Block Context Instructions

// Time-locked functionality
contract TimeLock {
    uint256 public unlockTime;

    function withdraw() public {
        require(block.timestamp >= unlockTime, "Still locked");
        // Withdrawal logic
    }
}

// DEPRECATED: Not secure for production
function randomNumber() public view returns (uint256) {
    return uint256(keccak256(abi.encodePacked(
        blockhash(block.number - 1),
        block.timestamp,
        block.difficulty  // Now PREVRANDAO post-merge
    )));
}

// Cross-chain contract behavior
function getToken() internal view returns (address) {
    if (block.chainid == 1) return MAINNET_TOKEN;
    if (block.chainid == 137) return POLYGON_TOKEN;
    revert("Unsupported chain");
}

// Verify past block hash
function verifyProof(uint256 blockNumber, bytes32 expectedHash) public view returns (bool) {
    require(block.number - blockNumber <= 256, "Block too old");
    return blockhash(blockNumber) == expectedHash;
}

// VULNERABLE: Exact timestamp matching
require(block.timestamp == expectedTime);

// SAFER: Range checking
require(block.timestamp >= startTime && block.timestamp <= endTime);

function getBlockHash(uint256 blockNum) public view returns (bytes32) {
    require(blockNum < block.number, "Future block");
    require(block.number - blockNum <= 256, "Block too old");
    return blockhash(blockNum);
}

// EIP-155: Replay-protected transaction signing
bytes32 hash = keccak256(abi.encodePacked(
    nonce, gasPrice, gasLimit, to, value, data, chainId, 0, 0
));

import { BlockHandlers } from '@tevm/voltaire/evm/block';
import { createFrame } from '@tevm/voltaire/evm/Frame';

// Create frame with block context
const frame = createFrame({
  blockContext: {
    block_number: 18_000_000n,
    block_timestamp: 1696000000n,
    block_coinbase: coinbaseAddress,
    block_gas_limit: 30_000_000n,
    block_base_fee: 20_000_000_000n,
    chain_id: 1n,
  }
});

// Execute block opcode
const handlers = BlockHandlers(frame);
const err = handlers.timestamp(frame);