Blockchain Papers

Benedikt Bünz, Ben Fisch

No abstract is available for this record.

Yu Cao, Xuehui Du, Xiangyu Wu, Qiantao Yang · 6 authors

No abstract is available for this record.

Khalid Mrabet, Faissal El Bouanani, Hussain Ben-Azza

Reputation management systems are essential for establishing trust among network users. They are tools for reinforcing cooperation and sanctioning malicious behavior. This importance becomes a requirement in decentralized environments such as mobile ad-hoc networks (MANETs), peer-to-peer systems (P2P), wireless sensor networks (WSNs), or decentralized social networks (DSNs) where there is no trusted third party to monitor and enforce good behavior among users. In this paper, we propose a dynamic decentralized reputation system that fits such network characteristics, namely decentralization, dynamism, and openness, without conceding on security. The novel system is a general-purpose system that uses blockchain to gather and supply global reputation information while remaining fully decentralized. Unlike previous works on decentralized reputation systems where reputation information is inconsistent and limited to users’ direct experience and recommendations from peers (neighbors), our system gathers feedback from all over the network and stores reputation information on a distributed ledger fully accessible to all users. In terms of security, the proposed method achieves privacy utilizing secure multiparty computation, a cryptographic primitive that preserves feedback privacy even with a dishonest majority reaching$n-2$malicious parties while requiring only$O(n)$messages. The employed techniques enable the system to achieve unique characteristics like consistency, conservation, and verifiability in addition to privacy. The security analysis we provide confirms these properties, and the performed simulation shows the protocol’s effectiveness.

Akash Madhusudan, Mahdi Sedaghat, Samarth Tiwari, Kelong Cong · 5 authors

No abstract is available for this record.

Valerie Fetzer, Michael Klooß, Jörn Müller‐Quade, Markus Raiber · 5 authors

No abstract is available for this record.

Hongqing Liu, Chaoping Xing, Yanjiang Yang, Chen Yuan

No abstract is available for this record.

Gaurav Sarraf

The healthcare industry faces several security, privacy, and data integrity issues; blockchain technology provides a strong foundation to handle these issues. Traditional healthcare systems face issues such as unauthorized data access, breaches, and lack of interoperability across heterogeneous infrastructures. By leveraging decentralization, immutability, and consensus mechanisms, blockchain enables privacy-preserving data sharing and patient-centric identity management through Self-Sovereign Identity (SSI) frameworks. Cryptographic techniques such as Secure Multi-Party Computation (SMPC), Zero-Knowledge Proofs (ZKP), homomorphic encryption, commitment schemes, and many more provide the privacy of computation, the verification of consent, and the security of interactions among healthcare professionals, research institutions, and patients. Smart contracts further streamline automated processes, such as consent management, clinical trials, and electronic health record (EHR) transactions. Despite these advantages, challenges remain in scalability, key management, regulatory compliance, and usability. This review explores blockchain-based architectures, cryptographic methods, and privacy-preserving strategies, emphasizing their potential to strengthen trust, enhance security, and enable interoperable, efficient, and patient-centric healthcare systems while adhering to emerging global data protection standards.

Po-Chu Hsu, Atsuko Miyaji

An auction is commonly used to sell limited resources in modern society.M+ 1st-price auction sellsMidentical goods toBbidders. The topMwinners can buy the goods at theM+1st-price. Each bidder sends their bids secretly as a bit-slice bidding vector to a trusted manager. Bit-slice is commonly used to compare secret values without revealing them. However, the bit-slice bidding vector also limits the upper bound of a bid as the length of the bidding vector. A binary format bidding vector was proposed to increase the bid upper bound to an exponential scale. For example, given a bidding vector with length 32, a binary format bidding vector can increase the bid upper bound from 32 to 232. However, previous protocols that use binary format bidding vectors require a somewhat homomorphic encryption (SHE) and a trusted manager. To make sure no party except the bidder itself knows its bid, our protocol does not have any managers. Instead, each bidder interacts with the Smart Contract independently. We propose a zero-knowledge proof that allows our protocol only requires partially homomorphic encryption such as an ElGamal encryption. To our best knowledge, our protocol is the first secureM+ 1st-price auction protocol that can reach an exponential bid upper bound without a manager and SHE.

