A Collusion-Resistant DECO-Based Attestation Protocol for Practical Applications

Accessing off-chain web data is crucial for expanding blockchain functionality and enabling a broader range of decentralized applications. Oracle protocols with designated verifiers such as DECO, enable this access while preserving data integrity, but they are open to collusion attacks for direct smart contract interactions, particularly when a single verifier is responsible for proof validation. A recent proposal introduced verifier multiplexing, transitioning from a single verifier to a t-out-of-n model using Distributed Verifiable Random Functions (DVRFs) to minimize the risk of collusion. However, this approach relies on trusted storage, limiting its practicality. In this paper, we enhance this approach by integrating Threshold Signature Schemes (TSS), enabling consensus among t-out-of-n verifiers to establish a practical protocol preserving the security against the collusion attack. Furthermore, we demonstrate the seamless integration of DVRF and TSS through a single Distributed Key Generation (DKG) process, improving network efficiency. This proposed protocol not only strengthens the security of blockchain oracles but also serves as an independent, modular solution that can be integrated into various integrity-preserving mechanisms to mitigate collusion threats effectively. Finally, we present a usecase example demonstrating how the proposed protocol can be applied to develop a real-world application.