Pierpaolo Della Monica, Ivan Visconti, Andrea Vitaletti, Marco Zecchini
An essential requirement for the large-scale adoption of Web3 is enabling users to benefit from their data even within already deployed systems. This raises an important open question: how can existing, widely adopted software verify that a user has retrieved specific data from a TLS server? Impressive scientific results (e.g., DECO [CCS20] and the work of Xie et al. [USENIX24]) and industrial products (TLSNotary) have recently made progress in the above challenging direction. However, while they nicely leave TLS servers untouched, the retrieved data is then used in computations with verifiers that are required to run some advanced non-standardized cryptographic schemes (e.g., ZK-SNARKs), which clearly limits the large-scale adoption of the proposed technologies. In this paper, building on top of previous approaches and relying on the recent concept of Predicate Blind Signatures of Fuchsbauer and Wolf [Eurocrypt24], we bypass the limits of prior work by presenting ACTS a distributed architecture that, while still leaving TLS servers untouched, it allows a user to show possession of data retrieved from TLS servers simply requiring that the software of the verifier can check a standard signature. Our contributions include a round-optimal predicate blind signature protocol that produces standard RSA-PSS signatures. We show how this primitive can be integrated into the DECO architecture (and its successors) to certify data retrieved from TLS servers. Furthermore, we have optimized our construction to make it practical on commodity hardware for a large and significant class of policies implemented by the notary (i.e., the actor that is in charge of obliviously certifying TLS data, therefore preserving data confidentiality). We provide an experimental evaluation on the simple but powerful enough use case of a PDF document downloaded from a TLS server and encoded into an AES-GCM ciphertext. The user will then get a certified PDF through a standard PADES signature added obliviously to the PDF along with some metadata by a notary service. The resulting standard signed PDF document can be transparently verified using off-the-shelf PDF readers. Our experimental validation demonstrates that our architecture is suitable for real-world deployment in concrete scenarios.
Long-range attacks pose a significant threat to the integrity of Proof-of-Stake (PoS) blockchains by enabling adversaries to reconstruct an alternative chain history embedded with fraudulent transactions. These attacks can deceive honest participants into accepting a maliciously crafted branch as the canonical chain. While Key Evolving Signature (KES) schemes are widely adopted to mitigate such threats, they typically rely on the assumption that validators behave honestly. In this work, we challenge this assumption by demonstrating how a malicious validator can exploit inherent limitations in existing KES-based mechanisms to mount a successful long-range attack. To address this critical vulnerability, we introduce a novel cryptographic construction that combines one-time signatures with commitment schemes. Our approach imposes constraints on the signing capabilities of validators, thereby significantly reducing the feasibility of long-range attacks. We provide rigorous formal security proofs to substantiate the robustness of our scheme and conduct a comprehensive performance evaluation. The results show that our solution is both computationally and storage efficient, making it a practical and scalable defense mechanism for real-world PoS blockchain deployments.
Isaac Amankona Obiri, Qi Xia, Jianbin Gao, Hu Xia · 5 authors
The growing adoption of electronic personal health records (ePHRs) demands cryptographic solutions that ensure secure and efficient data access. Threshold cryptography provides a framework for controlled multi-party access, yet existing schemes face practical limitations. Many require trusted key dealers, creating single points of failure and key escrow vulnerabilities, while others rely on pairing-based constructions that scale poorly. Furthermore, batch-oriented processing in previous schemes fails to support individual on-demand access patterns typical in healthcare applications. We propose a Distributed Identity-Based Threshold Decryption (DIBTD) scheme that addresses these limitations. First, our protocol removes all trusted setup assumptions through a fully distributed key generation mechanism based on verifiable secret sharing. Second, it achieves constant-time encryption and decryption operations, independent of committee size, by using efficient elliptic curve operations on secp256k1 rather than computationally heavy pairings, yielding up to 56× faster encryption than prior work. Third, DIBTD integrates the detection of malicious actors via zero-knowledge proofs, allowing the dynamic exclusion of compromised participants during system initialization. We provide formal security proofs showing the security of IND-CCA2 in the random oracle model under the discrete logarithm of the elliptic curve (ECDLP) and computational Diffie-Hellman (CDH) assumptions. The scheme remains secure against adaptive adversaries that control up to$t-1$participants. Experimental evaluation demonstrates practical efficiency: ciphertexts of only 86 bytes, constant 33-byte public keys, and sub-millisecond encryption latency. A pure Rust implementation on commodity hardware achieves 0.065ms per patient record while maintaining 128-bit security.
