The digital currency Bitcoin has had remarkable growth since it was first proposed in 2008. Its distributed nature allows currency transactions without a central authority by using cryptographic methods and a data structure called the blockchain. Imagine that you could run the Bitcoin protocol on a quantum computer. What advantages can be had over classical Bitcoin? This is the question we answer here by introducing Quantum Bitcoin which, among other features, has immediate local verification of transactions. This is a major improvement over classical Bitcoin since we no longer need the computationally-intensive and time-consuming method of recording all transactions in the blockchain. Quantum Bitcoin is the first distributed quantum currency, and this paper introduces the necessary tools including a novel two-stage quantum mining process. In addition, we have counterfeiting resistance, fully anonymous and free transactions, and a smaller footprint than classical Bitcoin.
The digital currency Bitcoin has had remarkable growth since it was first proposed in 2008. Its distributed nature allows currency transactions without a central authority by using cryptographic methods and a data structure called the blockchain. Imagine that you could run the Bitcoin protocol on a quantum computer. What advantages can be had over classical Bitcoin? This is the question we answer here by introducing Quantum Bitcoin which, among other features, has immediate local verification of transactions. This is a major improvement over classical Bitcoin since we no longer need the computationally-intensive and time-consuming method of recording all transactions in the blockchain. Quantum Bitcoin is the first distributed quantum currency, and this paper introduces the necessary tools including a novel two-stage quantum mining process. In addition, we have counterfeiting resistance, fully anonymous and free transactions, and a smaller footprint than classical Bitcoin.
Bitcoin is a digital currency and payment system based on classical cryptographic technologies which works without a central administrator such as in traditional currencies. It has long been questioned what the impact of quantum computing would be on Bitcoin, and cryptocurrencies in general. Here, we analyse three primary directions that quantum computers might have an impact in: mining, security, and forks. We find that in the near-term the impact of quantum computers appear to be rather small for all three directions. The impact of quantum computers would require considerably larger number of qubits and breakthroughs in quantum algorithms to reverse existing hash functions.
Blockchain technology represented by Bitcoin and Ethereum has been deeply developed and widely used due to its broad application prospects such as digital currency and IoT. However, the security of the existing blockchain technologies built on the classical cryptography depends on the computational complexity problem. With the enhancement of the attackers’ computing power, especially the upcoming quantum computers, this kind of security is seriously threatened. Based on quantum hash, quantum SWAP test and quantum teleportation, a quantum blockchain system is proposed with quantum secure communication. In classical cryptographic theory sense, the security of this system is unconditional since it has nothing to do with the attackers’ computing power and computing resources.
The key cryptographic protocols used to secure the internet and financial transactions of today are all susceptible to attack by the development of a sufficiently large quantum computer. One particular area at risk is cryptocurrencies, a market currently worth over 100 billion USD. We investigate the risk posed to Bitcoin, and other cryptocurrencies, by attacks using quantum computers. We find that the proof-of-work used by Bitcoin is relatively resistant to substantial speedup by quantum computers in the next 10 years, mainly because specialized ASIC miners are extremely fast compared to the estimated clock speed of near-term quantum computers. On the other hand, the elliptic curve signature scheme used by Bitcoin is much more at risk, and could be completely broken by a quantum computer as early as 2027, by the most optimistic estimates. We analyze an alternative proof-of-work called Momentum, based on finding collisions in a hash function, that is even more resistant to speedup by a quantum computer. We also review the available post-quantum signature schemes to see which one would best meet the security and efficiency requirements of blockchain applications.
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 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
Bitcoin has two cryptographic layers. SHA-256 secures mining and the hash chain — it has no periodicity, no rhythm, nothing for the quantum Fourier transform to detect. ECDSA secures signatures — it has rhythm, and Shor's algorithm breaks it. The foundation is quantum resistant. The signatures are not — but signatures are a software upgrade. The hash rate is not. Bitcoin is a shadow-mirror coupling: single hash (shadow, local, independent) coupled to blockchain (mirror, global, irreducible) through proof of work, with a self-regulating coupling constant κ ≈ 128,748 measured across 2,906 days and 12 orders of magnitude. Extended construction from Shadow & Mirror: Complementarity of Computation and Consciousness (Ross, 2026).