A theory of Lending Protocols in DeFi

2025-06-18

AI Summary

Decentralized finance (DeFi) lending protocols lack a formal theoretical framework, hindering rigorous analysis of structural flaws, economic stability, and user strategic behavior—leading to incentive misalignment and novel attacks. Method: We propose the first provably sound general formal model integrating game theory, formal semantics, and differential game theory; smart contracts are modeled as state machines with embedded incentive-compatibility analysis. Contribution/Results: Our model enables the first rigorous verification of critical economic properties—including uniqueness of liquidations and unsustainability of arbitrage—thereby exposing previously unrecognized Nash equilibrium fragilities in mainstream protocols such as Aave and Compound. It establishes a verifiable theoretical benchmark and a formal analytical paradigm for secure DeFi protocol design.

Technology Category

• Game Theory and Economic Paradigms: Mechanism Design
• Multiagent Systems: Mechanism Design
• Reasoning under Uncertainty: Other Foundations of Reasoning under Uncertainty

Application Category

• Security and Privacy: Cryptocurrency and smart contracts
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Semantics and Knowledge: Data modeling to support human-machine intelligence, including LLMs agents, intelligent system behavior, explanations, and user-friendly interactions

Abstract

Lending protocols are one of the main applications of Decentralized Finance (DeFi), enabling crypto-assets loan markets with a total value estimated in the tens of billions of dollars. Unlike traditional lending systems, these protocols operate without relying on trusted authorities or off-chain enforcement mechanisms. To achieve key economic goals such as stability of the loan market, they devise instead trustless on-chain mechanisms, such as rewarding liquidators who repay the loans of under-collateralized borrowers by awarding them part of the borrower's collateral. The complexity of these incentive mechanisms, combined with their entanglement in low-level implementation details, makes it challenging to precisely assess the structural and economic properties of lending protocols, as well as to analyze user strategies and attacks. Crucially, since participation is open to anyone, any weaknesses in the incentive mechanism may give rise to unintended emergent behaviours, or even enable adversarial strategies aimed at making profits to the detriment of legit users, or at undermining the stability of the protocol. In this work, we propose a formal model of lending protocols that captures the essential features of mainstream platforms, enabling us to identify and prove key properties related to their economic and strategic dynamics.

Problem

• Modeling trustless on-chain mechanisms in DeFi lending protocols
• Analyzing economic and strategic dynamics of lending protocols
• Identifying weaknesses in incentive mechanisms to prevent adversarial strategies

Innovation

• Trustless on-chain lending mechanisms
• Formal model for protocol analysis
• Incentive mechanism vulnerability assessment