While retrieval-augmented generation systems partially address the hallucination issues in large language models, it also introduces new vulnerabilities to knowledge corruption attacks. Adversaries exploit these vulnerabilities by poisoning documents provided by RAG system to manipulate LLM outputs. To counter this threat, we propose SecureCollaRAG, a Byzantine-tolerant collaborative RAG framework leveraging Multi-source Knowledge Validation Mechanism. Our approach enables agent system to securely verify document provenance through dynamic GNN-based credibility scoring, effectively preventing stealthy knowledge corruption attacks while preserving essential domain knowledge integrity. Through extensive evaluations and formal analysis, we demonstrate that SecureCollaRAG maintains robustness against attackers under non-IID data distributions.

Smart contracts are highly susceptible to manipulation attacks due to the leakage of sensitive information. Addressing manipulation vulnerabilities is particularly challenging because they stem from inherent data confidentiality issues rather than straightforward implementation bugs. To tackle this by preventing sensitive information leakage, we present PARTITIONGPT, the first LLM-driven approach that combines static analysis with the in-context learning capabilities of large language models (LLMs) to partition smart contracts into critical (privileged) and normal codebases, guided by a few annotated sensitive data variables. We evaluated PARTITIONGPT on 18 annotated smart contracts containing 99 sensitive functions. The results demonstrate that PARTITIONGPT successfully generatescompilable, andverifiedpartitions, achieving a precision of 80% while reducing more than 26% code compared to functionlevel partitioning approach. Furthermore, we evaluated PARTITIONGPT on nine real-world manipulation attacks that led to a total loss of 25 million dollars, PARTITIONGPT effectively prevents eight cases, highlighting its potential for broad applicability and the necessity for secure program partitioning during smart contract development to diminish manipulation vulnerabilities.

DeFi (Decentralized Finance) is one of the most important applications of today’s cryptocurrencies and smart contracts. It manages hundreds of billions in Total Value Locked (TVL) on-chain, yet it remains susceptible to common DeFi price manipulation attacks. Despite state-of-the-art (SOTA) systems like DeFiRanger and DeFort, we found that they are less effective to non-standard price models in custom DeFi protocols, which account for 44.2% of the 95 DeFi price manipulation attacks reported over the past three years.In this paper, we introduce the first LLM-based approach, DeFiScope, for detecting DeFi price manipulation attacks in both standard and custom price models. Our insight is that large language models (LLMs) have certain intelligence to abstract price calculation from smart contract source code and infer the trend of token price changes based on the extracted price models. To further strengthen LLMs in this aspect, we leverage Foundry to synthesize on-chain data and use it to fine-tune a DeFi price-specific LLM. Together with the high-level DeFi operations recovered from low-level transaction data, DeFiScope detects various DeFi price manipulations according to systematically mined patterns. Experimental results show that DeFiScope achieves a high recall of 80% on real-world attacks, a precision of 96% on suspicious transactions, and zero false alarms on benign transactions, significantly outperforming SOTA approaches. Moreover, we evaluate DeFiScope’s cost-effectiveness and demonstrate its practicality by helping our industry partner confirm 147 real-world price manipulation attacks, including discovering 81 previously unknown historical incidents.

Smart contracts are computer programs running on blockchains to implement Decentralized Applications. The absence of contract specifications hinders routine tasks, such as contract understanding and testing. In this work, we propose a specification mining approach to infer contract specifications from past transaction histories. Our approach derives high-level behavioral automata of function invocations, accompanied by program invariants statistically inferred from the transaction histories. We implemented our approach as tool SMCON and evaluated it on eleven well-studied Azure benchmark smart contracts and six popular real-world DApp smart contracts. The experiments show that SMCON mines reasonably accurate specifications that can be used to enhance symbolic analysis of smart contracts achieving higher code coverage and up to 56 % speedup, and facilitate DApp developers in maintaining high-quality documentation and test suites.

Smart contracts are computer programs running on blockchains to automate the transaction execution between users. The absence of contract specifications poses a real challenge to the correctness verification of smart contracts. Program invariants are properties that are always preserved throughout the execution, which characterize an important aspect of the program behaviors. In this paper, we propose a novel invariant generation framework, INVCON+, for Solidity smart contracts. INVCON+ extends the existing invariant detector, InvCon, to automatically produce verified contract invariants based on both dynamic inference and static verification. Unlike INVCON+, InvCon only produces likely invariants, which have a high probability to hold, yet are still not verified against the contract code. Particularly, INVCON+ is able to infer more expressive invariants that capture richer semantic relations of contract code. We evaluate INVCON+ on 361 ERC20 and 10 ERC721 real-world contracts, as well as common ERC20 vulnerability benchmarks. The experimental results indicate that INVCON+ efficiently produces high-quality invariant specifications, achieving a recall of 80%, which can be used to secure smart contracts from 17 types of common vulnerabilities.

