Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1902.05214

Smart contracts meet quantum cryptography

Andrea Coladangelo

Published Feb 14, 2019• 10 citations
arXivHTMLPDF

Abstract

We put forward the idea that classical blockchains and smart contracts are potentially useful primitives not only for classical cryptography, but for quantum cryptography as well. Abstractly, a smart contract is a functionality that allows parties to deposit funds, and release them upon fulfillment of algorithmically checkable conditions, and can thus be employed as a formal tool to enforce monetary incentives. In this work, we give the first example of the use of smart contracts in a quantum setting. We describe a simple hybrid classical-quantum payment system whose main ingredients are a classical blockchain capable of handling stateful smart contracts, and quantum lightning, a strengthening of public-key quantum money introduced by Zhandry [Eurocrypt 2019]. Our hybrid payment system uses quantum states as banknotes and a classical blockchain to settle disputes and to keep track of the valid serial numbers. It has several desirable properties: it is decentralized, requiring no trust in any single entity; payments are as quick as quantum communication, regardless of the total number of users; when a quantum banknote is damaged or lost, the rightful owner can recover the lost value.

DOI
10.48550/arxiv.1902.05214

Related papers

A Quantum Money Solution to the Blockchain Scalability Problem

Andrea Coladangelo, Or Sattath

We put forward the idea that classical blockchains and smart contracts are potentially useful primitives not only for classical cryptography, but for quantum cryptography as well. Abstractly, a smart contract is a functionality that allows parties to deposit funds, and release them upon fulfillment of algorithmically checkable conditions, and can thus be employed as a formal tool to enforce monetary incentives. In this work, we give the first example of the use of smart contracts in a quantum setting. We describe a simple hybrid classical-quantum payment system whose main ingredients are a classical blockchain capable of handling stateful smart contracts, and quantum lightning, a strengthening of public-key quantum money introduced by Zhandry [55]. Our hybrid payment system employs quantum states as banknotes and a classical blockchain to settle disputes and to keep track of the valid serial numbers. It has several desirable properties: it is decentralized, requiring no trust in any single entity; payments are as quick as quantum communication, regardless of the total number of users; when a quantum banknote is damaged or lost, the rightful owner can recover the lost value.

arXiv:2002.11998•Quantum•Jul 16, 2020•42 citations

Quantum Prudent Contracts with Applications to Bitcoin

Or Sattath

Smart contracts are cryptographic protocols that are enforced without a judiciary. Smart contracts are used occasionally in Bitcoin and are prevalent in Ethereum. Public quantum money improves upon cash we use today, yet the current constructions do not enable smart contracts. In this work, we define and introduce quantum payment schemes, and show how to implement prudent contracts -- a non-trivial subset of the functionality that a network such as Ethereum provides. Examples discussed include: multi-signature wallets in which funds can be spent by any 2-out-of-3 owners; restricted accounts that can send funds only to designated destinations; and "colored coins" that can represent stocks that can be freely traded, and their owner would receive dividends. Our approach is not as universal as the one used in Ethereum since we do not reach a consensus regarding the state of a ledger. We call our proposal prudent contracts to reflect this. The main building block is either quantum tokens for digital signatures (Ben-David and Sattath QCrypt'17, Coladangelo et al. Crypto'21), semi-quantum tokens for digital signatures (Shmueli'22) or one-shot signatures (Amos et al. STOC'20). The solution has all the benefits of public quantum money: no mining is necessary, and the security model is standard (e.g., it is not susceptible to 51\% attacks, as in Bitcoin). Our one-shot signature construction can be used to upgrade the Bitcoin network to a quantum payment scheme. Notable advantages of this approach are: transactions are locally verifiable and without latency, the throughput is unbounded, and most importantly, it would remove the need for Bitcoin mining. Our approach requires a universal large-scale quantum computer and long-term quantum memory; hence we do not expect it to be implementable in the next few years.

arXiv:2204.12806•Apr 27, 2022•5 citations

Public-key Quantum money with a classical bank

Omri Shmueli

Quantum money is a main primitive in quantum cryptography, that enables a bank to distribute to parties in the network, called wallets, unclonable quantum banknotes that serve as a medium of exchange between wallets. While quantum money suggests a theoretical solution to some of the fundamental problems in currency systems, it still requires a strong model to be implemented; quantum computation and a quantum communication infrastructure. A central open question in this context is whether we can have a quantum money scheme that uses "minimal quantumness", namely, local quantum computation and only classical communication.

