Cryptography and Security · Cross-listed from q-fin.MF
A Formal Approach to AMM Fee Mechanisms with Lean 4
Marco Dessalvi, Massimo Bartoletti and Alberto Lluch-Lafuente
Decentralized Finance (DeFi) has revolutionized financial
markets by enabling complex asset-exchange protocols without trusted intermediaries. Automated
Market Makers (AMMs) are a central component of DeFi, providing the core functionality of swapping assets of different types at algorithmically computed exchange rates. Several mainstream AMM implementations are based on the constant-product model, which ensures that swaps preserve the product of the
token reserves in the AMM – up to a trading fee used to incentivize liquidity provision. Trading fees substantially complicate the economic properties of AMMs, and for this reason some AMM models abstract them away in order to simplify the analysis. However, trading fees have a non-trivial impact on users' trading strategies, making it crucial to develop refined AMM models that precisely account for their effects. We extend a foundational model of AMMs by introducing a new parameter, the trading fee $\phi\in(0,1]$, into the swap rate function. Fee amounts increase inversely proportional to $\phi$. When $\phi = 1$, no fee is applied and the original model is recovered. We analyze the resulting fee-adjusted model from an economic perspective. We show that several key properties of the swap rate function, including output-boundedness and monotonicity, are preserved. At the same time, other properties - most notably additivity - no longer hold. We precisely characterize this deviation by deriving a generalized form of additivity that captures the effect of swaps in the presence of trading fees. We prove that when $\phi < 1$, executing a single large swap yields strictly greater profit than splitting the trade into smaller ones. Finally, we derive a closed-form solution to the arbitrage problem in the presence of trading fees and prove its uniqueness. All results are formalized and machine-checked in the Lean 4 proof assistant.
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Cryptography and Security
Reconstructing Protected Biometric Templates from Binary Authentication Results
Eliron Rahimi, Margarita Osadchy and Orr Dunkelman
Biometric data is considered to be very private and highly sensitive. As such, many methods for biometric template protection were considered over the years – from biohashing and specially crafted feature extraction procedures, to the use of cryptographic solutions such as Fuzzy Commitments or the use of Fully Homomorphic Encryption (FHE). A key question that arises is how much protection these solutions can offer when the adversary can inject samples, and observe the outputs of the system. While for systems that return the similarity score, one can use attacks such as hill-climbing, for systems where the adversary can only learn whether the authentication attempt was successful, this question remained open. In this paper, we show that it is indeed possible to reconstruct the biometric template by just observing the success/failure of the authentication attempt (given the ability to inject a sufficient amount of templates). Our attack achieves negligible template reconstruction loss and enables full recovery of facial images through a generative inversion method, forming a pipeline from binary scores to high-resolution facial images that successfully pass the system more than 98% of the time. Our results, of course, are applicable for any protection mechanism that maintains the accuracy of the recognition.
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Cryptography and Security · Cross-listed from cs.CL
Improving User Privacy in Personalized Generation: Client-Side Retrieval-Augmented Modification of Server-Side Generated Speculations
Alireza Salemi and Hamed Zamani
Personalization is crucial for aligning Large
Language Model (LLM) outputs with individual user preferences and background knowledge. State-of-the-art solutions are based on
retrieval augmentation, where relevant context from a user profile is retrieved for LLM consumption. These methods deal with a trade-off between exposing retrieved private data to cloud providers and relying on less capable local models. We introduce $P^3$, an interactive framework for high-quality personalization without revealing private profiles to server-side LLMs. In $P^3$, a large server-side model generates a sequence of $k$ draft
tokens based solely on the user query, while a small client-side model, with
retrieval access to the user's private profile, evaluates and modifies these drafts to better reflect user preferences. This process repeats until an end
token is generated. Experiments on LaMP-QA, a recent
benchmark consisting of three personalized question answering
datasets, show that $P^3$ consistently outperforms both non-personalized server-side and personalized client-side baselines, achieving statistically significant improvements of $7.4%$ to $9%$ on average. Importantly, $P^3$ recovers $90.3%$ to $95.7%$ of the utility of a “leaky” upper-bound scenario in which the full profile is exposed to the large server-side model.