Blockchain technology enables tamper-resistant and transparent data management, but it continues to face pressing challenges related to security and performance. Existing blockchain applications predominantly rely on software-based implementations, which are susceptible to side-channel analysis (SCA) attacks and constrained by the limited efficiency of general-purpose processors. This thesis addresses these challenges by leveraging Field-Programmable Gate Array (FPGA) technology to develop hardware-based solutions that strengthen cryptographic security and accelerate blockchain execution. Three major hardware contributions are presented: an Ethereum hardware wallet resistant to SCA, a hybrid Ethereum–Bitcoin hardware wallet supporting both Hierarchical Deterministic (HD) and Non-Deterministic (ND) modes, and a hardware-accelerated Ethereum Virtual Machine (EVM). The first contribution, EthVault, introduces the first complete hardware architecture of an Ethereum HD cold wallet and its FPGA implementation. EthVault integrates a side-channel resistant elliptic curve cryptography (ECC) design, the first hardware realization of the child key derivation (CKD) function, and resource-conscious implementations of key cryptographic algorithms, including ECDSA, HMAC-SHA-512, PBKDF2, SECP256K1, elliptic curve point operations, and the Ethereum checksum algorithm, resulting in a secure, compact wallet. The second contribution, HardVault, presents the first FPGA-based hybrid Ethereum–Bitcoin cold wallet architecture. Supporting both HD and ND key generation methods, HardVault improves resource efficiency by reusing cryptographic primitives common to Ethereum and Bitcoin, including RIPEMD-160, CKD, and SHA-256. This reuse minimizes hardware overhead, enabling a lightweight and energy-efficient solution. A detailed power–performance evaluation further demonstrates HardVault’s superior efficiency, with measurable improvements over commercial wallets such as Trezor One. The third contribution, EVMx, proposes a single-core FPGA-based EVM that offloads smart contract execution from full and archival nodes to a dedicated hardware accelerator. EVMx preserves full compatibility with the EVM’s stack-based semantics while introducing performance optimizations such as lightweight pipelining, simplified opcode decoding, dynamic corner-case handling, and selective parallelism. Experimental results show significant speedups for both individual opcodes and complete smart contract execution compared to CPU-based and prior FPGA designs. Furthermore, integration strategies are discussed to enable scalable adoption of EVMx within existing Ethereum clients. Overall, this thesis demonstrates that FPGA-based designs can substantially strengthen blockchain ecosystems by enhancing both security (EthVault and HardVault) and computational performance (EVMx), thereby paving the way for more secure, efficient, and practical blockchain deployments.
Cryptographic Implementations and Security
Cryptography and Residue Arithmetic
Physical Unclonable Functions (PUFs) and Hardware Security
Blockchain deployments continue to face challenges related to scalability, energy consumption, and susceptibility of classical cryptographic primitives to emerging quantum attacks. Conventional systems employing RSA or DSA signatures and consensus mechanisms such as Proof of Work (PoW) or Proof of Stake (PoS) incur substantial computational overhead and are not well suited for cloud-scale execution. This study presents PQ-PoETChain, a post-quantum-secure blockchain model integrating NTRU-based signatures, an adaptive Proof of Elapsed Time (PoET) protocol executed within Trusted Execution Environments (TEEs), and a Lightweight Hash Validation (LHV) mechanism. The framework was implemented in Python and evaluated in a controlled simulation environment using 50-1000 nodes, with repeated trials to measure variability across throughput, latency, and energy metrics. NTRU demonstrated sub-2 ms signature operations, while the adaptive PoET configuration reduced consensus delay under load-dependent conditions. Across multiple experimental runs, the system achieved an average throughput of ~ 195 TPS with a latency of 189 ± 4 ms at 500 nodes. Energy consumption reduced by up to 91.8% (± 1.6%) when compared with PoW under identical conditions. LHV further lowered verification cost by replacing Merkle-tree traversal with constant-time hash-pointer validation. Results indicate that PQ-PoETChain offers a balanced combination of quantum-resilient security and improved performance characteristics suitable for cloud-native and large-scale deployments.
