EIP 695: Create `eth_chainId` method for JSON-RPC

Author	Isaac Ardis, Wei Tang, Fan Torchz
Discussions-To	https://ethereum-magicians.org/t/eip-695-create-eth-chainid-method-for-json-rpc/1845
Status	Last Call (review ends 2019-07-20)
Type	Standards Track
Category	Interface
Created	2017-08-21
Requires	155, 1474

Simple Summary

Include eth_chainId method in eth_-namespaced JSON-RPC methods.

Abstract

The eth_chainId method should return a single STRING result for an integer value in hexadecimal format, describing the currently configured CHAIN_ID value used for signing replay-protected transactions, introduced via EIP-155.

Motivation

Currently although we can use net_version RPC call to get the current network ID, there’s no RPC for querying the chain ID. This makes it impossible to determine the current actual blockchain using the RPC.

Specification

`eth_chainId`

Returns the currently configured chain ID, a value used in replay-protected transaction signing as introduced by EIP-155.

Parameters

None.

Returns

QUANTITY - integer of the current chain ID.

Example

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":1}'

// Result
{
  "id": 83,
  "jsonrpc": "2.0",
  "result": "0x3d" // 61
}

Rationale

An ETH/ETC client can accidentally connect to an ETC/ETH RPC endpoint without knowing it unless it tries to sign a transaction or it fetch a transaction that is known to have signed with a chain ID. This has since caused trouble for application developers, such as MetaMask, to add multi-chain support.

Backwards Compatibility

Not relevant.

Implementation

Reference

Return value QUANTITY adheres to standard JSON RPC hex value encoding, as documented here: https://github.com/ethereum/wiki/wiki/JSON-RPC#hex-value-encoding.

EIP 695: Create `eth_chainId` method for JSON-RPC Source