Privacy analyses, including linkability and attribute inference attacks, indicate that $P^3$ preserves the
privacy of a non-personalized server-side model, introducing only marginal additional leakage ($1.5%$–$3.5%$) compared to submitting a query without any personal context. Additionally, the framework is efficient for edge deployment, with the client-side model generating only $9.2%$ of the total
tokens. These results demonstrate that $P^3$ provides a practical, effective solution for personalized generation with improved
privacy.
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Cryptography and Security
Private Iris Recognition with High-Performance FHE
Jincheol Ha, Guillaume Hanrot, Taeyeong Noh et al. (+3 more)
Among biometric verification systems, irises stand out because they offer high accuracy even in large-scale databases. For example, the World ID project aims to provide authentication to all humans via iris recognition, with millions already registered. Storing such biometric data raises
privacy concerns, which can be addressed using
privacy-enhancing techniques. Bloemen et al. describe a solution based on 2-out-of-3 Secret-Sharing Multiparty Computation (SS-MPC), for the World ID setup. In terms of security, unless an adversary corrupts 2~servers, the iris codes remain confidential and nothing leaks beyond the result of the computation. Their solution is able to match~$32$ users against a database of~$2^{22}$ iris codes in~$\approx 2$s , using~24 H100 GPUs, more than 40~communication rounds and $81$GB/party of data transferred (the timing assumes a network speed above~3Tb/s). In the present work, we explore the use of Threshold Fully Homomorphic Encryption (ThFHE) for the same task. The ThFHE solution brings a number of security advantages: no trusted setup, the encrypted database and queries can be public, the secret can be distributed among many parties, and active security can be added without significant performance degradation. Our proof-of-concept implementation of the computation phase handles $32$~eyes against a database of $7\cdot 2^{14}$ iris codes in~$\approx 1.8$s ($\approx 0.33s$ for 4 eyes against the same database), using 8 RTX-5090 GPUs. To this, one should add~2 to 3 rounds of communication (depending on deployment choice). We perform the matching using the CKKS (Th)FHE scheme. Our main technical ingredients are the use of recent progress on FHE-based linear
algebra boosted using int8 GPU operations, and the introduction of a technique reducing the number of ciphertexts to be processed as early as possible.
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All authors Jincheol Ha, Guillaume Hanrot, Taeyeong Noh, Jung Hee Cheon, Jung Woo Kim, Damien Stehlé
Cryptography and Security
Breaking the Protocol: Security Analysis of the Model Context Protocol Specification and Prompt Injection Vulnerabilities in Tool-Integrated LLM Agents
Narek Maloyan and Dmitry Namiot
The Model Context Protocol (MCP) has emerged as a de facto standard for integrating Large
Language Models with external tools, yet no formal security analysis of the protocol specification exists. We present the first rigorous security analysis of MCP's architectural design, identifying three fundamental protocol-level vulnerabilities: (1) absence of capability attestation allowing servers to claim arbitrary permissions, (2) bidirectional sampling without origin authentication enabling server-side
prompt injection, and (3) implicit trust propagation in multi-server configurations. We implement MCPBench, a novel framework bridging existing
agent security
benchmarks to MCP-compliant infrastructure, enabling direct measurement of protocol-specific attack surfaces. Through controlled experiments on 847 attack scenarios across five MCP server implementations, we demonstrate that MCP's architectural choices amplify attack success rates by 23–41% compared to equivalent non-MCP integrations. We propose MCPSec, a backward-compatible protocol extension adding capability attestation and message authentication, reducing attack success rates from 52.8% to 12.4% with median latency overhead of 8.3ms per message. Our findings establish that MCP's security weaknesses are architectural rather than implementation-specific, requiring protocol-level remediation.