Subsequently, by executing various attacks on benchmark datasets such as MNIST, we construct Federated Learning Malicious Parameter Identification (FLMPID) dataset to enable malicious client detection. Building on this dataset, we propose FORTRESS (Federated POisoning-Resistance Defense via Dual-Domain Distance and TRust AssESSment), a framework designed to detect and mitigate malicious updates from clients. FORTRESS employs a unique encoder-decoder architecture. The encoder utilizes dual-domain distance metrics on weights and gradients to extract hidden representations, while the decoder leverages Actor-Critic (AC) reinforcement learning for trust assessment. We evaluated FORTRESS under multiple attack scenarios and demonstrated its defense effectiveness, making it a promising solution for enhancing the security of FL systems.

Decentralized Finance (DeFi) is a prominent application of smart contracts, representing a novel financial paradigm in contrast to centralized finance. While DeFi applications are rapidly emerging on mainstream blockchain platforms, their quality varies greatly, presenting numerous challenges, particularly in terms of their governance mechanisms. In this paper, we present a comprehensive study of governance issues in DeFi applications. Initially, we collected 3,165 academic papers and numerous industry reports. After thorough screening, we selected 44 academic papers and 11 industry reports for detailed analysis. Drawing upon insights from industry reports and academic research articles, we develop a taxonomy to categorize these governance issues. We collect and build a dataset of 4,446 audit reports from seventeen Web3 security companies, categorizing their governance issues according to our constructed taxonomy. We conducted a thorough analysis of governance issues and identified vulnerabilities in the governance design and implementation, e.g., voting sybil attack and proposal front-running. Our statistical analysis indicates that a significant portion (35.48%) of governance-related issues is classified as severe. Within these, ownership-related problems constitute the largest share (65.38%). Despite DeFi governance being essential for the long-term success of DeFi projects, our data shows that both auditors and development teams have not fully grasped its significance. Based on audit reports, we also analyzed common vulnerabilities and issues in the governance domain. Our research identifies two primary categories of DeFi governance issues: technology-centric and human-centric. Technology-centric issues can be addressed through technology updates and iterations, whereas human-centric issues are influenced not only by the development team's technical skills but also by their understanding of DeFi governance. Data analysis reveals that design and implementation issues are frequently overlooked; although not directly associated with vulnerabilities, these issues can impact the equitable distribution of project benefits. Furthermore, our analysis of 104 projects’ tokenomics configurations, including 15 collected from DeFi platforms, uncovered 27 inconsistent configurations, with only two projects exhibiting no issues. This suggests that such issues are relatively common. We therefore advise project teams to ensure consistency between their tokenomics design and the actual code. Our study culminates in providing several key practical implications for various DeFi stakeholders, including developers, users, researchers, and regulators, aiming to deepen the understanding of DeFi governance issues and contribute to the robust growth of DeFi systems.

Blockchain’s inherent immutability, while transformative, creates critical security risks in smart contracts, where undetected vulnerabilities can result in irreversible financial losses. Current auditing tools and approaches often address specific vulnerability types, yet there is a need for a comprehensive solution that can detect a wide range of vulnerabilities with high accuracy. We propose LLM-SmartAudit, a novel framework that leverages Large Language Models (LLMs) to automate smart contract vulnerability detection and analysis. Using a multi-agent conversational architecture with a buffer-of-thought mechanism, LLM-SmartAudit maintains a dynamic record of insights generated throughout the audit process. This enables a collaborative system of specialized agents to iteratively refine their assessments, enhancing the accuracy and depth of vulnerability detection. To evaluate its effectiveness, LLM-SmartAudit was tested on three datasets: a benchmark for common vulnerabilities, a real-world project corpus, and a CVE dataset. It outperformed existing tools with 98% accuracy on common vulnerabilities and demonstrates higher accuracy in real-world scenarios. Additionally, it successfully identifies 12 out of 13 CVEs, surpassing other LLM-based methods. These results demonstrate the effectiveness of multi-agent collaboration in automated smart contract auditing, offering a scalable, adaptive, and highly efficient solution for blockchain security analysis.

