# EIP-155: Replay Protection

[EIP-155](https://eips.ethereum.org/EIPS/eip-155) is an Ethereum Improvement Proposal that introduces replay protection for transactions by including the chain ID in the signed transaction data. This prevents replay attacks, where a valid transaction from one network is rebroadcasted on another network without the sender’s consent.

This was necessary, because Ethereum-based transactions rely on the Hex representation of addresses, which are not necessarily unique to a given network. This means that single signed transaction could be valid on multiple networks, as the same addresses are involved e.g. in a token transfer. This holds the potential for exploits and is addressed by enforcing the EIP-155 replay protection.

Cosmos SDK-based blockchains use Bech32 representations for addresses, which contain a unique prefix per chain. This means, that for Cosmos transactions, replay protection is inherently present as addresses of a given chain are not valid addresses on other chains. However, as LagomChain also accepts EVM transactions, handling only those transactions that conform to EIP-155 becomes a requirement again.

This requires special care to be taken when selecting an EIP-155 compliant [chain ID](/concepts/chain-id.md) to avoid duplication amongst chains.

### Configuring Replay Protection[​](broken://pages/fubw0AiV3zvxDzf0ACoT) <a href="#configuring-replay-protection" id="configuring-replay-protection"></a>

By default, replay protection is enabled on any LagomChain node. There are two distinct steps required to accept unprotected transactions, i.e. those that do not contain the chain ID in the signed transaction data:

1. **Disable Module Parameter**: The [EVM module](/modules/evm.md) contains a governance controlled parameter, that globally dictates if unprotected transactions are supported. This has to be disabled via a governance vote or by setting the `allow_unprotected_txs` field to `true` in the genesis of a [local node](/lagomchain-cli/single-node.md).
2. **Adjust Node Configuration**: When the global parameter is set accordingly, each node operator has the option to individually opt into allowing unprotected transactions to be sent to their nodes. This configuration is explained in the section on node configuration.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.lagomchain.com/concepts/eip-155-replay-protection.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.