ACM Symposium on Theory of Computing (STOC)•Jun 9, 2022•21 citations

Quantum-Enhanced Distributed Smart Contracts

Jincheng Zhang

This paper explores the design and implementation of distributed smart contracts leveraging the principles of Quantum Key Distribution (QKD) and Quantum Secure Multi-Party Computation (QSMPC). Traditional smart contracts are vulnerable to various attacks due to the inherent limitations of classical cryptography. This research proposes a novel architecture that integrates QKD for secure key exchange among contract participants and QSMPC for secure execution of contract logic. The core claim is that this combined approach offers a significantly enhanced level of security and reliability compared to existing smart contract systems. The underlying mechanism relies on establishing a quantum-secured channel for key distribution followed by a quantum-resistant multi-party computation protocol. We outline the technical aspects of this system, highlighting the challenges and potential solutions in building a truly quantum-safe distributed smart contract ecosystem. This work addresses a critical need for robust security in decentralized systems and paves the way for applications requiring the highest levels of trust and confidentiality.

•Sep 2, 2026•0 citations

COMPARATIVE STUDY OF BLOCKCHAIN AND QUANTUM CRYPTOGRAPHY FOR SECURE FAIR EXCHANGE

Dr.Sunil Guptha2 Anita Rai1

In decentralized environments where the parties have only partial trust, secure and fair exchange is a must throughout the entire process. Smart contracts, transparency, and unalterable transaction records are the main functionalities that blockchain technology uses to implement fair exchange, while the case of quantum cryptography is different in that it offers robust security through the quantum key distribution method with eavesdropping that is detectable. In this paper, we examine the pros and cons of blockchain-based versus quantum cryptographic models for implementing secure fair exchange. We evaluate the issues that concern security, fairness, efficiency, scalability, and resistance to quantum attacks. The outcome of the analysis reveals that blockchain not only guarantees enforcement and transparency but also that the adoption of quantum cryptography has a tremendous impact on security, thus increasing the robustness and future-readiness of the fair exchange protocols.

International Journal of Engineering Research and Science & Technology•Feb 12, 2024•0 citations

Quantum Computing meets Blockchain: Threats, Opportunities and a Hybrid Secure Architecture

Prof Ashish Bhatnagar, Sanjoli Kaushik, Rohit Gupta

The convergence of Quantum Computing and Blockchain marks a transformative step in secure distributed systems, offering immense potential and serious security challenges. Quantum algorithms like Shor’s and Grover’s threaten classical cryptographic foundations such as ECC and symmetric key systems, making current blockchains vulnerable. This study explores these vulnerabilities and proposes a hybrid quantum-secure blockchain architecture that integrates post-quantum cryptography such as lattice-based and hash-based algorithms with traditional methods for backward compatibility and efficiency. It also highlights how quantum technologies can enhance blockchain performance through faster consensus and smart contract optimization. The paper concludes that adopting hybrid quantum-resistant mechanisms is vital for ensuring blockchain security, scalability, and resilience in the post-quantum era.

