Temporal-Angular Quantum Addressing (TAQA) specifies a practical coordination layer for distributed quantum systems that operationalizes cycle-anchored phase-window execution. TAQA is designed for architectures where long-horizon absolute timestamp synchronization cannot be guaranteed and where continuous external timing infrastructure (GNSS, dedicated timing links, etc.) is undesirable, unavailable, or untrusted. Core idea Instead of scheduling actions at an absolute time, TAQA schedules actions by phase conditions on a shared cyclic phase convention \( \phi(t)\in[0,1)\cong \mathbb{S}^1 \) together with an explicit cycle index. Nodes execute when their locally estimated phase enters an agreed wrap-around-safe acceptance window within the intended cycle. This avoids âsame phase / wrong cycleâ ambiguity and supports deterministic coordination under explicit short-horizon error assumptions. What TAQA defines TAQA defines how to express and execute distributed quantum-network actions using classical metadata: Execution primitive (Q-Address style): TAQA expresses each executable action as a macro window + micro slot instruction. The macro window encodes the intended cycle and phase acceptance window; the micro slot provides local sequencing/offset ordering within that window using local hardware timing. Tick-canonical semantics: For interoperability and verification, TAQA adopts fixed-point ticks (integers) as canonical semantics (no floating-point boundary checks). Human-facing displays (HS degrees, HS index, SWT labels, etc.) are derived-only and must not be used for verification or boundary gating. Cycle anchoring: Every executable instruction is explicitly anchored to an intended cycle index to prevent ambiguous interpretation across repeated cycles. Optional audit hook: TAQA supports an optional post-execution signed audit receipt (TSAE-style) using the same tick-canonical context fields, suitable for optional anchoring (e.g., a ledger/Clockchain pattern). What TAQA does NOT define TAQA is a control-plane / metadata layer and does not modify quantum mechanics: It does not introduce a quantum time operator and does not change the Hilbert space. It does not define bootstrapping or clock-parameter estimation algorithms (offset/drift). These are handled by external initialization/tracking layers (e.g., bootstrapping protocols). It does not define cryptographic primitives or threat models. Security is defined by external, versioned security profiles. Applications enabled by TAQA TAQA provides a deterministic coordination layer for common distributed-quantum workflows, including: Phase-aligned distributed gate execution: remote node actions are triggered in the same cycle-anchored window; micro timing is local. Entanglement distribution scheduling: photon emission windows and BSM windows can be scheduled to coincide without continuous absolute-time synchronization. Temporal routing labels: cycle-anchored contexts can be used as temporal labels for routing, prioritization, and scheduling in repeater networks and distributed workflows. Security model (plug-in interface) TAQA treats Timeverse/Q-Address/TSAE fields as public context (not secrets). Security (signatures, nonce policy, anti-replay rules, canonical encoding, algorithm suites) is provided by an external Security Profile selected via a suite identifier (e.g., security_profile_id). TAQA fields may be bound as associated data (domain separation), but confidentiality and integrity are provided by the security layer. Normative dependencies (DOIs) TAQA is interoperable by construction and relies on the following published normative specifications: Phase-Coordination Series Conventions:https://doi.org/10.5281/zenodo.18068999 Q-Address: Macro Phase + Micro Slot:https://doi.org/10.5281/zenodo.18068997 Timeverse Security Profile:https://doi.org/10.5281/zenodo.18069423 Related context Theorem of Temporal Resolution Limitation and the Phase-Coordination Principle (v1.1):https://doi.org/10.5281/zenodo.17955430 Quantum Bootstrapping Protocol (QBP) v1.2:https://doi.org/10.5281/zenodo.18064435 Keywords: TAQA, distributed quantum computing, quantum networks, phase coordination, phase windows, cycle anchoring, Q-Address, ticks, interoperability, control plane, audit receipts, security profiles.