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Cryptography and Security
Prompt Injection Attacks on Agentic Coding Assistants: A Systematic Analysis of Vulnerabilities in Skills, Tools, and Protocol Ecosystems
Narek Maloyan and Dmitry Namiot
The proliferation of agentic AI coding assistants, including Claude Code, GitHub Copilot, Cursor, and emerging skill-based architectures, has fundamentally transformed software development workflows. These systems leverage Large
Language Models (LLMs) integrated with external tools, file systems, and shell access through protocols like the Model Context Protocol (MCP). However, this expanded capability surface introduces critical security vulnerabilities. In this Systematization of Knowledge (SoK) paper, we present a comprehensive analysis of
prompt injection attacks targeting agentic coding assistants. We propose a novel three-dimensional taxonomy categorizing attacks across delivery vectors, attack modalities, and propagation behaviors. Our meta-analysis synthesizes findings from 78 recent studies (2021–2026), consolidating evidence that attack success rates against state-of-the-art defenses exceed 85% when adaptive attack strategies are employed. We systematically catalog 42 distinct attack techniques spanning input manipulation, tool poisoning, protocol exploitation,
multimodal injection, and cross-origin context poisoning. Through critical analysis of 18 defense mechanisms reported in prior work, we identify that most achieve less than 50% mitigation against sophisticated adaptive attacks. We contribute: (1) a unified taxonomy bridging disparate attack classifications, (2) the first systematic analysis of skill-based architecture vulnerabilities with concrete exploit chains, and (3) a defense-in-depth framework grounded in the limitations we identify. Our findings indicate that the security community must treat
prompt injection as a first-class vulnerability class requiring architectural-level mitigations rather than ad-hoc filtering approaches.
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Cryptography and Security
CTF for education
Yi Lyu, Luke Dotson, Nic Draves et al. (+1 more)
In this paper, we take a close look at how CTF can be used in cybersecurity education. We divide the CTF competitions into four different categories, which are attack-based CTFs, defense-based CTFs, jeopardy CTFs and gamified and wargames CTFs. We start our analysis by summarizing the main characteristics of different CTF types. We then compare them with each other in both learning objectives and other aspects like accessibility. We conclude that combining all four CTF formats can help participants build one's cybersecurity knowledge. By doing that, we hope that our findings will provide some useful insights for future CTF educators.
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All authors Yi Lyu, Luke Dotson, Nic Draves, Andy Zhang
Cryptography and Security
Reconstructing Training Data from Adapter-based Federated Large Language Models
Silong Chen, Yuchuan Luo, Guilin Deng et al. (+4 more)
Adapter-based
Federated Large
Language Models (FedLLMs) are widely adopted to reduce the computational, storage, and communication overhead of full-parameter fine-tuning for web-scale applications while preserving user
privacy. By freezing the backbone and training only compact low-rank adapters, these methods appear to limit gradient leakage and thwart existing Gradient Inversion Attacks (GIAs). Contrary to this assumption, we show that low-rank adapters create new, exploitable leakage channels. We propose the Unordered-word-bag-based Text Reconstruction (UTR) attack, a novel GIA tailored to the unique structure of adapter-based FedLLMs. UTR overcomes three core challenges: low-dimensional gradients, frozen backbones, and combinatorially large reconstruction spaces by: (i) inferring
token presence from
attention patterns in frozen layers, (ii) performing sentence-level inversion within the low-rank subspace of adapter gradients, and (iii) enforcing semantic coherence through constrained greedy decoding guided by
language priors. Extensive experiments across diverse models (GPT2-Large, BERT, Qwen2.5-7B) and
datasets (CoLA, SST-2, Rotten Tomatoes) demonstrate that UTR achieves near-perfect reconstruction accuracy (ROUGE-1/2 > 99), even with large batch size settings where prior GIAs fail completely. Our results reveal a fundamental tension between parameter efficiency and
privacy in FedLLMs, challenging the prevailing belief that lightweight adaptation inherently enhances security. Our code and data are available at https://github.com/shwksnshwowk-wq/GIA.
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All authors Silong Chen, Yuchuan Luo, Guilin Deng, Yi Liu, Min Xu, Shaojing Fu, Xiaohua Jia
Cryptography and Security · Cross-listed from quant-ph
Are Quantum Voting Protocols Practical?