Smart contracts are susceptible to various security issues, among which access control (AC) vulnerabilities are particularly critical. While existing research has proposed multiple detection tools, automatic and appropriate repair of AC vulnerabilities in smart contracts remains a challenge. Unlike commonly supported vulnerability types by existing repair tools, such as reentrancy, which are usually fixed by template-based approaches, the main obstacle of repairing AC vulnerabilities lies in identifying the appropriate roles or permissions amid a long list of non-AC-related source code to generate proper patch code, a task that demands human-level intelligence.In this paper, we employ the state-of-the-art GPT-4 model and enhance it with a novel approach called ACFIX. The key insight is that we can mine common AC practices for major categories of code functionality and use them to guide LLMs in fixing code with similar functionality. To this end, ACFIX involves offline and online phases. In the offline phase, ACFIX mines a taxonomy of common Role-based Access Control practices from 344,251 on-chain contracts, categorizing 49 role-permission pairs from the top 1,000 unique samples. In the online phase, ACFIX tracks AC-related elements across the contract and uses this context information along with a Chain-of-Thought pipeline to guide LLMs in identifying the most appropriate role-permission pair for the subject contract and subsequently generating a suitable patch. To evaluate ACFIX, we built the first benchmark dataset of 118 real-world AC vulnerabilities, and our evaluation revealed that ACFIX successfully repaired 94.92% of them, a major improvement compared to the baseline GPT-4 at only 52.54%. We also conducted a human study to understand the value of ACFIX’s repairs and their differences from human repairs.

Although Decentralized Finance (DeFi) applications facilitate tamper-proof transactions among multiple anonymous users, since attackers can access the smart contract bytecode directly, vulnerabilities in the transaction mechanism, contract code, or third-party components can be easily exploited to manipulate token prices, leading to financial losses. Since price manipulation often relies on specific states and complex trading sequences, existing detection tools have limitations in addressing this problem. In addition, to swiftly identify the root cause of an attack and implement targeted defense and remediation measures, auditors typically prioritize understanding the methodology behind the attack, emphasizing 'how' it occurred rather than simply confirming its existence. To address these problems, this paper presents a novel automatic price manipulation detection and analysis framework, named DeFort, which contains a price manipulation behavior model to guide on-chain detection, multiple price monitoring strategies to detect pools with abnormal token prices, and various profit calculation mechanisms to confirm attacks. Based on behavioral models, DeFort can automatically locate transactions and functions that cause abnormal price fluctuations and identify attackers and victims. Experimental results demonstrate that DeFort can outperform state-of-the-art price manipulation detection methods. Furthermore, after monitoring 441 real-world projects for two months, DeFort successfully detected five price manipulation attacks.

Smart contracts, self-executing programs on the blockchain, facilitate reliable value exchanges without centralized oversight. Despite the recent focus on dynamic analysis of their transaction histories in both industry and academia, no open-source tool currently offers comprehensive tracking of complete transaction information to extract user-desired data such as invariant-related data. This paper introduces OpenTracer, designed to address this gap. OpenTracer guarantees comprehensive tracking of every execution step, providing complete transaction information. OpenTracer has been employed to analyze 350,800 Ethereum transactions, successfully inferring 23 different types of invariant from predefined templates. The tool is fully open-sourced, serving as a valuable resource for developers and researchers aiming to extract or validate new invariants from transaction traces. A demonstration video of OpenTracer is available at https://youtu.be/vTdmjWdYd30. The source code of OpenTracer is available at https://github.com/jeffchen006/OpenTracer.

Smart contracts deployed on permissionless blockchains, such as Ethereum, are accessible to any user in a trustless environment. Therefore, most smart contract applications implement access control policies to protect their valuable assets from unauthorized accesses. A difficulty in validating the conformance to such policies, i.e., whether the contract implementation adheres to the expected behaviors, is the lack of policy specifications. In this paper, we mine past transactions of a contract to recover a likely access control model, which can then be checked against various information flow policies and identify potential bugs related to user permissions. We implement our role mining and security policy validation in tool SPCon. The experimental evaluation on labeled smart contract role mining benchmark demonstrates that SPCon effectively mines more accurate user roles compared to the state-of-the-art role mining tools. Moreover, the experimental evaluation on real-world smart contract benchmark and access control CVEs indicates SPCon effectively detects potential permission bugs while having better scalability and lower false-positive rate compared to the state-of-the-art security tools, finding 11 previously unknown bugs and detecting six CVEs that no other tool can find.