Khang Wen Goh, Burhan Ul Islam Khan, Abdul Raouf Khan, Dwi Sudarno Putra · 6 authors
Blockchain systems built on classical cryptography face immediate risks from large-scale quantum computers, while purely quantum-based blockchains often rely on a single Private Key Generator (PKG) and incur heavy resource overheads. To overcome these issues, this paper proposes a hybrid quantum and post-quantum blockchain approach that removes single points of trust by using Distributed Key Generation and a dual-layer signature mechanism. This method integrates quantum digital signatures, rooted in the Fully Flipped Permutation problem, with classical post-quantum (lattice-based) cryptography, enabling users to switch between quantum and classical signatures according to security requirements and channel conditions. Delegated Proof-of-Stake with node behavior and Borda count has been incorporated to manage consensus, ensuring that witness nodes are regularly re-elected and malicious actors are penalized by distributing secret shares among multiple rotating witnesses. We eliminate the central vulnerability of a sole PKG while maintaining rigorous resistance to collusions. Our analytical model indicates that a fraction of transactions can use quantum signatures without system-wide bottlenecks, while the remaining transactions follow classical PQC paths with throughput approaching classical baselines under our modeling assumptions. Consequently, this hybrid method offers higher scalability, robust collusion resistance, and long-term security even under quantum-capable adversaries. This paper presents extensive theoretical analyses, probability models, and algorithmic complexities, demonstrating that our design provides resilient infrastructure that meets the key performance and security requirements of next-generation blockchain systems.
Secure interoperability across heterogeneous blockchains remains one of the most pressing challenges in Web3 with existing bridge protocols vulnerable to both classical exploits and emerging quantum threats. This paper introduces QLink a quantum-safe Layer 3 interoperability protocol that integrates postquantum cryptography (PQC) quantum key distribution (QKD) and hardware security modules (HSMs) into a unified validator architecture. To our knowledge, QLink is the first interoperability framework to combine these mechanisms to secure validator communication proof aggregation and key management. Validators exchange encryption keys through QKD channels, achieving information-theoretic security against interception, while cross-chain proofs are generated and aggregated with NIST-standardized PQC algorithms. Private keys remain sealed inside HSM enclaves mitigating the risk of theft or leakage. Deployed as a dedicated Layer 3 protocol QLink operates independently of Layer 1 and Layer 2 chains providing a scalable decentralized foundation for secure cross-chain messaging and asset transfer. Experimental evaluation using network simulations demonstrates that validator communication overhead remains sub-second while security guarantees extend beyond current bridge architectures to resist both classical and quantum adversaries. By addressing today vulnerabilities and anticipating future quantum threats QLink establishes a practical and future-proof pathway for blockchain interoperability.
We study non-interactive zero-knowledge proofs (NIZKs) for NP satisfying: 1) statistical soundness, 2) computational zero-knowledge and 3) certified-everlasting zero-knowledge (CE-ZK). The CE-ZK property allows a verifier of a quantum proof to revoke the proof in a way that can be checked (certified) by the prover. Conditioned on successful certification, the verifier's state can be efficiently simulated with only the statement, in a statistically indistinguishable way. Our contributions regarding these certified-everlasting NIZKs (CE-NIZKs) are as follows: - We identify a barrier to obtaining CE-NIZKs in the CRS model via generalizations of known interactive zero-knowledge proofs that satisfy CE-ZK. - We circumvent this by constructing CE-NIZK from black-box use of NIZK for NP satisfying certain properties, along with OWFs. As a result, we obtain CE-NIZKs for NP in the CRS model, based on polynomial hardness of the learning with errors (LWE) assumption. - In addition, we observe that the aforementioned barrier does not apply to the shared EPR model. We leverage this fact to construct a CE-NIZK for NP in this model based on any statistical binding hidden-bits generator, which can be based on LWE. The only quantum computation in this protocol involves single-qubit measurements of the shared EPR pairs.
