologies separately and in mixed combinations, to achieve long-term resilient cybersecurity. This research is a mixed-methods study that combines literature analysis, expert surveys, and performance benchmarking to determine the strength of encryption, compatibility with the network, and feasibility in the real world. First-hand information was gathered through structured surveys among cybersecurity professionals and scholars. In contrast, second-hand information was retrieved from peer-reviewed journals and official standards of institutions, such as NIST. It has been found that QKD offers unparalleled information-theoretic security, founded on quantum mechanics, yet has limitations in terms of scale and cost. PQC algorithms, however, especially lattice-based cryptography, are simpler to integrate into a classical infrastructure but present a performance issue on hardware with limited capabilities. Based on the study, a hybridized cryptographic model appears to be the best solution to the current approach of implementing the secure key exchange properties of QKD and the universal properties of PQC, without compromising either.
Classical cryptography faces significant challenges from quantum computing, particularly due to the power of Shor’s and Grover’s algorithms, which threaten widely used encryption methods. This study examines a range of post-quantum cryptography (PQC) schemes designed to withstand quantum attacks, including lattice-based, isogeny-based, hash-based, code-based, and multivariate approaches. It also explores Quantum Key Distribution (QKD) protocols, highlighting both prepare-and-measure and entanglement-based techniques. A detailed comparison of PQC algorithms is presented, evaluating their security, efficiency, and practicality for implementation. The findings offer strategies to future-proof digital communications against quantum threats, while addressing the key challenges quantum computing introduces to cryptographic systems.
This preprint presents a systematic review of how quantum computing impacts the security of classical cryptography and what mitigation strategies are available. The review synthesises key survey papers, standards reports and transition guidelines on post-quantum cryptography (PQC) and quantum-safe security published between 2015 and 2025. First, the paper summarises the impact of Shor’s and Grover’s algorithms on widely deployed public-key schemes, symmetric ciphers and hash functions, highlighting in particular the existential break of RSA, Diffie–Hellman and elliptic-curve cryptography, and the reduced security margins for symmetric and hash-based constructions. It then examines major quantum-resilient responses, including lattice-, code-, multivariate- and hash-based PQC, quantum key distribution (QKD), hybrid classical–PQC schemes and crypto-agile architectures. Building on Mosca’s x, y, z risk-timing model, the review discusses cross-cutting themes such as harvest-now-decrypt-later threats and sector-specific implications for government and defence, finance and blockchain, healthcare, cloud providers and critical infrastructure. It identifies several research gaps, including the lack of quantitative migration-cost data, limited coverage of small and resource-constrained organisations, and few system-scale evaluations comparing PQC-only, hybrid and QKD-based designs. The paper concludes by arguing that planning and investment in quantum-resilient cryptography need to start now, before migration time and data shelf-life push critical systems into the risky regime.