Liqun Chen, Changyu Dong, Nada El Kassem, Christopher J. P. Newton · 5 authors

Direct Anonymous Attestation (DAA) was designed for the Trusted Platform Module (TPM) and versions using RSA and elliptic curve cryptography have been included in the TPM specifications and in ISO/IEC standards. These standardised DAA schemes have their security based on the factoring or discrete logarithm problems and are therefore insecure against quantum attackers. Research into quantum-resistant DAA has resulted in several lattice-based schemes. Now in this paper, we propose the first post-quantum DAA scheme from symmetric primitives. We make use of a hash-based signature scheme, which is a slight modification of SPHINCS+, as a DAA credential. A DAA signature, proving the possession of such a credential, is a multiparty computation-based non-interactive zero-knowledge proof. The security of our scheme is proved under the Universal Composability (UC) model. While maintaining all the security properties required for a DAA scheme, we try to make the TPM’s workload as low as possible. Our DAA scheme can handle a large group size (up to 2 60 group members), which meets the requirements of rapidly developing TPM applications.

Markulf Kohlweiss, Mahak Pancholi, Akira Takahashi

Most succinct arguments (SNARKs) are initially only proven knowledge sound (KS). We show that the commonly employed compilation strategy from polynomial interactive oracle proofs (PIOP) via polynomial commitments to knowledge sound SNARKS actually also achieves other desirable properties: weak unique response (WUR) and trapdoorless zero-knowledge (TLZK); and that together they imply simulation extractability (SIM-EXT). The factoring of SIM-EXT into KS + WUR + TLZK is becoming a cornerstone of the analysis of non-malleable SNARK systems. We show how to prove WUR and TLZK for PIOP compiled SNARKs under mild falsifiable assumptions on the polynomial commitment scheme. This means that the analysis of knowledge soundness from PIOP properties that inherently relies on non-falsifiable or idealized assumption such as the algebraic group model (AGM) or generic group model (GGM) need not be repeated. While the proof of WUR requires only mild assumptions on the PIOP, TLZK is a different matter. As perfectly hiding polynomial commitments sometimes come at a substantial performance premium, SNARK designers prefer to employ deterministic commitments with some leakage. This results in the need for a stronger zero-knowledge property for the PIOP. The modularity of our approach implies that any analysis improvements, e.g. in terms of tightness, credibility of the knowledge assumption and model of the KS analysis, or the precision of capturing real-world optimizations for TLZK also benefits the SIM-EXT guarantees.

Alex Kemloh Kouyem

Diese Arbeit präsentiert ein Protokoll für vertrauliche Transaktionen auf Ethereum, das auf einer kontenbasierten Struktur und Paillier-Verschlüsselung basiert. Die Integration von Non-Interactive Zero-Knowledge Range Proofs (NIZKRP) verbessert die Sicherheit. Die Implementierung und Tests auf Ethereum zeigen vergleichbare Transaktionskosten (Sicherheitsparameter 40) im Vergleich zu Protokollen mit Bulletproofs. Bei einem Sicherheitsparameter von 128 (NIZKRP-Empfehlung) ist das Protokoll jedoch nicht anwendbar. Die Arbeit betont die Effizienz und Wettbewerbsfähigkeit, hebt jedoch die Herausforderung bei höheren Sicherheitsparametern hervor. Das Protokoll bildet eine solide Grundlage, erfordert jedoch weitere Optimierungen für breitere Anwendbarkeit.

Maryam Sheikhi, Rosario Giustolisi, Carsten Schuermann

In 2016, Locher and Haenni (Locher andHaenni, 2016) proposed an e-voting scheme that offers verifiability, everlasting vote privacy, and computational receipt-freeness, as well as an informal discussion of how the scheme achieves such properties.We advance this line of work by proposing a new cryptographic scheme that provably satisfies those properties as well as everlasting participation privacy and efficient tallying.Receiptfreeness relies on deniable vote updating and verifiable null ballot posting, generated from public knowledge stored on the bulletin board.The everlasting vote and participation privacy properties directly result from the hash-based commitment scheme and efficient zero-knowledge proofs (SNARKs).Finally, we provide mathematical proofs for all the properties, including a new game-based definition of participation privacy.

