ACon$^2$: Adaptive Conformal Consensus for Provable Blockchain Oracles

TL;DR

This paper introduces ACon$^2$, an adaptive consensus algorithm for blockchain oracles that ensures data correctness under adversarial conditions using online uncertainty quantification, demonstrated on price datasets and Ethereum.

Contribution

The paper proposes a novel adaptive conformal consensus algorithm that improves blockchain oracle reliability by handling distribution shifts and Byzantine failures.

Findings

Effective consensus set derived from multiple oracles

Guarantees correctness under adversarial conditions

Practical implementation demonstrated on Ethereum

Abstract

Blockchains with smart contracts are distributed ledger systems that achieve block-state consistency among distributed nodes by only allowing deterministic operations of smart contracts. However, the power of smart contracts is enabled by interacting with stochastic off-chain data, which in turn opens the possibility to undermine the block-state consistency. To address this issue, an oracle smart contract is used to provide a single consistent source of external data; but, simultaneously, this introduces a single point of failure, which is called the oracle problem. To address the oracle problem, we propose an adaptive conformal consensus (ACon$^2$) algorithm that derives a consensus set of data from multiple oracle contracts via the recent advance in online uncertainty quantification learning. Interesting, the consensus set provides a desired correctness guarantee under distribution shift and Byzantine adversaries. We demonstrate the efficacy of the proposed algorithm on two price datasets and an Ethereum case study. In particular, the Solidity implementation of the proposed algorithm shows the potential practicality of the proposed algorithm, implying that online machine learning algorithms are applicable to address security issues in blockchains.