This is the fourth and most comprehensive edition of the theoretical framework introduced in the original preprint (DOI: 10.5281/zenodo.17834958). The Universal Distributed Architecture (UDA) proposes a three-dimensional quantum blockchain of Planck-scale quantum cubes governed by a novel Proof-of-Consciousness (PoC) consensus protocol. Five core equations are rigorously derived and proven: the PoC consensus operator (Kraus representation), the Absolute validator state, ledger entropy growth rate (Lindblad form), OAM entanglement threshold, and quantum-resistant hash function. The work integrates loop quantum gravity, AdS/CFT correspondence, the Sachdev-Ye-Kitaev (SYK) model, JT gravity, and holographic tensor networks (MERA, PEPS, and 5D extensions), together with five-dimensional optical memory crystals (University of Southampton) as an experimental substrate, with equations 27â34 establishing Rayleigh scattering as a physical implementation of holographic hash verification and a room-temperature experimental protocol. Version 4 introduces three structural advances. (1) A ledger isomorphism (Proposition 0): every axiom of a distributed append-only ledger â immutability, decentralized consensus, append-only ordering, bounded block capacity, and double-spend prohibition â is shown to be independently realized by an established physical principle (no-cloning/no-deleting theorems, quantum Darwinism, the second law, the BekensteinâBousso bound, and monogamy of entanglement), localizing UDA's novel content entirely in the validation rule. (2) An operational, laboratory-reproducible definition of the consciousness quantity, |Q| = m/m_P = Ï_C·t_P, integrating Inomata's pan-psychist quantity Q = iâG·M and measurable through three independent channels: Compton-clock interferometry and gravitationally induced entanglement (BMV), a standardized measurement-induced-phase-transition (Q-MIPT) meter on quantum processors with explicit calibration and uncertainty budget, and collider bounds on event-driven non-unitarity anchored by ATLAS/CMS top-quark entanglement and neutral-kaon CPT interferometry. The channel-universality law Q_G = Q_I = Q_C is the flagship prediction exclusive to UDA. (3) A sharp mathematical distinction between the anti-Hermitian consciousness operator (magnitude of agency: write capacity per Planck tick) and the Hermitian moral operator (valence of agency: mutual-information gain per unit entropy budget), with an explicit laboratory protocol distinguishing them. The framework further develops a SYKâConsciousness correspondence with non-Hermitian topological phases, MIPT modulated by consciousness density, and non-Hermitian MERA networks exhibiting a Holographic Skin Effect that topologically protects conscious information at the holographic boundary. UDA's non-unitarity is event-driven rather than continuous, making it consistent by construction with DiĂłsiâPenrose bounds and separable from collapse models in a single two-parameter experiment (Discriminator D1). Falsifiable predictions are organized in two tiers â five UDA-exclusive predictions (2026â2030), each with its own falsification clause, and inherited consistency tests â alongside detailed QuTiP simulations, NV-center and 5D crystal protocols, and applications in quantum computing, quantum AI, and high-energy tests at the LHC and FCC. The framework resolves the von Neumann measurement chain via dual observation and portrays the universe as a growing, error-corrected quantum ledger.
I formalize the Arquitectura Universal Distribuida (AUD) as a three-dimensional quantum blockchain of Planck-scale âquantum cubesâ governed by the novel Proof-of-Consciousness (PoC) consensus protocol. Each cube acts as a Loop Quantum Gravity spin-network node and full validator. Information is stored holographically via universal entanglement, providing a provably unclonable hash function. The global validator â the Absolute â enforces non-local consensus through Bell-inequality violations and high-energy entanglement observed at the LHC. The model resolves the von Neumann measurement chain and predicts observable deviations in entanglement entropy growth.
On-demand authentication is critical for scalable quantum systems, yet many existing quantum signature and message-authentication schemes are signer-initiated, requiring advance distribution of authentication material even when no verification occurs. We introduce verifier-initiated quantum digital signatures (VIQDS), in which the verifier requests authentication only when needed and the signer responds once; after issuance, verification proceeds without further interaction. Practically, shifting authentication to a verifier-driven, on-demand workflow reduces avoidable communication and storage overhead and aligns with deployments where verification is sporadic, such as distributed services and audit-oriented infrastructures. Our approach leverages quantum zero-knowledge techniques so that verification reveals nothing about the signerâs secret key beyond the fact that the signature is valid. We present a general conversion principle from suitable quantum proof protocols to VIQDS, together with a concrete realization based on elementary qubit platforms. Here, we show information-theoretic security against forgery and privacy against curious verifiers without computational hardness assumptions. The authors introduce a verifier-initiated quantum message-authentication method, in which authentication is requested only when needed. Their approach uses quantum zero knowledge techniques to protect information about the signerâs secret key while providing information-theoretic security against forgery
Blockchain technology has emerged as the backbone of cryptocurrencies and decentralized finance, yet its long-term resilience is increasingly threatened by advances in quantum computing. Quantum algorithms, such as Shorâs algorithm, can undermine public-key cryptography, while Groverâs algorithm accelerates brute-force search, weakening proof-of-work schemes. In this paper, we propose a Quantum Blockchain Framework that integrates quantum communication protocols, quantum consensus mechanisms, and quantum-resistant cryptography. We construct a theoretical model of quantum-secured distributed ledgers, where qubits, entanglement, and quantum key distribution (QKD) enhance security and efficiency. Applications to cryptocurrency are explored, highlighting how quantum blockchain can mitigate security risks, improve consensus speed, and enable quantum-native digital assets.