Maiesha Fahomida, Nushraq Nawer Hossain, Farhan Ahmad Nafis, Raian Islam
Modern digital communication requires stronger mechanisms for both confidentiality and authentication to mitigate threats such as impersonation, replay, and eavesdropping. Although traditional cryptographic methods offer secrecy, they lack strong identity verification in adversarial environments. To ensure security in both transmission and authentication, we proposed a hybrid framework combining the most effective mechanisms for secure communication, enhanced with LSB Steganography to conceal sensitive information. Zero-knowledge proofs are used for secure authentication. Diffie-Hellman with AES-256-GCM ensures confidentiality and data integrity, while LSB Steganography provides secure concealment of transmitted communication. Our method has been evaluated using a variety of techniques, including steganographic quality assessment, encryption-decryption performance testing, and authentication time measurement, confirming its resilience against common security risks. The proposed methods achieve PSNR values up to$\mathbf{7 4. 5 8 ~ d B}$and SSIM of 0.9999. The encryption time ranges from 0.035 ms to 0.068 ms, while the decryption time remains consistently lower, ranging from 0.008 ms to 0.015 ms. The results demonstrate that the proposed framework is a viable option for secure data transfer, as it guarantees confidentiality, integrity, authentication, and covert communication.
This paper presents zero knowledge proofs, their cryptographic significance and applications. It presents a basic classification: interactive and noninteractive zero knowledge proofs. It presents and compares three protocols of non-interactive zero knowledge proofs: ZK-SNARK, ZK-STARK and Bulletproofs. It presents the quadratic residue problem and proofs it with both interactive and non-interactive zero knowledge proofs. The non-interactive protocol used to prove the quadratic residue problem is ZK-SNARK. The proof is implemented in the Python programming language, using python-snark library.
Ghassan Samara, Ibrahim Obeidat, Mais Haj Qasem, Raed Alazaidah · 9 authors
Vehicular networks must authenticate high-rate safety messages under tight latency while preserving privacy and remaining secure against post-quantum adversaries. We present$P Q$-Rate, a post-quantum, privacy-preserving, rate-limited credential system for C-V2X. PQ-Rate replaces per-message signatures with a one-round-trip (1-RTT) KEM handshake to derive an AEAD session key, keeping the fast path lightweight. Vehicles obtain unlinkable Rate-Limited Anonymous Tokens (RLATs) from edge issuers (RSU/MEC) via a threshold VOPRF; each token is spent once using a zero-knowledge proof that binds a unique nullifier, enforcing per-epoch budgets without revealing identity. Revocation scales via compact, signed Bloom-filter digests broadcast by RSUs, with optional online disambiguation to handle rare false positives, and accountability is provided by threshold opening of verifiably encrypted token metadata. We prototype PQ-Rate in NS-3 with SUMO-driven mobility and compare against pseudonym-based PKI and verifier-local-revocation group signatures. Metrics include 1-RTT authentication latency, beacon delivery ratio (PDR), channel busy ratio (CBR), verifier throughput, revocation-wire overhead, and realized Sybil capacity. Results show that PQ-Rate maintains sub- 20 ms session setup, improves PDR under high density by reducing airtime overhead, increases verifier throughput via batching and inexpensive decapsulation, and bounds attacker identities to the product of enrolled hardware modules and budget. Revocation digests remain small (on the order of 9-12 KB for thousands of inserts at$10^{-3}-10^{-4}$false-positive targets), supporting frequent broadcast without inflating CBR. PQ-Rate demonstrates that post-quantum security, strong privacy, Sybil resistance, and rapid revocation can be achieved simultaneously within V2X timing constraints.