M. Zhang, Yu Chen, Chuanzhou Yao, Zhichao Wang

No abstract is available for this record.

Ziqi Zhu, Kai Zhang, Junqing Gong, Haifeng Qian

No abstract is available for this record.

Dmitry Khovratovich, Mario Marhuenda Beltrán, Bart Mennink

No abstract is available for this record.

Xiangyu Su, Mario Larangeira, Keisuke Tanaka

Proof-of-useful-work (PoUW), an alternative to the widely used proof-of-work (PoW), aims to re-purpose the network’s computing power. Namely, users evaluate meaningful computational problems, e.g., solving optimization problems, instead of computing numerous hash function values as in PoW. A recent approach utilizes the training process of deep learning as “useful work”. However, these works lack security analysis when deploying them with blockchain-based protocols, let alone the informal and over-complicated system design. This work proposes a distributed proof-of-deep-learning (D-PoDL) scheme concerning PoUW’s requirements. With a novel hash-traininßg-hash structure and model-referencing mechanism, our scheme is the first deep learning-based PoUW scheme that enables achieving better accuracy distributively. Next, we introduce a transformation from the D-PoDL scheme to a generic D-PoDL blockchain protocol which can be instantiated with two chain selection rules, i.e., the longest-chain rule and the weight-based blockchain framework (LatinCrypt’ 21). This work is the first to provide formal proofs for deep learning-involved blockchain protocols concerning the robust ledger properties, i.e., chain growth, chain quality, and common prefix. Finally, we implement the D-PoDL scheme to discuss the effectiveness of our design.

Lennart Braun, Ivan Damgård, Claudio Orlandi

We construct the first actively-secure threshold version of the cryptosystem based on class groups from the so-called CL framework (Castagnos and Laguillaumie, 2015). We show how to use our threshold scheme to achieve general universally composable (UC) secure multiparty computation (MPC) with only transparent set-up, i.e., with no secret trapdoors involved. On the way to our goal, we design new zero-knowledge (ZK) protocols with constant communication complexity for proving multiplicative relations between encrypted values. This allows us to use the ZK proofs to achieve MPC with active security with only a constant factor overhead. Finally, we adapt our protocol for the so called “You-Only-Speak-Once” (YOSO) setting, which is a very promising recent approach for performing MPC over a blockchain. This is possible because our key generation protocol is simpler and requires significantly less interaction compared to previous approaches: in particular, our new key generation protocol allows the adversary to bias the public key, but we show that this has no impact on the security of the resulting cryptosystem.

Johannes Blömer, Jan Bobolz, Laurens Porzenheim

No abstract is available for this record.

Alex Ozdemir, Riad S. Wahby, Fraser Brown, Clark Barrett

Abstract Zero Knowledge Proofs (ZKPs) are cryptographic protocols by which a prover convinces a verifier of the truth of a statement without revealing any other information. Typically, statements are expressed in a high-level language and then compiled to a low-level representation on which the ZKP operates. Thus, a bug in a ZKP compiler can compromise the statement that the ZK proof is supposed to establish. This paper takes a step towards ZKP compiler correctness by partially verifying a field-blasting compiler pass, a pass that translates Boolean and bit-vector logic into equivalent operations in a finite field. First, we define correctness for field-blasters and ZKP compilers more generally. Next, we describe the specific field-blaster using a set of encoding rules and define verification conditions for individual rules. Finally, we connect the rules and the correctness definition by showing that if our verification conditions hold, the field-blaster is correct. We have implemented our approach in the CirC ZKP compiler and have proved bounded versions of the corresponding verification conditions. We show that our partially verified field-blaster does not hurt the performance of the compiler or its output; we also report on four bugs uncovered during verification.

