Quantum computers pose a long-term threat to classical cryptographic systems, including those used in blockchain platforms. While prior work has estimated the number of logical qubits required to compromise cryptographic schemes such as RSA and ECDSA, relatively few studies have modeled when such quantum capacity might realistically be achieved. In this paper, we construct a time-series dataset of publicly documented gate-based quantum processors developed between 2016 and 2025. We estimate the number of logical qubits under three fault-tolerance scenarios and apply forecasting models based on exponential trend analysis. Our results provide year-by-year projections for when quantum computers may reach logical qubit thresholds associated with widely used cryptographic schemes. These projections are mapped to specific blockchain security mechanisms, offering a practical timeline for transition planning toward post-quantum systems. These projections should be interpreted as indicators of logical qubit availability rather than precise estimates of full cryptanalytic execution timelines.
Quantum computers pose a long-term threat to classical cryptographic systems, including those used in blockchain platforms. While prior work has estimated the number of logical qubits required to compromise cryptographic schemes such as RSA and ECDSA, relatively few studies have modeled when such quantum capacity might realistically be achieved. In this paper, we construct a time-series dataset of publicly documented gate-based quantum processors developed between 2016 and 2025. We estimate the number of logical qubits under three fault-tolerance scenarios and apply forecasting models based on exponential trend analysis. Our results provide year-by-year projections for when quantum computers may reach logical qubit thresholds associated with widely used cryptographic schemes. These projections are mapped to specific blockchain security mechanisms, offering a practical timeline for transition planning toward post-quantum systems. These projections should be interpreted as indicators of logical qubit availability rather than precise estimates of full cryptanalytic execution timelines.
We consider how to forecast progress in the domain of quantum computing. For this purpose we collect a dataset of quantum computer systems to date, scored on their physical qubits and gate error rate, and we define an index combining both metrics, the generalized logical qubit. We study the relationship between physical qubits and gate error rate, and tentatively conclude that they are positively correlated (albeit with some room for doubt), indicating a frontier of development that trades-off between them. We also apply a log-linear regression on the metrics to provide a tentative upper bound on how much progress can be expected over time. Within the (generally optimistic) assumptions of our model, including the key assumption that exponential progress in qubit count and gate fidelity will continue, we estimate that that proof-of-concept fault-tolerant computation based on superconductor technology is unlikely (<5% confidence) to be exhibited before 2026, and that quantum devices capable of factoring RSA-2048 are unlikely (<5% confidence) to exist before 2039. It is of course possible that these milestones will in fact be reached earlier, but that this would require faster progress than has yet been seen.
The maturation of quantum computing hardware and algorithms has transformed what was once a theoretical concern into an active planning priority for governments, enterprises, and standards bodies. This paper assesses the current and projected threat that quantum computation poses to classical public-key cryptographic standards, namely RSA, elliptic curve cryptography (ECC), and Diffie-Hellman key exchange, all of which derive their security from mathematical problems that Shor's algorithm renders tractable on a sufficiently large fault-tolerant quantum computer. We synthesize recent hardware progress, algorithmic refinements that have substantially reduced estimated qubit requirements, and the finalization of NIST's post-quantum cryptography (PQC) standards (FIPS 203, 204, and 205) to provide an evidence-based assessment of where the field stands as of mid-2026. Particular attention is given to the widening gap between optimistic resource estimates, including a contested March 2026 claim of a thousand-fold reduction in factoring resources, and the practical reality that no existing quantum computer approaches the logical qubit counts required to threaten deployed encryption. We further examine migration challenges, including performance overhead, cryptographic agility, constraints on embedded and IoT systems, and the harvest-now-decrypt-later threat model that makes migration urgency independent of exact timeline predictions. Drawing on NIST transition guidance and recent G7 coordination targets, we argue that organizations should treat cryptographic migration as a present-tense operational requirement rather than a future contingency, regardless of unresolved disagreement among experts about when a cryptographically relevant quantum computer will exist. The paper concludes with practical recommendations for risk-based migration prioritization and identifies open research questions in cryptographic agility and quantum-resistant system design.
Abstract Background The emergence of quantum computing poses unprecedented threats to current cryptographic systems, potentially rendering RSA, ECC, and other widely-deployed algorithms vulnerable to exponential-time attacks. Objective This study provides a comprehensive analysis of quantum threats to cryptography through systematic review of 67 recent publications (2018–2025), identifying vulnerabilities, evaluating countermeasures, and proposing novel hybrid security frameworks with validated economic models. Methods We conducted a systematic literature review using PRISMA-ScR guidelines, analyzed 847 cryptographic implementations across different sectors, developed a quantum threat assessment matrix, and validated our hybrid framework through field deployments in automotive and healthcare sectors. Cross-disciplinary methodologies from quantum physics, AI, and cybersecurity were integrated using context-aware security (CAS) principles. Results Our analysis reveals three critical threat vectors: immediate harvest-now-decrypt-later (HNDL) attacks affecting 67% of surveyed organizations, medium-term RSA/ECC vulnerabilities projected for 2030–2035, and long-term post-quantum transition challenges. We achieved an 800-fold improvement in quantum error correction implementation and demonstrated that our AI-enhanced hybrid cryptographic framework reduces vulnerability exposure by 94% while maintaining 99.4% system uptime. Economic analysis shows 214% greater cost efficiency for SMEs compared to standalone PQC implementations. Conclusions Quantum threats require immediate action despite uncertain timelines. Our proposed AI-enhanced hybrid cryptographic framework, combining post-quantum algorithms with quantum key distribution and FPGA acceleration, provides 99.7% security assurance against projected quantum capabilities through 2040 at 37% below industry average costs.