Smart contracts are gaining popularity as a means to support transparent, traceable, and self-executing decentralized applications, which enable the exchange of value in a trustless environment. Developers of smart contracts rely on various libraries, such as OpenZeppelin for Solidity contracts, to improve application quality and reduce development costs. The API documentations of these libraries are important sources of information for developers who are unfamiliar with the APIs. Yet, maintaining high-quality documentations is non-trivial, and errors in documentations may place barriers for developers to learn the correct usages of APIs. In this paper, we propose a technique, DocCon, to detect inconsistencies between documentations and the corresponding code for Solidity smart contract libraries. Our fact-based approach allows inconsistencies of different severity levels to be queried, from a database containing precomputed facts about the API code and documentations. DocCon successfully detected high-priority API documentation errors in popular smart contract libraries, including mismatching parameters, missing requirements, outdated descriptions, etc. Our experiment result shows that DocCon achieves good precision and is applicable to different libraries: 29 and 22 out of our reported 40 errors have been confirmed and fixed by library developers so far.

Smart contracts are self-governed computer programs that run on blockchain to facilitate asset transfer between users within a trustless environment. The absence of contract specifications hinders routine tasks, such as program understanding, debugging, testing, and verification of smart contracts. In this work, we propose a unified specification mining framework to infer specification models from past transaction histories. These include access control models describing high-level authorization rules, program invariants capturing low-level program semantics, and behavior models characterizing interaction patterns allowed by contract implementations. The extracted specification models can be used to perform conformance checking on smart contracts, with the goal of eliminating unforeseen contract quality issues.

Smart contracts are self-executing computer programs deployed on blockchain to enable trustworthy exchange of value without the need of a central authority. With the absence of documentation and specifications, routine tasks such as program understanding, maintenance, verification, and validation, remain challenging for smart contracts. In this paper, we propose a dynamic invariant detection tool, InvCon, for Ethereum smart contracts to mitigate this issue. The detected invariants can be used to not only support the reverse engineering of contract specifications, but also enable standard-compliance checking for contract implementations. InvCon provides a Web-based interface and a demonstration video of it is available at: https://youtu.be/Y1QBHjDSMYk.

Most of the existing smart contract symbolic execution tools perform analysis on bytecode, which loses high-level semantic information presented in source code. This makes interactive analysis tasks—such as visualization and debugging—extremely challenging, and significantly limits the tool usability. In this paper, we present SolSEE, a source-level symbolic execution engine for Solidity smart contracts. We describe the design of SolSEE, highlight its key features, and demonstrate its usages through a Web-based user interface. SolSEE demonstrates advantages over other existing source-level analysis tools in the advanced Solidity language features it supports and analysis flexibility. A demonstration video is available at: https://sites.google.com/view/solsee/.

Despite the high stakes involved in smart contracts, they are often developed in an undisciplined manner, leaving the security and reliability of blockchain transactions at risk. In this article, we introduce ContraMaster—an oracle-supported dynamic exploit generation framework for smart contracts. Existing approaches mutate only single transactions; ContraMaster exceeds these by mutating the transaction sequences. ContraMaster uses data-flow, control-flow, and the dynamic contract state to guide its mutations. It then monitors the executions of target contract programs, and validates the results against a general-purpose semantic test oracle to discover vulnerabilities. Being a dynamic technique, it guarantees that each discovered vulnerability is a violation of the test oracle and is able to generate the attack script to exploit this vulnerability. In contrast to rule-based approaches, ContraMaster has not shown any false positives, and it easily generalizes to unknown types of vulnerabilities (e.g., logic errors). We evaluate ContraMaster on 218 vulnerable smart contracts. The experimental results confirm its practical applicability and advantages over the state-of-the-art techniques, and also reveal three new types of attacks.

Smart contracts are computer programs allowing users to define and execute transactions automatically on top of the blockchain platform. Many of such smart contracts can be viewed as games. A game-like contract accepts inputs from multiple participants, and upon ending, automatically derives an outcome while distributing assets according to some predefined rules. Without clear understanding of the game rules, participants may suffer from fraudulent advertisements and financial losses. In this paper, we present a framework to perform (semi-)automated verification of smart contract fairness, whose results can be used to refute false claims with concrete examples or certify contract implementations with respect to desired fairness properties. We implement FairCon, which is able to check fairness properties including truthfulness, efficiency, optimality, and collusion-freeness for Ethereum smart contracts. We evaluate FairCon on a set of real-world benchmarks and the experiment result indicates that FairCon is effective in detecting property violations and able to prove fairness for common types of contracts.

Unlike those on public permissionless blockchains, smart contracts on enterprise permissioned blockchains are not limited by resource constraints, and therefore often larger and more complex. Current testing and analysis tools lack support for such contracts, which demonstrate stateful behaviors and require special treatment in quality assurance. In this paper, we present a model-based testing platform, called ModCon, relying on user-specified models to define test oracles, guide test generation, and measure test adequacy. ModCon is Web-based and supports both permissionless and permissioned blockchain platforms. We demonstrate the usage and key features of ModCon on real enterprise smart contract applications.