Pranjana The Journal of Management Awareness•Jan 1, 2025•0 citations
We put forward the idea that classical blockchains and smart contracts are potentially useful primitives not only for classical cryptography, but for quantum cryptography as well. Abstractly, a smart contract is a functionality that allows parties to deposit funds, and release them upon fulfillment of algorithmically checkable conditions, and can thus be employed as a formal tool to enforce monetary incentives. In this work, we give the first example of the use of smart contracts in a quantum setting. We describe a simple hybrid classical-quantum payment system whose main ingredients are a classical blockchain capable of handling stateful smart contracts, and quantum lightning, a strengthening of public-key quantum money introduced by Zhandry [Eurocrypt 2019]. Our hybrid payment system uses quantum states as banknotes and a classical blockchain to settle disputes and to keep track of the valid serial numbers. It has several desirable properties: it is decentralized, requiring no trust in any single entity; payments are as quick as quantum communication, regardless of the total number of users; when a quantum banknote is damaged or lost, the rightful owner can recover the lost value.
We put forward the idea that classical blockchains and smart contracts are potentially useful primitives not only for classical cryptography, but for quantum cryptography as well. Abstractly, a smart contract is a functionality that allows parties to deposit funds, and release them upon fulfillment of algorithmically checkable conditions, and can thus be employed as a formal tool to enforce monetary incentives. In this work, we give the first example of the use of smart contracts in a quantum setting. We describe a simple hybrid classical-quantum payment system whose main ingredients are a classical blockchain capable of handling stateful smart contracts, and quantum lightning, a strengthening of public-key quantum money introduced by Zhandry [55]. Our hybrid payment system employs quantum states as banknotes and a classical blockchain to settle disputes and to keep track of the valid serial numbers. It has several desirable properties: it is decentralized, requiring no trust in any single entity; payments are as quick as quantum communication, regardless of the total number of users; when a quantum banknote is damaged or lost, the rightful owner can recover the lost value.
Smart contracts are cryptographic protocols that are enforced without a judiciary. Smart contracts are used occasionally in Bitcoin and are prevalent in Ethereum. Public quantum money improves upon cash we use today, yet the current constructions do not enable smart contracts. In this work, we define and introduce quantum payment schemes, and show how to implement prudent contracts -- a non-trivial subset of the functionality that a network such as Ethereum provides. Examples discussed include: multi-signature wallets in which funds can be spent by any 2-out-of-3 owners; restricted accounts that can send funds only to designated destinations; and "colored coins" that can represent stocks that can be freely traded, and their owner would receive dividends. Our approach is not as universal as the one used in Ethereum since we do not reach a consensus regarding the state of a ledger. We call our proposal prudent contracts to reflect this. The main building block is either quantum tokens for digital signatures (Ben-David and Sattath QCrypt'17, Coladangelo et al. Crypto'21), semi-quantum tokens for digital signatures (Shmueli'22) or one-shot signatures (Amos et al. STOC'20). The solution has all the benefits of public quantum money: no mining is necessary, and the security model is standard (e.g., it is not susceptible to 51\% attacks, as in Bitcoin). Our one-shot signature construction can be used to upgrade the Bitcoin network to a quantum payment scheme. Notable advantages of this approach are: transactions are locally verifiable and without latency, the throughput is unbounded, and most importantly, it would remove the need for Bitcoin mining. Our approach requires a universal large-scale quantum computer and long-term quantum memory; hence we do not expect it to be implementable in the next few years.
Quantum money is a main primitive in quantum cryptography, that enables a bank to distribute to parties in the network, called wallets, unclonable quantum banknotes that serve as a medium of exchange between wallets. While quantum money suggests a theoretical solution to some of the fundamental problems in currency systems, it still requires a strong model to be implemented; quantum computation and a quantum communication infrastructure. A central open question in this context is whether we can have a quantum money scheme that uses "minimal quantumness", namely, local quantum computation and only classical communication.
This paper explores the design and implementation of distributed smart contracts leveraging the principles of Quantum Key Distribution (QKD) and Quantum Secure Multi-Party Computation (QSMPC). Traditional smart contracts are vulnerable to various attacks due to the inherent limitations of classical cryptography. This research proposes a novel architecture that integrates QKD for secure key exchange among contract participants and QSMPC for secure execution of contract logic. The core claim is that this combined approach offers a significantly enhanced level of security and reliability compared to existing smart contract systems. The underlying mechanism relies on establishing a quantum-secured channel for key distribution followed by a quantum-resistant multi-party computation protocol. We outline the technical aspects of this system, highlighting the challenges and potential solutions in building a truly quantum-safe distributed smart contract ecosystem. This work addresses a critical need for robust security in decentralized systems and paves the way for applications requiring the highest levels of trust and confidentiality.
In decentralized environments where the parties have only partial trust, secure and fair exchange is a must throughout the entire process. Smart contracts, transparency, and unalterable transaction records are the main functionalities that blockchain technology uses to implement fair exchange, while the case of quantum cryptography is different in that it offers robust security through the quantum key distribution method with eavesdropping that is detectable. In this paper, we examine the pros and cons of blockchain-based versus quantum cryptographic models for implementing secure fair exchange. We evaluate the issues that concern security, fairness, efficiency, scalability, and resistance to quantum attacks. The outcome of the analysis reveals that blockchain not only guarantees enforcement and transparency but also that the adoption of quantum cryptography has a tremendous impact on security, thus increasing the robustness and future-readiness of the fair exchange protocols.
The convergence of Quantum Computing and Blockchain marks a transformative step in secure distributed systems, offering immense potential and serious security challenges. Quantum algorithms like Shor’s and Grover’s threaten classical cryptographic foundations such as ECC and symmetric key systems, making current blockchains vulnerable. This study explores these vulnerabilities and proposes a hybrid quantum-secure blockchain architecture that integrates post-quantum cryptography such as lattice-based and hash-based algorithms with traditional methods for backward compatibility and efficiency. It also highlights how quantum technologies can enhance blockchain performance through faster consensus and smart contract optimization. The paper concludes that adopting hybrid quantum-resistant mechanisms is vital for ensuring blockchain security, scalability, and resilience in the post-quantum era.