Hardfork Meta: Byzantium

EIP-609 is a proposal for the hard fork named Byzantium, also known as Metropolis/Byzantium or Metropolis part 1. The activation of this hard fork is set to occur at block >= 4,370,000 on the Mainnet and block >= 1,700,000 on the Ropsten testnet. The proposal includes several Ethereum Improvement Proposals (EIPs) such as EIP-100, which changes the difficulty adjustment to target mean block time including uncles, and EIP-140, which introduces the REVERT instruction in the Ethereum Virtual Machine. Other EIPs included in the proposal are EIP-196, EIP-197, and EIP-198, which introduce precompiled contracts for addition and scalar multiplication on the elliptic curve alt_bn128, optimal ate pairing check on the elliptic curve alt_bn128, and bigint modular exponentiation, respectively. Additionally, EIP-211 introduces new opcodes RETURNDATASIZE and RETURNDATACOPY, while EIP-214 introduces a new opcode STATICCALL. EIP-649 delays the difficulty bomb and reduces block rewards, while EIP-658 embeds transaction status code in receipts. Overall, the proposal aims to improve the efficiency and security of the Ethereum network.