The transition to post-quantum cryptography poses an unprecedented challenge for Bitcoin and Ethereum, as it involves implementing a defensive downgrade that imposes immediate, severe costs with no tangible benefits. While quantum computers capable of breaking secp256k1 require between 523â2,500 logical qubits, with the author deriving 523 logical qubits as an algorithmic lower bound (not inclusive of arithmetic and ancilla qubits) for a canonical Shor/phase-estimation circuit using the formula QL = 2âlog2(n)â + 2 + âlog2(2 + 1/(2Δ))â for Δ = 0.001, and conservative estimates ranging up to 2,500 logical qubits based on comprehensive resource modelsâsignificantly less than the 2,100â2,400 logical qubits es- timated for general elliptic curvesâcurrent systems achieve only âŒ100 logical qubits. IBMâs quantum roadmap projects 500â1,000 logical qubits by 2029, placing the critical threshold within 4â10 years depending on which estimate proves accurate. This timeline collides with the reality that convincing decentralized communities to accept 50% capacity loss and 2â 3Ă fee increases may take 10â15 years in themselves, based on historical governance patterns where even beneficial upgrades required 2â5+ years. Current testnet implementations on per- missioned systems show measurable performance degradation. Critically, this data comes from fundamentally different architectures than permissionless networks, which will likely experience 30â50% additional performance degradation due to global verification requirements, heterogeneous hardware, and compounding propagation delays. This methodological limitationâextrapolating from permissioned to permissionless systemsârepresents a critical infrastructure failure that introduces massive uncertainty into migration planning. Com- pounding this challenge, secp256k1 is not officially approved by NIST under FIPS 186-5 or SP 800-186, creating additional regulatory vulnerabilities. Beyond transient impacts, PQC creates permanent state bloat, with quantum-resistant accounts requiring 59 times more storage (1,952 bytes / 33 bytes = 59.2Ă for ML-DSA-65), thereby accelerating centralization- tion. This paper presents a comprehensive framework acknowledging these harsh realities. While we propose specific BIP/EIP implementations and optimization strategies that might achieve 50â60% capacity retention, we recognize that the quantum threat timeline may now be shorter than even the minimum viable migration period. Unlike beneficial upgrades like SegWit (which took 20 months for activation and 5+ years for 50% adoption despite offering improvements), PQC migration is a purely defensive measure imposing only costs. The stark reality: blockchain communities must choose between accepting immediate emergency action or facing quantum vulnerability by 2029.
Jamil Abedalrahim Jamil Alsayaydeh, Mohd Faizal Yusof, Nor Adnan Yahaya, Viacheslav Kovtun · 5 authors
In today's digital world, cryptocurrencies like Bitcoin can secure transactions without banks. However, the rise of quantum computing poses significant threats to their security, as traditional cryptographic methods may be easily compromised. In addition, the existing algorithms face difficulties like slow transaction speeds, interoperability issues between different cryptocurrencies, and privacy concerns. Hence, Quantum Crypto Guard for Secure Transactions (QCG-ST), a novel blockchain framework, is introduced, offering enhanced security and efficiency for cryptocurrency transactions. The QCG-ST employs lattice-based cryptography to provide robust protection against quantum threats and incorporates a new consensus mechanism to increase the transaction speed and reduce energy consumption. The QCG-ST system uses lattice-based encryption that is based on the Ring Learning With Errors (Ring-LWE) issue to protect itself from quantum assaults. It uses sharding, a Proof-of-Stake (PoS) consensus method, and a threshold signature scheme (TSS) to make the system more scalable and use less energy. Zero-knowledge proofs (ZKPs) are used to check transactions without giving out private information. We offer a cross-chain atomic swap protocol that uses hashed time-lock contracts to make sure that it works on all platforms. Blockchain transaction data utilized in testing originated from the Bitcoin Historical Dataset available on Kaggle, and quantum resistance has been assessed using the Qiskit Aer simulator. It evaluated the framework's performance to that of traditional methods like Payment Channel-Lightning Network (PC-LN), Variational Quantum Eigensolver (VQE), and Cross-Chain Transaction with Hyperledger (CCT-H). Results show that QCG-ST does far better than traditional systems in terms of transaction success rate (up to 98.5%), speed, energy efficiency, latency, and throughput, especially when tested in a quantum-simulated environment. This study completes in an essential vacuum in blockchain technology by suggesting a strong, quantum-resistant, privacy-protecting architecture that can handle the problems that could arise up in decentralized digital banking in the future.
