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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 by 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.
The chain ID returned should always correspond to the information in the current known head block. This ensures that caller of this RPC method can always use the retrieved information to sign transactions built on top of the head.
If the current known head block does not specify a chain ID, the client should treat any calls to eth_chainId as though the method were not supported, and return a suitable error.
Parameters
None.
Returns
QUANTITY - integer of the current chain ID.
Example
js
curl -X POST --data '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":83}'
// 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 fetches 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.
Security Considerations
Consumers should prefer eth_chainId over net_version, so that they can reliably identify chain they are communicating with.
Implementers should take care to implement eth_chainId correctly and promote its use, since the chain ID is critical in replay attack prevention as described in EIP-155, and consumers will rely on it to identify the chain they are communicating with.
Implementation
Reference
Return value QUANTITY adheres to standard JSON RPC hex value encoding, as documented in the Ethereum.org documentation.
Copyright
Copyright and related rights waived via CC0.