Universally composable privacy amplification against quantum adversaries

Randomness amplification against no-signaling adversaries using two devices

Recently, a physically realistic protocol amplifying the randomness of Santha-Vazirani sources producing cryptographically secure random bits was proposed; however for reasons of practical relevance, the crucial question remained open whether this can be accomplished under the minimal conditions necessary for the task. Namely, is it possible to achieve randomness amplification using only two no-signaling components and in a situation where the violation of a Bell inequality only guarantees that some outcomes of the device for specific inputs exhibit randomness? Here, we solve this question and…

General Security Definition and Composability for Quantum & Classical Protocols

We generalize the universally composable definition of Canetti to the Quantum World. The basic idea is the same as in the classical world. The main contribution is that we unfold the result in a new model which is well adapted to quantum protocols. We also simplify some aspects of the classical case. In particular, the case of protocols with an arbitrary number of layers of sub-protocols is naturally covered in the proposed model.

Using Hash-Based Signatures to Bootstrap Quantum Key Distribution

Quantum Key Distribution is a secret distribution technique that requires an authenticated channel. This channel is usually created on top of an un-authenticated communication medium using unconditionally secure Message Authentication Codes (MAC) and an initial common secret. We examine the consequences of replacing this MAC algorithm by a cryptographic hash-based signature algorithm, like the Lamport algorithm. We show that provided one-way functions exist, the Lamport algorithm or its variants can be instantiated in a secure way in the Universally Composable sense, and can therefore be plugg…

Simplified BB84 quantum key distribution secure against coherent attacks

Decoy-state quantum key distribution (QKD) has convincingly been shown the core solution to secure key exchange. While standard BB84 protocol needs to prepare and measure all states of two complementary bases, which seriously restricts its real life applications in photonic integration and high speed system. Fortunately, a simplified BB84, only sending and receiving three states, achieves the same asymptotic secret key rate compared with standard BB84 under coherent attacks. In this work, by skillfully exploiting uncertainty relation for smooth entropies, we provide the finite-key security bou…

Experimental quantum key distribution with source flaws

Decoy-state quantum key distribution (QKD) is a standard technique in current quantum cryptographic implementations. Unfortunately, existing experiments have two important drawbacks: the state preparation is assumed to be perfect without errors and the employed security proofs do not fully consider the finite-key effects for general attacks. These two drawbacks mean that existing experiments are not guaranteed to be secure in practice. Here, we perform an experiment that for the first time shows secure QKD with imperfect state preparations over long distances and achieves rigorous finite-key s…

相干单向量子密钥分发的有限密钥分析

Finite-Key Analysis for Coherent One-Way Quantum Key Distribution

本文在通用可组合框架内对COW-QKD变体进行严格的有限密钥安全分析，结合量子剩余哈希引理与Kato不等式推导密钥率公式，确保了对相干攻击的安全性并提升了密钥率，证实了其实际应用的可行性。

Practical post-processing for quantum-key-distribution experiments

Quantum key distribution (QKD) promises unconditionally secure key generation between two distant parties by wisely exploiting properties of quantum mechanics. In QKD, experimental measurements on quantum states are transformed to a secret key and this has to be done in accordance with a security proof. Unfortunately, many theoretical proofs are not readily implementable in experiments and do not consider all practical issues. Therefore, in order to bridge this "practical gap", we integrate a few existing theoretical results together with new developments, in effect producing a simple and comp…

Full security of quantum key distribution from no-signaling constraints

We analyze a cryptographic protocol for generating a distributed secret key from correlations that violate a Bell inequality by a sufficient amount, and prove its security against eavesdroppers, constrained only by the assumption that any information accessible to them must be compatible with the non-signaling principle. The claim holds with respect to the state-of-the-art security definition used in cryptography, known as universally-composable security. The non-signaling assumption only refers to the statistics of measurement outcomes depending on the choices of measurements; hence security …

Amplifying the randomness of weak sources correlated with devices

The problem of device-independent randomness amplification against no-signaling adversaries has so far been studied under the assumption that the weak source of randomness is uncorrelated with the (quantum) devices used in the amplification procedure. In this work, we relax this assumption, and reconsider the original protocol of Colbeck and Renner using a Santha-Vazirani (SV) source. To do so, we introduce an SV-like condition for devices, namely that any string of SV source bits remains weakly random conditioned upon any other bit string from the same SV source and the outputs obtained when …

增强的基于瑞尼熵的后量子密钥协议及其可证明安全性和信息论保证

Enhanced Rényi Entropy-Based Post-Quantum Key Agreement with Provable Security and Information-Theoretic Guarantees

本文提出了一种基于瑞尼熵的后量子密钥协议，通过熵保持操作和秘密共享验证实现可证明安全性和信息论保证，提供 $2^{128}$ 的量子安全保证。

Lightweight authentication for quantum key distribution

Quantum key distribution (QKD) enables unconditionally secure communication between distinct parties using a quantum channel and an authentic public channel. Reducing the portion of quantum-generated secret keys, that is consumed during the authentication procedure, is of significant importance for improving the performance of QKD systems. In the present work, we develop a lightweight authentication protocol for QKD based on a `ping-pong' scheme of authenticity check for QKD. An important feature of this scheme is that the only one authentication tag is generated and transmitted during each of…

QMA完全的量子增强Kyber：基于CHSH非定域性的可证明安全性

QMA Complete Quantum-Enhanced Kyber: Provable Security Through CHSH Nonlocality

针对现有基于格的Kyber后量子密钥封装机制易受混合攻击的问题，提出嵌入CHSH非定域性验证的量子增强Kyber协议，结合格计算安全与量子信息论安全，实现可证明安全的高效密钥协商。

分布式对称密钥建立：一种可扩展的量子安全密钥分发协议

Distributed Symmetric Key Establishment: a Scalable Quantum-Safe Key Distribution Protocol

本文提出分布式对称密钥建立协议DSKE，通过秘密共享实现可扩展的量子安全密钥分发，在通用可组合安全框架下证明其信息论安全性与鲁棒性，并展示了在多种真实环境中的实现，为应对量子计算威胁提供了一种经济高效的解决方案。