EVM Opcode: COINBASE

The COINBASE opcode (0x41) pushes the current block's coinbase address onto the stack. In Solidity, this is exposed as block.coinbase.

The term comes from Bitcoin, where the first transaction in every block is called the coinbase transaction. This is the transaction that mints new coins as the block reward, and the address receiving that reward is the coinbase address. Ethereum kept the same concept: each block has a coinbase field that identifies who gets paid for producing it.

On Ethereum, the feeRecipient is an address set by the block builder to collect priority fees. On Cronos, there is no miner or fee recipient. Cronos uses Cosmos SDK BFT consensus where blocks are proposed by validators, so COINBASE returns the EVM address of the validator that proposed the current block.

Behaviour Comparison

• Ethereum: COINBASE returns the feeRecipient set by the block builder, usually a wallet or contract that receives priority fees.

• Cronos: COINBASE returns the EVM address of the current block's proposing validator. This address is not set up to receive contract calls or transfers.

What This Means for Your Contract

• Sending CRO to block.coinbase does not work as a miner bribe. On Ethereum, searchers often pay miners directly using block.coinbase.transfer(amount). On Cronos, this sends CRO to the validator's derived EVM address, which the validator does not monitor or control for this purpose.

• Using block.coinbase as an access control check is unreliable. The block proposer rotates each block based on Cosmos SDK validator selection, so you cannot predict or rely on a specific address being the proposer.

• Reading block.coinbase for logging works fine. If you only read the value for informational purposes (e.g. recording which validator proposed a block), it is valid and stable within a given block.

Audit any Ethereum contract that uses block.coinbase before deploying on Cronos. Contracts that send CRO to block.coinbase or use it as a fee-recipient address will not behave as expected.

Checking the Value

Via Smart Contract (Solidity)

If you are writing a smart contract, you can read it directly by accessing the variable in your functions:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract MinerReader {
    function getMinerAddress() public view returns (address) {
        // Reads the coinbase address of the current block
        return block.coinbase; 
    }
}

Via Cronos Explorer

The coinbase address for any block is shown on Cronos Explorer under the Validator field on the block detail page. For example: https://explorer.cronos.com/block/81008315

Via JSON-RPC

curl https://evm.cronos.com/ \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest",false],"id":1}'

The miner field in the response is the coinbase address:

{
   "id": 1,
   "result": {
       ...
       "hash": "0x...",
       "miner": "0x1e0c93bb9abcc94f24916a6d571450ae62462ecd",
       "mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
       "nonce": "0x0000000000000000",
       "number": "0x4d416bb",
       ...
   },
   "jsonrpc": "2.0"
}