Quantum computing stands poised to transform numerous fields of modern technology by offering computational capabilities beyond those of classical systems. This survey offers a detailed analysis of major fields, such as artificial intelligence and machine learning (AI/ML), blockchain, cybersecurity, and digital communication, highlighting how they are significantly transformed through advancements in quantum computing. It presents a comparative analysis of current quantum computing paradigms and architectures, and examines major quantum algorithms such as Shorâs integer factorization algorithm, Groverâs search algorithm, and hybrid quantumâclassical approaches like QAOA and VQE, highlighting their implications for real-world problem solving. Significant advancements in quantum hardware are surveyed, from increasing qubit counts and improved coherence to progress in error mitigation and emerging quantum processor technologies, and their impact on near-term and long-term computing capabilities is evaluated. Finally, the current limitations of quantum computing are discussed, and forward-looking insights into future research directions are provided, outlining the path toward fully harnessing quantum power across industries.
Collins Izuchukwu Okafor, Love Allen Chijioke Ahakonye, Jae Min Lee, DongâSeong Kim
Integrating Internet of Things (IoT) networks with blockchain technology has introduced transformative potential for secure, decentralized applications. However, with expanding IoT networks and the rapid advancements in quantum computing, which can break the classical encryption mechanism employed in these networks, securing validator communications in blockchain consensus mechanisms becomes increasingly challenging. This study presents PureQuantum, a novel quantum-enhanced framework that integrates quantum key distribution (QKD) into a proof-of-authority and association (PoA 2 ) consensus mechanism. Our experimental evaluation demonstrates that PureQuantum achieves a key generation time of approximately 2.315 s (BB84) and an average error rate of 0.2493, thereby ensuring robust resistance to classical and quantum computational threats. Exploring the architecture, design, and performance of PureQuantum, this concept highlights its ability to balance scalability, energy efficiency, and quantum-resilient security. By integrating QKD into validator communication protocols, PureQuantum provides a future-proof framework capable of supporting the demands of IoT-enabled decentralized systems.
Quantum pseudorandomness is an emerging research area. Ji, Liu, and Song defined pseudorandom states (PRSs) and pseudorandom unitaries (PRUs) as quantum analogs of pseudorandom generators and pseudorandom functions. A unitary oracle separation result between one-way functions and PRSs/PRUs, established by Kretschmer, suggests that certain quantum primitives may remain secure even if classical cryptography is compromised. This insight has spurred extensive work on quantum pseudorandomness and its applications in quantum cryptography. Many constructions of PRSs have been established under standard assumptions, yet building a secure PRU was a long-standing open problem. This dissertation aims to narrow the gap between PRSs and PRUs and presents results that go beyond PRSs. We introduce Pseudorandom State Scramblers (PRSSs), a new primitive that lies between PRSs and PRUs. A PRSS maps any pure state to a pseudorandom state, a property shared with PRUs but not with PRSs. We present a construction of PRSSs inspired by the well-known Kacâs walk, and in particular, we develop a parallel variant that significantly accelerates the mixing time, enabling an efficient construction. PRSSs support cryptographic tasks not known to be achievable from PRSs alone, including a quantum encryption scheme and a succinct quantum state commitment. Additionally, when suitable classical randomness is provided, our construction exhibits a special dispersing property not known to be satisfied by any existing construction of quantum pseudorandom primitives. Our subsequent work shows that, without asymptotically increasing the number of steps, our construction based on the parallel Kacâs walk yields PRUs with standard or even strong security. The proof builds on a recently developed technique for establishing adaptive security, known as the path-recording method. This result provides an alternative construction of PRUs and further showcases the power of this proof technique. In addition, this dissertation includes two side projects. The first revisits the Hidden Subgroup Problem over â€n, providing a simplified analysis of a known quantum algorithm using elementary lattice tools. The second establishes a quantum analogue of a classical impossibility result for statistical non-interactive zero-knowledge arguments, showing limitations of black-box reductions under classical-query quantum adversaries.
