Digital contracts are formal agreements created, signed, stored, verified and executed through digital platforms. These contracts require long-term protection because they often contain legally, financially and organisationally sensitive information. However, classical cryptographic methods used in current digital contract systems may become vulnerable with advances in quantum computing. This paper focuses on Quantum Internet of Contracts (QIoCs) as a future direction for preparing digital contracts for the quantum era. It examines post-quantum cryptography, quantum communication, blockchain, smart contracts, digital identity, zero-knowledge proofs and risk-based migration strategies. The paper argues that QIoCs cannot rely on a single security method. Instead, they require a layered approach that combines quantum-resistant blockchain protocols, privacy-preserving data authentication, secure audit trails, legal governance and staged migration from classical systems to quantum-safe contract infrastructures. The paper highlights the need for legal acceptance, governance standards and real-world testing of proposed post-quantum models. Overall, the paper provides a review-based framework for building safer and more reliable digital contracts in a quantum-safe future.
Digital contracts are formal agreements created, signed, stored, verified and executed through digital platforms. These contracts require long-term protection because they often contain legally, financially and organisationally sensitive information. However, classical cryptographic methods used in current digital contract systems may become vulnerable with advances in quantum computing. This paper focuses on Quantum Internet of Contracts (QIoCs) as a future direction for preparing digital contracts for the quantum era. It examines post-quantum cryptography, quantum communication, blockchain, smart contracts, digital identity, zero-knowledge proofs and risk-based migration strategies. The paper argues that QIoCs cannot rely on a single security method. Instead, they require a layered approach that combines quantum-resistant blockchain protocols, privacy-preserving data authentication, secure audit trails, legal governance and staged migration from classical systems to quantum-safe contract infrastructures. The paper highlights the need for legal acceptance, governance standards and real-world testing of proposed post-quantum models. Overall, the paper provides a review-based framework for building safer and more reliable digital contracts in a quantum-safe future.
Blockchain ecosystems and platforms form a critical foundation for national digital economies worldwide. However, recent advancements in quantum computing, exemplified by breakthroughs from IBM and other leading developers, reveal that these systems may no longer guarantee stability and security against emerging quantum-enabled attacks. The increasing feasibility of such threats, commonly referred to as the “quantum threat,” poses unprecedented risks to the integrity, confidentiality, and reliability of blockchain infrastructures. In response, several technologically advanced countries have initiated efforts to anticipate and mitigate potential quantum cyberattacks. Ensuring the quantum resilience of blockchain systems necessitates novel approaches beyond conventional information security methods. Unlike traditional protections, these approaches aim to prevent systemic failures even under quantum-enabled adversarial conditions. The study identifies and systematizes the main directions for achieving quantum resilience, including post-quantum cryptographic primitives, modified quantum algorithms, and hybrid quantum–classical security models. The review highlights how progress in superconducting, ionic, photonic, and neutral-atom quantum platforms reshapes the threat landscape. A distinctive contribution of this work lies in its integrative perspective — linking cryptographic, architectural, and ecosystem-level aspects of blockchain sustainability under quantum threats. The proposed framework emphasizes combining post-quantum cryptography, quantum-safe protocols, and cross-domain coordination between quantum computing and cybersecurity research. Given the rapidly advancing nature of quantum technologies, the findings presented here not only reflect the current state of the field but also outline strategic directions for developing adaptive, quantum-resilient blockchain systems, including dynamic algorithmic frameworks, formal verification of quantum-resistant smart contracts, and simulation of blockchain protocols against quantum adversary models.
The rise of quantum computing poses significant threats to the cryptographic underpinnings of blockchain technologies, particularly smart contracts, which automate and secure decentralised agreements. This study investigates these quantum vulnerabilities, focusing on the potential of algorithms like Shor's to compromise widely used cryptographic systems such as ECDSA, and evaluates emerging post-quantum solutions, including lattice-based cryptography and Quantum Key Distribution (QKD), to ensure smart contract resilience. Through theoretical analysis and simulations, we demonstrate that over 98% of current smart contracts could be vulnerable to quantum attacks within the next decade, while quantum-resistant protocols offer viable countermeasures despite performance trade-offs. By integrating quantum enhancements and synthesising recent advancements in Web 3.0 and IoT contexts, this review not only highlights the urgency of transitioning to quantum-secure frameworks but also charts a path for future research to maintain the integrity and efficiency of blockchain ecosystems in the quantum era.
