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arXiv:2502.18378

Multi-Channel Currency: A Secure Method Using Semi-Quantum Tokens

Yichi Zhang, Siyuan Jin, Yuhan Huang, Qiming Shao

Published Feb 25, 2025• 0 citations
arXivHTMLPDF

Abstract

Digital currencies primarily operate online, but there is growing interest in enabling offline transactions to improve digital inclusion. Existing offline methods struggle with double-spending risks, often limiting transaction amounts. In this work, we propose a quantum-state-based currency system that uses the non-cloning theorem to enable secure, multi-channel transactions without the risk of double spending. We demonstrate this system's implementation with experimental results, including use cases for currency transfers and swaps. To mitigate credit risks in swaps, we also integrate blockchain to show its wide applicability. Our approach paves the way for quantum-secure digital currencies and opens new possibilities for optimizing multi-channel tokens.

DOI
10.48550/arxiv.2502.18378

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Digital currencies primarily operate online, but there is growing interest in enabling offline transactions to improve digital inclusion. Existing offline methods struggle with double-spending risks, often limiting transaction amounts. In this work, we propose a quantum-state-based currency system that uses the non-cloning theorem to enable secure, multi-channel transactions without the risk of double spending. We demonstrate this system's implementation with experimental results, including use cases for currency transfers and swaps. To mitigate credit risks in swaps, we also integrate blockchain to show its wide applicability. Our approach paves the way for quantum-secure digital currencies and opens new possibilities for optimizing multi-channel tokens.
A digital currency is money in a digital form. In this model, maintaining integrity of the supply is a core concern, therefore protections against double-spending are often at the heart of a secure digital money scheme. Quantum money exploits the quantum mechanical principle of no-cloning to enable a currency that is immune to double spending. One of the challenges of the scheme is that users require technology that is currently out of reach. Here, we propose a model for quantum currency, which alleviates the need for quantum wallets by delegating quantum storage and processing to an intermediary that we call a quantum vault. We develop the basic building blocks of this quantum-enabled digital currency and discuss its benefits and challenges.
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.
Decentralized system allows trustless collaboration among distributed participants directly without a central authority. Naturally, the system highly relies on cryptography to ensure information security and fairness. Classical cryptography is mostly based on the hardness assumption that can be solved by a quantum computer in polynomial time. Therefore, the research on quantum and post-quantum cryptography is becoming more and more important. This thesis explores how quantum information technology enhance the data-security in decentralized system from two different aspects. The first one involves the quantum solution of secure aggregation problem in multi-party secure computation without classical hardness assumptions. The quantum secure aggregation protocol uses decoy states and entangled quantum states to calculate the average of private numbers and detect inside or outside attacks. We analyze the protocol’s security and accuracy, also demonstrate numerical experiments to simulate the effectiveness. In the second one, we analyze the current quantum money protocols and propose the improved protocol which requires less quantum resources and support more functions. The cloud-based quantum money scheme allows the quantum money ecosystem to run on only semi-honest quantum cloud and classical participants and channels. Going a step further, the multi-channel currency scheme provides more kinds of secure transaction channels for choosing. In addition, we issue and transfer quantum currency on a real blockchain for the first time.
Blockchain is a decentralized system that allows transaction transmission and storage according to the roles of the Consensus algorithm and Smart contracts. Non-fungible tokens (NFTs) consolidate the best characteristics of blockchain technology to deliver unique and bona fide tokens, each with distinctive attributes with non-fungible resources. Unfortunately, current classical NFTs are suffering from high costs regarding the consumed power of mining and lack of security. Therefore, this paper presents a new protocol for preparing quantum non-fungible tokens where a quantum state representing NFT is mounted on a blockchain instead of physically giving it to the owner. The proposed scheme is simulated and analyzed against various attacks and proves its ability to secure against them. Furthermore, the presented protocol provides reliable and cheaper NFTs than the classical one.
In this work we present a publicly verifiable quantum money protocol which assumes close to no quantum computational capabilities. We rely on one-time memories which in turn can be built from quantum conjugate coding and hardware-based assumptions. Specifically, our scheme allows for a limited number of verifications and also allows for quantum tokens for digital signatures. Double spending is prevented by the no-cloning principle of conjugate coding states. An implementation of the concepts presented in this work can be found at https://github.com/neverlocal/otm_billz.
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