N. Ramanjaneya Reddy, Supriya Suryadevara, K. Guru Raghavendra Reddy, R. Umamaheswari · 6 authors
Quantum computing is an evolution of classical computing, capable of solving problems that are competitive enough to break the existing cryptographic primitives upon which current blockchain systems are based. Popular schemes like RSA, ECDSA, and SHA-256 can be compromised by quantum algorithms (Shor's and Grover's), raising questions about the security and trustworthiness of blockchain-based applications in finance, healthcare, and supply chains. Many current approaches focus on isolated aspects of the blockchain, such as cryptographic primitives or key exchange, without a comprehensive strategy that can guarantee end-to-end security in the face of a quantum threat. Finally, traditional consensus mechanisms such as Proof-of-Work and Proof-of-Stake are vulnerable to Sybil attacks, centralization, and leader-selection bias. When the adversary has access to a quantum computer, these issues become significantly worse. In this paper, we present QuantumShield-BC, a modular blockchain framework incorporating post-quantum cryptographic signatures, quantum key distribution (QKD), and a novel Quantum Byzantine Fault Tolerance (Q-BFT) consensus mechanism driven by quantum random number generation (QRNG) to address these challenges. QKD: The system supports tamper-proof key exchange, quantum-resilient consensus among validator nodes, and secure transaction signing. Experimental evaluation demonstrates that QuantumShield-BC achieves low consensus latency and high throughput, while providing perfect security against simulated attacks from Shor's and Grover's algorithms. The proposed framework eradicates the Sybil attack effectiveness up to 0%, eliminates replay and MITM vulnerabilities, and achieves an average throughput of over 7,000 transactions per second with 100 validators, orders of magnitude better than classical blockchain systems. The importance of each quantum part to the system's robustness is also demonstrated using an ablation study. With its unique ability to provide a post-quantum framework for high-assurance, general-purpose, scalable, and interoperable blockchain networks resistant to quantum-inspired attacks or quantum retrieval, QuantumShield-BC is practical for deployment in critical infrastructure and digital trust ecosystems where performance and a future-proof foundation are essential.
S. Jagan, B. Girirajan, Manisha Bhimrao Mane, Hussana Johar R B · 6 authors
The convergence of quantum computing and artificial intelligence (AI) has introduced innovative opportunities to accelerate deep learning, particularly within decentralized cloud architectures. This study develops an adaptive quantum AI model leveraging hybrid quantum-classical algorithms to optimize deep learning processes such as training, inference, and resource allocation. The proposed model integrates Variational Quantum Circuits (VQCs) and Quantum Approximate Optimization Algorithms (QAOAs), which enable efficient handling of high-dimensional data and complex optimization tasks inherent in distributed environments. By addressing challenges like latency, energy efficiency, and computational overhead, the quantum AI model demonstrates significant performance gains in decentralized cloud systems.Experimental evaluations on benchmark datasets reveal a 40% reduction in training time, a 30% improvement in resource efficiency, and a 20% increase in prediction accuracy compared to classical deep learning frameworks. This study highlights the transformative potential of quantum computing in AI-driven decentralized cloud architectures, offering insights into its application for computationally intensive tasks across industries such as healthcare, finance, and logistics. Future work will focus on refining quantum hardware compatibility, developing quantum error correction methods, and exploring federated learning applications to expand the scope of quantum AI in privacy-preserving and distributed systems.
Marija MikiÄ, Mihajlo Srbakoski, Strahinja Praska
The integration of privacy-preserving transactions into public blockchains such as Ethereum remains a major challenge. The Stealth Address Protocol (SAP) provides recipient anonymity by generating unlinkable stealth addresses. Existing SAPs, such as the Dual-Key Stealth Address Protocol and the Curvy Protocol, have shown significant improvements in efficiency, but remain vulnerable to quantum attacks. Post-quantum SAPs based on lattice-based cryptography, such as the Module-LWE SAP, on the other hand, offer quantum resistance while achieving better performance. In this paper, we present a novel hybrid SAP that combines the Curvy protocol with the computational advantages of the Module-LWE technique while remaining Ethereum-friendly. In contrast to full post-quantum solutions, our approach does not provide quantum security, but achieves a significant speedup in scanning the ephemeral public key registry, about three times faster than the Curvy protocol. We present a detailed cryptographic construction of our protocol and compare its performance with existing solutions. Our results prove that this hybrid approach is the most efficient Ethereum-compatible SAP to date.