Web 3.0 pursues the establishment of decentralized ecosystems through blockchain technologies, driving digital transformation in commerce and governance. With consensus algorithms and smart contracts grounded in cryptographic technologies, Web 3.0 enables secure and transparent digital services, such as digital identity, asset management, decentralized autonomous organizations (DAOs), and decentralized finance (DeFi), fostering integration between digital and physical economies. As quantum devices rapidly advance, Web 3.0 is being developed in parallel with the deployment of quantum cloud computing and quantum Internet. In this regard, quantum computing first disrupts the original cryptographic systems that protect data security while reshaping modern cryptography with enhanced quantum computing and communication capabilities. This article provides a comprehensive overview of blockchain-based Web 3.0, examining its quantum and postquantum advancements from two key perspectives. On the one hand, postquantum migration methods and quantum-resistant signatures offer robust solutions to safeguard blockchain against quantum threats. On the other hand, quantum and postquantum encryption and verification algorithms boost blockchain performance, creating a decentralized, secure, and value-driven system. Additionally, we outline potential applications of quantum blockchain and offer guidance for implementation within the Web 3.0 ecosystem. Finally, we discuss future directions for developing a provably secure and decentralized digital ecosystem.
Web 3.0 pursues the establishment of decentralized ecosystems based on blockchain technologies to drive the digital transformation of physical commerce and governance. Through consensus algorithms and smart contracts in blockchain, which are based on cryptography technologies, digital identity, digital asset management, decentralized autonomous organization, and decentralized finance are realized for secure and transparent digital economy services in Web 3.0 for promoting the integration of digital and physical economies. With the rapid realization of quantum devices, Web 3.0 is being developed in parallel with the deployment of quantum cloud computing and quantum Internet. In this regard, quantum computing first disrupts the original cryptographic systems that protect data security while reshaping modern cryptography with the advantages of quantum computing and communication. Therefore, this survey provides a comprehensive overview of blockchain-based Web 3.0 and its quantum and post-quantum enhancement from the ambilateral perspective. On the one hand, some post-quantum migration methods, and anti-quantum signatures offer potential ways to achieve unforgeable security under quantum attack for the internal technologies of blockchain. On the other hand, some quantum/post-quantum encryption and verification algorithms improve the external performance of the blockchain, enabling a decentralized, valuable, secure blockchain system. Finally, we discuss the future directions toward developing a provable secure decentralized digital ecosystem.
The threats are existential to the traditional cryptosystems of public keys, including RSA, Diffie-Hellman, and elliptic curve cryptography (ECC), due to the rapid progress in quantum computing. Such algorithms as the Shor and Grover algorithms prove that as soon as large scale quantum computers are achieved, these classical cryptographic protocols will not provide any privacy and integrity to online communication. This has created an emergency to find post-quantum cryptography (PQC), or quantum-safe cryptography, which will resist attacks by both classical and quantum attackers. The paper is a review of the latest research and development in post-quantum cryptographic algorithms and their implementation in current security systems. We organize quantum-safe methods into significant organizations such as lattice-based, hash-based, multivariate polynomial-based and code-based encrypted communications. Each type has been evaluated critically based on computational efficiency, key sizes, speed of encryption/decryption and security proofs. The survey also examines the current standardization activities happening in the world and especially the U.S. National Institute of Standards and Technology (NIST) PQC competition, which lists candidate algorithms that have advanced to standard adoption. Besides this, the paper addresses hybrid cryptographic designs that use both classical and post-quantum bases in ensuring a seamless migration in the transition phase. Internet security protocols like TLS, VPNs and blockchain consensus as applications of PQC are examined in detail. Lastly, we pinpoint open research issues, which include creating lightweight PQC to support resource-constrained IoT devices, balancing performance and strong security assurances, and interoperability between the new PQC algorithms and existing infrastructures. Through detailed survey we inform the future of researchers, practitioners, and policymakers on the preparation of the post-quantum era of secure digital communications.
Quantum computing's development poses a significant threat to the cryptographic security of current blockchain technologies, potentially undermining the integrity of digital transactions. Quantum computers can break the complex mathematical problems that algorithms like RSA and ECC rely on, which could lead to vulnerabilities such as double-spending and fraud. To address these risks, the blockchain community is exploring quantum-resistant protocols that employ post-quantum cryptographic algorithms, which are designed to withstand quantum computing attacks. Quantum-secure blockchain protocols integrate quantum key distribution (QKD) and post-quantum cryptography (PQC) to enhance security. QKD uses quantum mechanics principles to secure communication channels, ensuring that any attempt to intercept the key introduces detectable anomalies. PQC involves algorithms like lattice-based, hash-based, or multivariate polynomial-based algorithms that are believed to be secure against quantum attacks. These protocols aim to maintain the confidentiality, integrity, and security of data transmitted over the blockchain, ensuring the longevity and reliability of blockchain systems in the face of evolving computational advancements. A quantum-secure blockchain scheme (QSB) utilizes a consensus mechanism, QPoA, and IQS. The QPoA is leveraged for block generation while the IQS is deployed in transaction verification1. Furthermore, the integration of quantum computing with blockchain can address current limitations, such as slow transaction speeds and lack of scalability, by optimizing calculations and enabling smarter, more sophisticated smart contracts. The development and implementation of quantum-resistant blockchains are essential for future-proofing digital transactions and maintaining trust in decentralized systems