Abstract In the 1970s, Wiesner introduced the concept of quantum money, where quantum states serve as currency, offering physical-level unforgeability through quantum mechanics. Yet, traditional proposals often unrealistically assume personal quantum computing access for each user. To address these issues, we propose a cloud-based semi-quantum money (CSQM) scheme. This approach only requires semi-honest third-party quantum clouds, while the rest of the system, including transactions and banks, remains fully classical. We also estimate the computational power required by the quantum cloud and provide a thorough security analysis. Our approach significantly reduces the quantum resource demands on local users and facilitates seamless integration with current classical systems.
Abstract In the 1970s, Wiesner introduced the concept of quantum money, where quantum states serve as currency, offering physical-level unforgeability through quantum mechanics. Yet, traditional proposals often unrealistically assume personal quantum computing access for each user. To address these issues, we propose a cloud-based semi-quantum money (CSQM) scheme. This approach only requires semi-honest third-party quantum clouds, while the rest of the system, including transactions and banks, remains fully classical. We also estimate the computational power required by the quantum cloud and provide a thorough security analysis. Our approach significantly reduces the quantum resource demands on local users and facilitates seamless integration with current classical systems.
Abstract The seminal idea of quantum money, not forgeable due to laws of Quantum Mechanics, proposed by Stephen Wiesner, has laid the foundations for the Quantum Information Theory in the early ’70s. Recently, several other schemes for quantum currencies have been proposed, all, however, relying on the assumption that the quantum source device, acts according to its specification. This makes several known quantum money protocols vulnerable to the so-called hardware Trojan horse attacks. We, therefore, study the following problem: to what extent quantum money schemes can be made independent from the inner working of source and verification-devices used by the honest parties (bank and mint) in creating and processing the quantum money? Drawing inspirations from the semi-device-independent quantum key distribution protocol, we introduce the first scheme of quantum money with this assumption partially relaxed, along with the proof of its unforgeability. Finally, we formulate and discuss a quantum analog of the Oresme–Copernicus–Gresham’s law of economy, that may hold in the future.
Private quantum money allows a bank to mint quantum money states that it can later verify, but that no one else can forge. In classically verifiable quantum money -- introduced by Gavinsky (CCC 2012) -- the verification is done via an interactive protocol between the bank and the user, where the communication is classical, and the computational resources required of the bank are classical. In this work, we consider memoryless interactive protocols in which the minting is likewise classical, and construct a private money scheme that achieves these two notions simultaneously (i.e., classical verification and classical minting). We call such a construction a private semi-quantum money scheme, since all the requirements from the bank in terms of computation and communication are classical.
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.
Quantum money represents an innovative approach to currency by encoding economic value within the quantum states of physical systems, utilizing the principles of quantum mechanics to enhance security, integrity, and transferability. This perspective article explores the definition and properties of quantum money. We analyze the process of transferring quantum money via quantum teleportation, using terrestrial and satellite-based quantum networks. Furthermore, we consider the impact of quantum money on the modern banking system, particularly in money creation. Finally, we conduct an analysis to assess the strengths and weaknesses of quantum money, as well as opportunities and threats associated with this emerging concept.
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.
In a quantum money scheme, a bank can issue money that users cannot counterfeit. Similar to bills of paper money, most quantum money schemes assign a unique serial number to each money state, thus potentially compromising the privacy of the users of quantum money. However in a quantum coins scheme, just like the traditional currency coin scheme, all the money states are exact copies of each other, providing a better level of privacy for the users. A quantum money scheme can be private, i.e., only the bank can verify the money states, or public, meaning anyone can verify. In this work, we propose a way to lift any private quantum coin scheme -- which is known to exist based on the existence of one-way functions, due to Ji, Liu, and Song (CRYPTO'18) -- to a scheme that closely resembles a public quantum coin scheme. Verification of a new coin is done by comparing it to the coins the user already possesses, by using a projector on to the symmetric subspace. No public coin scheme was known prior to this work. It is also the first construction that is very close to a public quantum money scheme and is provably secure based on standard assumptions. Finally, the lifting technique, when instantiated with the private quantum coins scheme~\cite{MS10}, gives rise to the first construction that is close to an inefficient unconditionally secure public quantum money scheme.