The emergence of quantum computing has provided new paradigms for cryptography. On the one hand, it poses significant new threats to existing classically cryptographic systems, requiring the community to define new security models that capture what a quantum adversary can do. On the other hand, it gives us new tools to design cryptographic protocols, with weaker assumptions than in the classical world, or even protocols that are impossible classically. In this survey, we first give an overview of new security definitions for classical cryptography, considering quantum adversaries who can either only use local quantum computation (post-quantum security), or even send quantum messages and in particular have access to oracle in superposition (quantum security). We explore these new notions through the examples of commitments, zero-knowledge proofs, encryption, and signatures. Then, we present what is arguably the most famous application of quantum cryptography: quantum key distribution (QKD) protocols that take advantage of unique properties of quantum mechanics to provide secure communication unconditionally. We also explore cryptography beyond QKD, focusing on unclonable cryptography: a family of cryptographic functionalities, built with quantum states, and designed to be resistant to counterfeit by leveraging the âno-cloningâ theorem. We examine in particular quantum money, but also the recent notions of unclonable encryption and copy-protection, including related variants. By presenting a comprehensive survey of these topics, this paper aims to provide a thorough understanding of the current landscape and future potential of quantum cryptography.
Bit commitment is a fundamental cryptographic primitive and a cornerstone for numerous two-party cryptographic protocols, including zero-knowledge proofs. However, it has been proven that unconditionally secure bit commitment, both classical and quantum, is impossible. In this work, we demonstrate that imposing a restriction on the committing party to perform only separable operations enables secure quantum bit commitment schemes. Specifically, we prove that in any perfectly hiding bit commitment protocol, an honestly-committing party limited to separable operations will be detected with high probability if they attempt to alter their commitment. To illustrate our findings, we present an example protocol.
Non-interactive zero-knowledge (NIZK) proof systems are a cornerstone of modern cryptography, but their security has received little attention in the quantum settings. Motivated by improving our understanding of this fundamental primitive against quantum adversaries, we propose a new definition of security against quantum adversary. Specifically, we define the notion of quantum simulation soundness (SS-NIZK), that allows the adversary to access the simulator in superposition. We show a separation between post-quantum and quantum security of SS-NIZK, and prove that Sahaiâs construction for SS-NIZK (in the CRS model) can be made quantumly-simulation-sound. As an immediate application of our new notion, we prove the security of the Naor-Yung paradigm in the quantum settings, with respect to a strong quantum IND-CCA security notion. This provides the quantum analogue of the classical dual key approach to prove the security of encryption schemes. Along the way, we introduce a new notion of quantum-query advantage functions, which may be used as a general framework to show classical/quantum separation for other cryptographic primitives, and it may be of independent interest.
Abstract Blockchain technology ensures accountability, transparency, and redundancy, but its reliance on publicâkey cryptography makes it vulnerable to quantum computing threats. This article addresses the urgent need for quantumâsafe blockchain solutions by integrating postâquantum cryptography (PQC) into blockchain frameworks. Utilizing algorithms from the NIST PQC standardization process, it is aimed to fortify blockchain security and resilience, particularly for IoT and embedded systems. Despite the importance of PQC, its implementation in blockchain systems tailored for embedded environments remains underexplored. A quantumâsecure blockchain architecture is proposed, evaluating various PQC primitives and optimizing transaction sizes through techniques such as publicâkey recovery for Falcon, achieving up to 17% reduction in transaction size. The analysis identifies Falconâ512 as the most suitable algorithm for quantumâsecure blockchains in computerâbased environments and XMSS as a viable but unsatisfactory stateful alternative. However, for embeddedâbased blockchains, Dilithium demonstrates a higher transactionsâperâsecond (TPS) rate compared to Falcon, primarily due to Falcon's slower signing performance on ARM CPUs. This highlights the signing time as a critical limiting factor within embedded blockchains. Additionally, smart contract functionality is integrated, assessing the impact of PQC on smart contract authentication. The findings demonstrate the feasibility and practicality, paving the way for robust and futureâproof IoT applications.
