Cross-Chain Replay Risk Explainer

WHAT IT DOES

Cross-Chain Replay Risk Explainer is a read-only tool that analyzes transactions for cross-chain replay attack vulnerabilities and generates AI-powered plain-language explanations of replay risk. It reads transaction signature, chain ID, nonce, transaction calldata, contract bytecode, chain-specific EIP-155 protection status, replay protection parameters, transaction hash, sender address, target contract address, cross-chain deployment patterns, and known replay vulnerability history. The tool then presents this data alongside an AI-generated explanation of whether the transaction is vulnerable to replay attacks, what conditions would allow replay, and recommended protective measures — helping you avoid having a transaction maliciously replayed on another chain.

HOW TO USE

Connect your wallet using the BGWallet bridge and select your target network. Enter the transaction hash you want to analyze. Optionally enter a target contract address. Click "Analyze replay risk" to read on-chain data. The tool displays the transaction hash, chain ID, nonce, EIP-155 protection status, and replay risk level (Safe or Vulnerable). A prominent warning banner appears if a vulnerability is detected. Detailed information includes sender, target contract, calldata hash, bytecode hash, replay protection parameters, deployment pattern, known replay vulnerability history, and cross-chain deployment status. A recommendation box provides specific protective measures. An AI explanation appears below the on-chain data, describing whether the transaction is vulnerable to cross-chain replay attacks, what conditions would allow replay, and recommended protective measures before you sign and broadcast the transaction. The wallet's own signature step still protects you — this explanation is informational only and does not replace reviewing what you approve in your wallet.

TECHNICAL MECHANISM

The tool uses ethers.js v5.7.2 with the provider from the BGWallet bridge to read on-chain transaction data. No hardcoded contract addresses are used — you are always in control of which contract you trust. When analyzing replay risk, the tool reads the transaction signature by parsing the signed transaction data (via getTransaction()), reads the chain ID from the transaction's signature (extracted via v, r, s values), reads the nonce from the transaction, reads the transaction calldata from the transaction object, reads the contract bytecode via provider.getCode(targetContract) for comparison, reads chain-specific EIP-155 protection status by checking whether the chain ID was included in the signature (v value), reads replay protection parameters from the chain's configuration (e.g., chain ID in signature), reads the transaction hash from the user input, reads sender address from the transaction, reads target contract address from the transaction or user input, identifies cross-chain deployment patterns by comparing the contract's bytecode and metadata against known patterns for each chain, and checks known replay vulnerability history against a database of past replay incidents. The tool fetches event logs by walking backwards in chunks and halving chunk size on failure, ensuring logs are properly read despite varying RPC limitations. The data is formatted and passed to the AI bridge via BGAI.generate() with a structured prompt that includes all the on-chain data read. The AI is instructed to analyze whether the transaction is vulnerable to cross-chain replay attacks, explain what conditions would allow replay, and recommend protective measures — while stating plainly that it cannot guarantee that a transaction is replay-safe across all chains, and cannot detect replay vulnerabilities in contracts that use non-standard replay protection. The AI response is capped at 1,024 tokens to ensure concise, focused replay risk assessments. All computed values are guarded against negative numbers — if a chain ID or nonce appears invalid, the tool flags it rather than displaying nonsensical values.

WHAT IT CANNOT SEE

This tool cannot guarantee that a transaction is replay-safe across all chains. It cannot detect replay vulnerabilities in contracts that use non-standard replay protection. It cannot detect malicious intent behind cross-chain transaction replay attempts beyond signature and chain ID analysis. The AI explanation is generated from on-chain data only and cannot detect non-standard replay protection mechanisms, proxy pattern complexities, or off-chain replay attempts. It cannot predict whether a malicious actor will attempt to replay a transaction on another chain. The tool does not continuously monitor replay risks; each analysis is a snapshot at the time of the lookup. It cannot detect delayed replay attempts, nonce reuse on other chains, or stale signature data. The tool does not store any data persistently; all state is in-memory and resets on reload. The AI explanation is informational and does not constitute financial advice, legal advice, or a guarantee of transaction safety or replay protection.

PLEASE NOTE

Cross-Chain Replay Risk Explainer works exclusively with EVM-compatible chains. It requires a Web3 wallet (MetaMask or similar) and the BGWallet bridge. Explanations are AI-generated from data the app reads on-chain — always review what you are actually signing in your wallet before approving it. Cross-chain replay attacks carry significant risk including unauthorized execution of transactions on other chains, loss of funds, and unexpected contract behavior. Use this tool as a guide only; always cross-check with chain-specific documentation and independent security resources for critical decisions. This is experimental software; use at your own risk.