Introduction The rapid advancement of quantum computing presents an existential threat to the mathematical foundations of modern internet security. Fault-tolerant quantum computers are projected to reach the logical qubit scale necessary to execute Shor's algorithm by 2030–2035, threatening currently deployed public-key cryptography infrastructures. Methods We evaluate the performance metrics of integrating post-quantum cryptography (PQC), specifically the newly finalized NIST standards (FIPS 203, 204, and 205), with quantum key distribution (QKD) across communication networks. Results Our analysis demonstrates that while hybrid PQC-QKD models reduce long-term key compromise probabilities to near 0%, they introduce a 15% to 40% increase in bandwidth overhead during initial cryptographic handshakes. Discussion Given that enterprise-wide cryptographic migrations historically require 7–10 years, organizations face an immediate vulnerability window against “harvest now, decrypt later” adversaries. Ultimately, we propose a phased, cryptographically agile framework to achieve a Zero-Trust, Quantum-Safe network architecture within a 5-year implementation timeline.
The advent of quantum computing has generated apprehensions regarding the viability and security of conventional cryptographic algorithms. These algorithms safeguard the decentralized trust built into the blockchain, which relies on decentralized cryptographic consensus, instead of a central authority. Simultaneously, quantum computing has also unveiled unprecedented possibilities, opportunities and risks in the realm of technology. The significance of this is that numerous sub-routines employed within the blockchain, such as consensus protocols, data transmission, storage, and communication, heavily depend on conventional cryptographic algorithms like Rivest-Shamir-Adleman (RSA) and Elliptic Curve Digital Signature Algorithm (ECDSA). However, these algorithms are susceptible to quantum algorithms, which have the potential to effectively compromise them once quantum computers with sufficient computational capabilities are developed. Blockchain, although primarily recognized for its association with cryptocurrencies, is essentially a decentralized and trustless distributed ledger system. Its purpose is to enable decentralized communication, coordination, and the attainment of desired objectives through consensus mechanisms. A notable illustration of this concept is a blockchain transaction. The advent of quantum computing poses a significant threat to the security of blockchain systems, as the asymmetric algorithms employed within their many components will likely become obsolete. This jeopardizes the integrity of the blockchain system, which underpins a multi-billion dollar economy reliant on its inherent transparency and safety. This paper seeks to present an overview of the various threats faced by blockchain systems, examine the potential of quantum algorithms in offering cryptographic signatures for these systems, and provide a broad perspective on how to protect blockchain systems from quantum threats by utilizing quantum algorithms for cryptographic signatures. This study enhances the comprehension of existing vulnerabilities in blockchain systems, specifically focusing on the potential risks posed by quantum computing. Additionally, it sheds light on the ongoing efforts within the industry and current research endeavors aimed at addressing these weaknesses.
With the arrival of fault-tolerant quantum computers, an existential threat has come to the cryptographic underpinnings of the security infrastructure in place for modern information technologies. Virtually all secure digital communication protocols used today are based on classical public-key cryptographic systems – RSA, Elliptic Curve Cryptography (ECC) and Diffie-Hellman key exchange – that are susceptible to polynomial-time quantum attacks using Shor's algorithm. Symmetric cryptographic algorithms that are not broken are being effectively halved by Grover's algorithm, for example, AES. In this article, a complete and journal-standard systematic review of quantum computing and its implications in the field of information technology security is presented which includes 22 peer-reviewed publications from 2023-2025. The study covers the basics of quantum computing (qubits, superposition, entanglement and quantum gates), and how quantum computing specifically poses a threat to classical cryptography via algorithmic mechanisms. The three post-quantum cryptographic algorithms that were standardised by the National Institute of Standards and Technology (NIST) in August 2024 (ML-KEM, FIPS 203; ML-DSA, FIPS 204; and SLH-DSA, FIPS 205) are compared based on their security assumptions, performance, and readiness for deployment. The practical limitations and the use of Quantum Key Distribution, (QKD), as a physics based alternative to the computational security assumptions are discussed. Results show that although mature PQ solutions are now available for most cryptographic applications, the migration challenge, including legacy system transitions, migration architecture, and governance, is significant and pressing as the ‘harvest now, decrypt later’ threat model is relevant and adversaries might be collecting encrypted data for quantum decryption. The impact for financial services, health care, government, cloud infrastructure and critical national infrastructure is discussed. Lastly, the researchers list key research areas: standardisation of quantum-safe protocols, hybrid PQC-QKD designs, light-weight PQC for constrained devices, and quantum-safe blockchain.