Nitin Jha and Abhishek Parakh
Quantum voting protocols aim to offer ballot secrecy and publicly verifiable tallies using physical guarantees from
quantum mechanics, rather than relying solely on computational hardness. This article surveys whether such
quantum voting protocols are practical. We begin by outlining core mathematical ideas such as the superposition principle, the no-cloning
theorem, and
quantum entanglement. We then define a common system and threat model, identifying key actors, trust assumptions, and security goals. Representative protocol families are reviewed, including
entanglement-based schemes with central tallying, self-tallying designs that enable public verification, and authority-minimized approaches that certify untrusted devices through observable correlations. Finally, we evaluate implementation challenges, including loss, noise, device imperfections, scalability, and coercion resistance, and discuss realistic near-term deployment scenarios for small-scale elections.
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Cryptography and Security
On the Feasibility of Simulation-Secure Quantum Functional Encryption
Mohammed Barhoush, Arthur Mehta, Anne Müller et al. (+1 more)
Functional encryption is a powerful cryptographic primitive that enables fine-grained access to encrypted data and underlies numerous applications. Although the ideal security notion for FE, simulation security, has been shown to be impossible in the plain classical setting, those impossibility results rely on inherently classical arguments. This raises a fundamental question: can simulation-secure FE be realized in the
quantum regime or in alternative models? We resolve both directions of this question. On the negative side, we show that the classical impossibility results largely extend to the
quantum setting. When the adversary can submit an unbounded number of challenge messages, we establish an unconditional impossibility, matching the classical barrier. In the case where the adversary may obtain many functional keys, classical arguments only yield impossibility under the assumption of pseudorandom functions; we strengthen this by proving impossibility under the potentially weaker assumption of pseudorandom
quantum states. We additionally give an independent impossibility based solely on public-key encryption with classical public-keys. Since public-key encryption is not known to imply pseudorandom states, this yields complementary evidence of the barrier and, in particular, establishes unconditional impossibility of public-key functional encryption with classical public-keys. A key technical ingredient in our proofs is a novel incompressibility property for pseudorandom states, which may be of independent interest. On the positive side, we show how to circumvent these fundamental barriers in
memory-restricted models, where the adversary's
quantum or classical
memory is bounded. In this setting, we obtain new feasibility results for simulation-secure FE that allow many challenge ciphertexts or many functional key queries.
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All authors Mohammed Barhoush, Arthur Mehta, Anne Müller, Louis Salvail
Cryptography and Security
PatchIsland: Orchestration of LLM Agents for Continuous Vulnerability Repair
Wonyoung Kim, Seunggi Min, Minjae Gwon et al. (+11 more)
Continuous fuzzing platforms such as OSS-Fuzz uncover large numbers of vulnerabilities, yet the subsequent repair process remains largely manual. Unfortunately, existing Automated Vulnerability Repair (AVR) techniques – including recent LLM-based systems – are not directly applicable to continuous fuzzing. This is because these systems are designed and evaluated on a static, single-run
benchmark setting, making them ill-suited for the diverse, noisy, and failure-prone environments in continuous fuzzing. To address these issues, we introduce PatchIsland, a system for Continuous Vulnerability Repair (CVR) that tightly integrates with continuous fuzzing pipelines. PatchIsland employs an ensemble of diverse LLM
agents. By leveraging multiple LLM
agents, PatchIsland can cover a wider range of settings (e.g., different projects, bug types, and programming
languages) and also improve operational robustness. In addition, PatchIsland utilizes a two-phase patch-based deduplication to mitigate duplicate crashes and patches, which can be problematic in continuous fuzzing. In our internal evaluation, PatchIsland repaired 84 of 92 vulnerabilities, demonstrating strong repair capability. In the official AIxCC competition, the system operated with no human intervention in a fully autonomous environment and successfully patched 31 out of 43 vulnerabilities, achieving a repair rate of 72.1%.