Cryptographic Implementations and Security
Physical Unclonable Functions (PUFs) and Hardware Security
This work introduces the Adversarial Cost Model (ACM v1.0), a formal security framework unifying computational, economic, and physical attack costs in a single rational adversary model. Unlike traditional security models based purely on computational hardness, ACM evaluates real-world feasibility of attacks under post-quantum cryptography, behavioral authentication, zero-knowledge proof systems, and decentralized governance. The model formalizes adversarial actions through total cost functions combining time complexity, hardware requirements, capital liquidity, and physical laboratory constraints. Multiple critical attack classes are analyzed, including hybrid side-channel + Grover attacks, GAN-based behavioral cloning, flash-loan Sybil governance attacks, post-quantum brute-force exhaustion, and zero-knowledge proof forgery. The results demonstrate that many real-world system failures arise not from cryptographic weakness, but from mispriced economic atomicity and cost-free identity or governance acquisition. ACM provides a rationality threshold theorem formalizing when attacks become economically and physically irrational. The model directly informs secure system architecture design by enforcing multi-layer cost escalation across cryptographic, physical, behavioral, and governance layers. This work is intended for cryptography, blockchain security, adversarial machine learning, economic attack modeling, and post-quantum system design.
Open access
Cryptographic Implementations and Security
Smart Grid Security and Resilience
Physical Unclonable Functions (PUFs) and Hardware Security
This work introduces the Adversarial Cost Model (ACM v1.0), a formal security framework unifying computational, economic, and physical attack costs in a single rational adversary model. Unlike traditional security models based purely on computational hardness, ACM evaluates real-world feasibility of attacks under post-quantum cryptography, behavioral authentication, zero-knowledge proof systems, and decentralized governance. The model formalizes adversarial actions through total cost functions combining time complexity, hardware requirements, capital liquidity, and physical laboratory constraints. Multiple critical attack classes are analyzed, including hybrid side-channel + Grover attacks, GAN-based behavioral cloning, flash-loan Sybil governance attacks, post-quantum brute-force exhaustion, and zero-knowledge proof forgery. The results demonstrate that many real-world system failures arise not from cryptographic weakness, but from mispriced economic atomicity and cost-free identity or governance acquisition. ACM provides a rationality threshold theorem formalizing when attacks become economically and physically irrational. The model directly informs secure system architecture design by enforcing multi-layer cost escalation across cryptographic, physical, behavioral, and governance layers. This work is intended for cryptography, blockchain security, adversarial machine learning, economic attack modeling, and post-quantum system design.
Open access
2 source records
Cryptographic Implementations and Security
Smart Grid Security and Resilience
Physical Unclonable Functions (PUFs) and Hardware Security
This publication introduces Zero-Knowledge Behavioral Proof (ZKBP) as a post-biometric authentication primitive designed for the QADMON canonical security framework. ZKBP replaces traditional biometric and password-based identity with cryptographically verifiable behavioral continuity. The protocol proves liveness, integrity and continuity of behavior without revealing biometric templates, raw behavioral signals, or any permanent human identifier. The package includes: - Formal cryptographic definition of ZKBP - Security proofs under LWE-based post-quantum assumptions - Comprehensive threat model (AI imitation, replay, side-channels, insider threats) - Protocol specification in JSON - Comparative security tables (CSV) - Multilingual human-readable documentation (EN, RU, HE, ZH, AR) - Implementation notes for PQC + TEE environments This module follows the canonical QADMON axiom: FSIG ≠ Cryptographic Key FSIG = Zero-Knowledge Behavioral Proof The only cryptographic secret is a post-quantum key stored inside a Trusted Execution Environment (TEE). This work is published as Module 02 of the QADMON Canonical Security Framework.