Jayamine Alupotha

Decentralized identities return control of identities to the identity owners. Although current work enhances the privacy of these publicly stored identities using encryption and zero-knowledge proofs, decentralized identities can still be abused due to the following problems: identity holders, e.g., blockchain peers, can profile identity owners by looking at “who is reading which identity data”, and identity verifiers, e.g., applications and websites, learn private data about owners, like their monetary values and previous transactions during the identity linking. In the worst case scenario, the identity holders and verifiers collaboratively profile users to learn more information. As a practical solution, we introduce the notion of Double Blind Proofs of Existence (DBPoE), which shows that an opened DID is committed in one of the constant-sized multi-generator Pedersen commitments (33 Bytes at 128-bit security), and nothing else. Hence, our DBPoE double-blinds identity holders and identity verifiers to mitigate private information leakage. Equally importantly, our multi-generator commitment-based DBPoE is more resistant to graph analysis than other one-of-many proofs, e.g., ring signatures, which we show mathematically using the maximal flow problem. Our DBPoE protocol has a size complexity ofO(log2(N) +m) when the real commitment is hidden inNcommitments andmgenerators are used, e.g., whenm= 4, a DBPoE of 1000 commitments is only 3 KB.

Chaya Ganesh, Yashvanth Kondi, Claudio Orlandi, Mahak Pancholi · 6 authors

Zero-knowledge Succinct Non-interactive ARguments of Knowledge (zkSNARKs) are becoming an increasingly fundamental tool in many real-world applications where the proof compactness is of the utmost importance, including blockchains. A proof of security for SNARKs in the Universal Composability (UC) framework (Canetti, FOCS’01) would rule out devastating malleability attacks. To retain security of SNARKs in the UC model, one must show their simulation-extractability such that the knowledge extractor is both black-box and straight-line , which would imply that proofs generated by honest provers are non-malleable . However, existing simulation-extractability results on SNARKs either lack some of these properties, or alternatively have to sacrifice witness succinctness to prove UC security. In this paper, we provide a compiler lifting any simulation-extractable NIZKAoK into a UC-secure one in the global random oracle model, importantly, while preserving the same level of witness succinctness. Combining this with existing zkSNARKs, we achieve, to the best of our knowledge, the first zkSNARKs simultaneously achieving UC-security and constant sized proofs.

Carlos Aguilar-Melchor, Nicolas Gama, James Howe, Andreas Hülsing · 6 authors

No abstract is available for this record.

Komal Manohar Tekale, Nivedita Rahul

In this paper, a model is presented in the operational form of blockchain and smart contract utilization to modernise insurance claims settlement, which is enterprise-ready. Design a permissioned, Ethereum-compatible ledger that encodes policy terms limits, deductibles, exclusions and orchestrates deterministic claim state transitions from First Notice of Loss (FNOL) to payout. Off-chain storage stores sensitive artifacts (PII/PHI, images, medical records) encrypted in vaults, and on-chain records append cryptographic digests and events that can be audited by tampering evidence. This is provided by evidence (in the form of signed oracles, such as weather indices, hospital discharge summaries, police reports), and permits parametric claims to be settled quickly and routine indemnity claims to undergo high straight-through processing (STP) with human attention reserved to exceptions. The methodology emphasizes formal assurance (static analysis, property-based tests, optional formal verification), runtime safety (circuit breakers, timelocked upgrades), and robust key/oracle governance. Pilot testing in pilot testing, the methodology provides a shorter cycle time, less reconciliation, and quantifiable mitigation of fraud-leakage but still ensures regulatory compliance by selective disclosure and privacy-by-design. Also work through the dynamics of constraints throughput and fee dynamics, legal enforceability, legacy interoperability, and privacy-versus-transparency trade-off and a roadmap of staged adoption, starting with low-dispute, oracle-rich products, then triage, partial advances, and subrogation workflows. Findings indicate that blockchain is likely to be the most useful as a coordination/assurance layer to supplement, but not to substitute, fundamental insurance infrastructure

Miaomiao Wang, Lanlan Rui, Siya Xu, Zhipeng Gao · 6 authors

No abstract is available for this record.