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All authors Wonyoung Kim, Seunggi Min, Minjae Gwon, Dowoo Baik, Haein Lee, Hyeon Heo, Minjae Lee, Min Woo Baek, Yonghwi Jin, Younggi Park, Yunjae Choi, Taesoo Kim, Sangdon Park, Insu Yun
Cryptography and Security · Cross-listed from cs.SE
YASA: Scalable Multi-Language Taint Analysis on the Unified AST at Ant Group
Yayi Wang, Shenao Wang, Jian Zhao et al. (+7 more)
Modern enterprises increasingly adopt diverse technology stacks with various programming
languages, posing significant challenges for static application security testing (SAST). Existing taint analysis tools are predominantly designed for single
languages, requiring substantial engineering effort that scales with
language diversity. While multi-
language tools like CodeQL, Joern, and WALA attempt to address these challenges, they face limitations in intermediate representation design, analysis precision, and extensibility, which make them difficult to scale effectively for large-scale industrial applications at Ant Group. To bridge this gap, we present YASA (Yet Another Static Analyzer), a unified multi-
language static taint analysis framework designed for industrial-scale deployment. Specifically, YASA introduces the Unified Abstract Syntax Tree (UAST) that provides a unified abstraction for compatibility across diverse programming
languages. Building on the UAST, YASA performs point-to analysis and taint propagation, leveraging a unified semantic model to manage
language-agnostic constructs, while incorporating
language-specific semantic models to handle other unique
language features. When compared to 6 single- and 2 multi-
language static analyzers on an industry-standard
benchmark, YASA consistently outperformed all baselines across Java, JavaScript, Python, and Go. In real-world deployment within Ant Group, YASA analyzed over 100 million lines of code across 7.3K internal applications. It identified 314 previously unknown taint paths, with 92 of them confirmed as 0-day vulnerabilities. All vulnerabilities were responsibly reported, with 76 already patched by internal development teams, demonstrating YASA's practical effectiveness for securing large-scale industrial software systems.
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All authors Yayi Wang, Shenao Wang, Jian Zhao, Shaosen Shi, Ting Li, Yan Cheng, Lizhong Bian, Kan Yu, Yanjie Zhao, Haoyu Wang
Cryptography and Security
Prompt and Circumstances: Evaluating the Efficacy of Human Prompt Inference in AI-Generated Art
Khoi Trinh, Scott Seidenberger, Joseph Spracklen et al. (+4 more)
The emerging field of AI-generated art has witnessed the rise of
prompt marketplaces, where creators can purchase, sell, or share
prompts to generate unique artworks. These marketplaces often assert ownership over
prompts, claiming them as intellectual property. This paper investigates whether concealed
prompts sold on
prompt marketplaces can be considered bona fide intellectual property, given that humans and AI tools may be able to infer the
prompts based on publicly advertised sample images accompanying each
prompt on sale. Specifically, our study aims to assess (i) how accurately humans can infer the original
prompt solely by examining an AI-generated image, with the goal of generating images similar to the original image, and (ii) the possibility of improving upon individual human and AI
prompt inferences by crafting combined human and AI
prompts with the help of a large
language model. Although previous research has explored AI-driven
prompt inference and protection strategies, our work is the first to incorporate a human subject study and examine collaborative human-AI
prompt inference in depth. Our findings indicate that while
prompts inferred by humans and
prompts inferred through a combined human and AI effort can generate images with a moderate level of similarity, they are not as successful as using the original
prompt. Moreover, combining human- and AI-inferred
prompts using our suggested merging techniques did not improve performance over purely human-inferred
prompts.
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All authors Khoi Trinh, Scott Seidenberger, Joseph Spracklen, Raveen Wijewickrama, Bimal Viswanath, Murtuza Jadliwala, Anindya Maiti
Cryptography and Security
Res-MIA: A Training-Free Resolution-Based Membership Inference Attack on Federated Learning Models
Mohammad Zare and Pirooz Shamsinejadbabaki
Membership inference attacks (MIAs) pose a serious threat to the
privacy of machine learning models by allowing adversaries to determine whether a specific data sample was included in the training set. Although
federated learning (FL) is widely regarded as a
privacy-aware training paradigm due to its decentralized nature, recent evidence shows that the final global model can still leak sensitive membership information through black-box access. In this paper, we introduce Res-MIA, a novel training-free and black-box membership inference attack that exploits the sensitivity of deep models to high-frequency input details. Res-MIA progressively degrades the input resolution using controlled downsampling and restoration operations, and analyzes the resulting confidence decay in the model's predictions. Our key insight is that training samples exhibit a significantly steeper confidence decline under resolution erosion compared to non-member samples, revealing a robust membership signal. Res-MIA requires no shadow models, no auxiliary data, and only a limited number of forward queries to the target model. We evaluate the proposed attack on a
federated ResNet-18 trained on CIFAR-10, where it consistently outperforms existing training-free baselines and achieves an AUC of up to 0.88 with minimal computational overhead. These findings highlight frequency-sensitive overfitting as an important and previously underexplored source of
privacy leakage in
federated learning, and emphasize the need for
privacy-aware model designs that reduce reliance on fine-grained, non-robust input features.