We present ZK IR, a novel 32-bit instruction set architecture (ISA) specifically designed for efficient zero-knowledge proof generation using STARK protocols. Unlike existing zkVMs that adapt general-purpose ISAs like RISC-V, ZK IR is designed from first principles to minimize proving overhead while maintaining compatibility with modern compiler toolchains. Our key contribution is a rigorous analysis demonstrating that a pure 32-bit register architecture with software-based multi-precision arithmetic outperforms designs with wider registers or specialized field arithmetic units. We achieve approximately 2× reduction in constraint count compared to naive approaches. ZK IR uses the Baby Bear field (31-bit prime) with Plonky3 for proving, and provides an LLVM-based compiler infrastructure enabling developers to write ZK applications in Rust, C, and C++.
Hikaru Okamoto, Vu Trung Duong Le, Hoai Luan Pham, Van Tinh Nguyen · 5 authors
Zero-Knowledge Proof (ZKP) is a privacy-preserving protocol that allows a prover to demonstrate the validity of a statement without revealing its details. A widely used primitive of ZKP, Zero-Knowledge Succinct Non-Interactive Argument of Knowledge (zk-SNARK), has attracted significant attention in edge computing; however, edge devices face severe resource constraints when processing its computational bottleneck, Montgomery multiplication. This paper proposes MMzk, a lightweight hardware architecture optimized for 384-bit Coarsely Integrated Operand Scanning (CIOS) Montgomery multiplication, which is primarily employed in multi-scalar multiplication (MSM) of zk-SNARKs. To achieve both high performance and resource efficiency, MMzk core operating at the System-on-Chip (SoC) level integrates three key optimizations: resource sharing of two adders, a subtractor, and a multiplier; effective memory organization for large-data processing; and double-buffering memory scheduling. Implementation results on a Xilinx ZCU102 SoC show that MMzk core operates at up to 250MHz with a utilization of 3,590 LUTs, 1,648 FFs, 16 DSPs, and 6 BRAM36 blocks. Compared with existing FPGA-based counterparts, it achieves a throughput of 657.53Mbps (up to 35.9 times higher) and an area efficiency of 81.48Kbps/eLUT (up to 9.5 times higher). Furthermore, real-time evaluation demonstrates an energy efficiency of 9,030Mbps/W at 250MHz and 67mW, surpassing modern CPUs by up to 52.9 times. These results confirm MMzk core as an energy-efficient and high-performance solution for zk-SNARK-based blockchain systems and other Montgomery multiplication applications.
Provable security is a cornerstone of modern cryptography: Due to ubiquitous and diverse applications of cryptography, a proof of security gives us the necessary confidence to deploy a cryptographic protocol. In most cases, such a security proof comes in the form of a black-box reduction, which bases the security of a potentially complex protocol on a small set of simple and abstract assumptions that are much easier to analyse. However, proving a black-box reduction can be quite complicated, and we do not have proofs for every protocol used in practice. Here, analysing the protocols relative to oracles, a technique from computational complexity theory, can provide insights: Oracles provide the ability to compute functionalities in one computational step that otherwise might not be efficiently computable, e.g., provide access to a truly random function or solve any NP-complete problem. These oracles now allow us to replace some parts in the protocol with abstract, idealized primitives that are easier to analyse, e.g., to replace a one-way function with a truly random function. In this thesis, we utilize oracles in two different ways. In the first part, we use oracles to prove lower bounds for cryptographic primitives, i.e., showing that certain assumptions are not sufficient to build this primitive securely. The essential idea here, going back to Impagliazzo and Rudich, is to replace the assumption with an oracle, i.e., replacing a one-way function with a truly random function, and then showing that relative to this oracle, it is impossible to build the primitive. From this impossibility result relative to the oracle, we can now conclude that the primitive cannot be built from the assumption in a black-box way. We use this technique to prove a lower bound on the efficiency of constructing strong from weak one-way functions, to show that we cannot construct collision-resistant hash functions from distributional collision-resistant hash functions in a fully black-box way, and to prove that extremely lossy functions cannot be built from a large class of symmetric primitives in a black-box way. In the second part of this thesis, we use oracles as idealized models that can be used to provide heuristic security arguments for protocols.These idealized models, starting with the random oracle model (short ROM) introduced and defined by Fiat and Shamir as well as Bellare and Rogaway, were motivated by the existence of very efficient cryptographic protocols used in practice, but for which no proof of security existed. Using idealized models, it was now possible to give at least a heuristic security argument for them. In this thesis, we first focus on the common random string model, an idealized model introduced to circumvent impossibility results for non-interactive zero-knowledge proofs. We show how to reuse a single common random string for polynomially many non-interactive statistical zero-knowledge arguments, as well as analyze the relation between different soundness definitions used in literature. In a second result, we introduce an alternative notion for the ROM, the universal random oracle model, which brings this idealized model closer to reality.