Atoms and photons, two things so different but yet so alike. The former, the building block of matter, something we learn about in school and imagine it as some tiny marbles encircled by other tinier marbles. The latter, an electromagnetic wave, a light particle or an excitation of the electromagnetic field. Quantum mechanics tells us about the properties of these two entities. And even if it sounds, looks and writes counter-intuitive, it has proven right for over a century now. In this work, I elaborate on how we tested the laws of quantum mechanics and how we used them learn more about the tiny building blocks of nature and the fields they use to talk to each other. The atoms we use, are artificial. Superconducting qubits, small electrical circuits with quantized energy levels behave like electrons that transition between different orbitals in an atom. One of the qubits' advantages, is also a big disadvantage. We design the circuits' energy levels and fabricate them in a cleanroom. This allows for arbitrary spaced energy levels but in contrast to real atoms, prevents two superconducting qubits from being alike. Still, this qubit platform is one of the frontrunners for future quantum computing technology and testing fundamental physics due to their scalability. We interface superconducting qubits, which operate in the GHz regime, with microwave photons. We use 3D aluminum cavities as mediators between qubits and photons. The cavities allow for non-destructive readout of the qubit state, they shield the qubits from noise at the qubit frequency and they give us an easy way to frequency-tune these joint systems. We need to operate superconducting qubits and their cavities at millikelvin temperatures in dilution refrigerators. At higher temperatures, superconductivity suffers and even worse, the environment is filled with thermal noise photons. This poses a fundamental limitation on the scalability of superconducting qubit devices. Also connecting multiple devices in different fridges does not work over room temperature links because the microwave photons used for this purpose will be covered in noise and the quantum information they carry, will be unusable. Infrared photons do not suffer from this noise problem since there are close to zero thermal noise photons at their frequencies at room temperature. We cannot simply interface superconducting devices with optical photons due their frequency mismatch and the destructive effect of optical photons on superconductors. Therefore, we use microwave-to-optics transducers that allow to convert microwave photons into optical ones and vice-versa. The transducers that we use are macroscopic electro-optic transducers using the Pockels effect in a disk-shaped Lithium Niobate whispering gallery mode resonator. By using a strong optical pump, photons from the two frequency domains experience a beam-splitter interaction and get converted from one to the other. We measure the generated optical photons using elaborate optical setups, optical heterodyning and single photon detectors to gain knowledge about the qubit state or the converted microwave photons. Bridging the microwave and the optical world allows us to take advantage of both of their strengths but it also requires deep knowledge about both of their working principles. In this work, we describe two experiments that our group conducted to showcase the opportunities that arise from interfacing superconducting qubits with optical photons but also the pitfalls, one may encounter on the way. In the first experiment, we managed to all-optically read out a superconducting qubit. We show that the assignment fidelity, the probability that a measurement of the qubit state matches the prepared state, is close to equal for all-optical, microwave-to-optics and conventional microwave readout. We show T1 and T2 measurements for all three readout types and give an analysis of the noise caused by the optics. Finally, we show that the infrared light does not affect the qubit performance in a negative way but that the heating it causes does. This is an important insight that we used in the next experiment. The second experiment is the upconversion of itinerant single microwave photons to the optical domain. We show that we can generate single microwave photons from a qubit-cavity system. We upconvert these single photons, measure them with a single photon detector and reconstruct their shape. By conducting a single photon Rabi measurement, we show correlations between the microwave and the optical domain. And by thorough signal-to-noise measurements and noise analysis, we find that we can generate single infrared photons with high signal-to-noise ratio 5.1 and low transducer added noise (<0.012 quanta). We show that this measurement creates a path towards entanglement of a superconducting qubit and an optical photon and what parameters need to be improved to achieve it. Additionally, this experiment is a proof of principle for an on-demand infrared single photon source. More generally, it allows to link microwave quantum technology in general to the optical domain.
Blockchain technology has revolutionized secure and decentralized digital transactions. However, the emergence of quantum computing presents a significant threat to traditional cryptographic protocols, particularly public-key encryption mechanisms such as RSA and Elliptic Curve Cryptography (ECC). Quantum computers, leveraging Shorâs and Groverâs algorithms, can efficiently break these encryption schemes, compromising blockchain security. This paper explores quantum-secure blockchain protocols that integrate post-quantum cryptographic (PQC) techniques such as lattice-based, hash-based, and code-based cryptography to resist quantum attacks. Additionally, we evaluate quantum-resistant consensus mechanisms like Quantum-Secure Proof of Stake (QS-PoS) and Quantum-Protected Byzantine Fault Tolerance (Q-BFT). Through simulation-based performance analysis, we demonstrate that quantum-safe blockchain models can achieve robust security while maintaining efficient transaction processing. Our findings suggest that a hybrid approach, combining classical cryptographic elements with post-quantum algorithms, provides the best balance between security, performance, and scalability.