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Cryptography and Security · Cross-listed from cs.LG
Robust Privacy: Inference-Stage Privacy through Certified Robustness
Jiankai Jin, Xiangzheng Zhang, Zhao Liu et al. (+4 more)
An adversary observing a model's released prediction can infer sensitive attributes of the queried input, or even reconstruct representatives of the model's training data. The inference interface thus acts as a side channel for
privacy leakage. We introduce Robust
Privacy (RP), an inference-stage
privacy notion inspired by certified robustness: if a model's prediction is provably invariant within a radius-$R$ neighborhood around an input $x$ with confidence at least $1-\alpha$, then $x$ enjoys $(R,\alpha)$-Robust
Privacy, under which we prove that any adversary observing the released prediction has at most $\alpha/2$ advantage in distinguishing $x$ from any input within distance $R$ of $x$. Building on RP, we formalize Robust Attribute
Privacy (RAP), an attribute-level
privacy notion that characterizes the set of sensitive-attribute values that remain compatible with a released prediction. On a classification task, RP increases the median length of the RAP-compatible inference interval from $23.50$ to $29.96$, reducing attribute-inference precision. Model inversion attacks, often treated as a training-stage threat, in fact rely on fine-grained input-output dependence signals leaked through the inference interface; RP masks these signals at the inference stage, reducing attack success rate (ASR) from $73\%$ to $4\%$ on a black-box inversion attack. This direct targeting of the leakage channel enables RP to dominate DP-SGD and randomized response in the
privacy-utility tradeoff space: RP retains $98.4\%$ accuracy at $21\%$ ASR, whereas DP-SGD must drop accuracy to $61.7\%$ to reach a comparable ASR. Across both experiments, increasing the smoothing sample size $N$ at fixed noise scale strengthens
privacy and improves utility together. Finally, we examine model
distillation as a scope boundary and show that RP mitigates attribute-level and instance-level inference-stage
privacy leakage.
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All authors Jiankai Jin, Xiangzheng Zhang, Zhao Liu, Wenzhuo Xu, Dongdong Yang, Deyue Zhang, Quanchen Zou
Cryptography and Security
Obfuscation as an Effective Signal for Prioritizing Cross-Chain Smart Contract Audits: Large-Scale Measurement and Risk Profiling
Yao Zhao, Zhang Sheng, Shengchen Duan et al. (+3 more)
Obfuscation raises the interpretation cost of smart-contract
auditing, yet its signals are hard to transfer across chains. We present HOBFNET, a fast surrogate of OBFPROBE, enabling million-scale cross-chain scoring. The model aligns with tool outputs on Ethereum (PCC 0.9158, MAPE 8.20 percent) and achieves 8-9 ms per contract, yielding a 2.3k-5.2k times speedup. Across BSC, Polygon, and Avalanche, we observe systematic score drift, motivating within-chain percentile queues (p99 as the main queue, p99.9 as an emergency queue). The high-score tail is characterized by rare selectors, external-call enrichment, and low signature density, supporting secondary triage. Cross-chain reuse is tail-enriched and directionally biased from smaller to larger ecosystems. On two publicly alignable cross-chain spillover cases, both fall into the p99 queue, indicating real-world hit value. We deliver a two-tier audit queue and a cross-chain linkage workflow for practical security operations.
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All authors Yao Zhao, Zhang Sheng, Shengchen Duan, Shen Wang, Daoyuan Wu, Zhiyuan Wan