Verifiable Random Functions (VRFs) and Oblivious Pseudorandom Functions (OPRFs) are essential cryptographic primitives in privacy-preserving applications such as anonymous authentication, private set intersection (PSI), and decentralized identity. Existing constructions, however, rely on number-theoretic assumptions that are vulnerable to quantum attacks. This PhD research project focuses on constructing efficient and practical VRFs and OPRFs from lattice-based assumptions to ensure post-quantum security. A key obstacle in these constructions is the overhead of zero-knowledge proofs (ZKPs), particularly range proofs, which are costly in terms of size and prover complexity. To address this, we investigate probabilistic techniques that relax exact correctness. In particular, we explore approximate range proofs and algebraic transformations, such as using automorphisms in polynomial rings to simulate inner product arguments via polynomial multiplication. These methods enable more efficient and scalable lattice-based constructions of VRFs, including group and context-bound variants, as well as OPRFs. The goal is to make these primitives practical for deployment in post-quantum privacy-preserving systems.
This work proves a formal impossibility theorem stating that no observable behavioral or biometric signal can serve as a cryptographic secret under standard semantic security notions (IND-CPA / IND-CCA), in any computational model admitting machine learning approximation and side-channel observability. The result holds in classical, post-quantum, and hybrid adversarial models. We further derive strict architectural consequences for biometric authentication, fuzzy extractors, and behavioral identification systems, showing that such signals may only function as zero-knowledge liveness proofs, not as entropy sources for cryptographic key material.
Sangwon Shin, Ngoc-Son Pham, Lei Xu, Weidong Shi · 5 authors
Zero-Knowledge Proof (ZKP) cryptographic algorithms have garnered significant attention for their ability to enhance privacy. However, the practical deployment of these algorithms remains challenging because they demand extremely high computational effort and handle huge volumes of data, especially in the Number Theoretic Transform (NTT) step. In this work, we propose an HBM-aware dataflow that employs sub-tiling and row-shuffling techniques to overcome the nonuniform stride access problem and to maximize HBM bandwidth utilization. We also design the NTT accelerator to use minimal FPGA resources. In particular, we explore diverse design options for the 256-bit modular multiplier and adopt an efficient design that optimizes resource usage and performance. Experimental results demonstrate that the proposed accelerator achieves lower latency and enhanced resource utilization compared to state-of-the-art FPGA-based designs.
Abstract — The Fractal Eavesdrop Detection (FED) protocol defines a cryptographic mutual-authentication... The Fractal Eavesdrop Detection (FED) protocol defines a cryptographic mutual-authentication and integrity validation mechanism between two fractal nodes sharing a recursive lineage. Unlike conventional systems that rely on fixed keys or static hashes, FED uses algorithmic mutability, session-based seed derivation, multi-point challenge validation, and time-bound CRC binding to detect both impersonation and passive eavesdropping. The protocol is designed for lightweight, low-power devices such as ESP32-class microcontrollers and operates without blockchain consensus or zero-knowledge proofs, while still enabling secure proof-of-origin and tamper-awareness. FED serves as the security and validation layer within the EQUORA Institute’s Fractal Economy architecture and complements the BlockFractal cryptographic tokenization layer and the EquoraVault hardware-based proof-of-impact system. This document is released as part of the EQUORA Institute White Paper Series and is a preprint version (v0.8), subject to revision. All versions remain archived for DOI-based citation integrity.
Open access
2 source records
Chaos-based Image/Signal Encryption
Physical Unclonable Functions (PUFs) and Hardware Security