CoinFlipper

Utility

0x5bd4a6d9fa20...669957527b12

FrontierContract #83Source VerifiedEdit this contract

Deployed August 8, 2015 (11 years ago)Block 55,563

A coin flip settled on the parity of the block timestamp, with a size guard written the wrong way round so no bet can ever be placed.

Frontier EraVerified Source

Historical Significance

An early gambling contract that shows both hazards of the form at once: a payout decided by a value the block producer controls, and a guard written backwards that made the whole contract inert. The author noticed the second problem within the hour and redeployed; the timestamp problem went on being repeated by dice contracts for years.

Context

Ethereum's Frontier network went live on 30 July 2015. Almost nothing was deployed in its first months except tutorial code and small experiments, written in a Solidity only a few months old and with no test network in common use, so the experiments happened on mainnet.

Key Facts

Deployer

0xc70ba2...af62e9

Deployment Block

55,563

Deployment Date

Aug 8, 2015, 10:25 PM

Code Size

186.0 B

Gas at Deploy

66,999

Deployment Transaction: 0x621e22c902569720...55a9658208d62c3a

Description

A gambling contract with two entry points. donate() takes ether and does nothing with it. The fallback function is the bet: it compares the stake against the contract's own balance, records the block timestamp in a public variable, and pays the sender twice the stake when that timestamp is odd.

The guard is inverted. It requires the stake to be smaller than twice the balance and returns otherwise, but the balance it reads already includes the stake just received, so the condition holds for every non-zero bet and the function returns before reaching the flip. No bet placed on this contract can ever be settled.

The same account deployed a corrected version sixty four blocks later, with the comparison the other way around.

Settling on block.timestamp would have been unsafe in any case: the miner producing the block chooses it within a tolerance, and here the payout is twice the stake.

Heuristic Analysis

The following characteristics were detected through bytecode analysis and may not be accurate.

Detected Type: Utility

Frontier Era

The initial release of Ethereum. A bare-bones implementation for technical users.

Block span: 0 — 1,149,999

July 30, 2015 — March 14, 2016

Bytecode Overview

Opcodes186

Unique Opcodes56

Jump Instructions13

Storage Operations2

Verified Source Available

This contract has verified source code on Etherscan.

Verified on Etherscan

Show source code (Solidity)

// Submitted by EthereumHistory (ethereumhistory.com)
contract CoinFlipper {
    uint256 public flip;
    function donate() {
    }
    function() {
        var v = msg.value;
        var b = address(this).balance;
        if (v < 2 * b) {
            return;
        }
        flip = block.timestamp;
        if (flip % 2 == 0) {
        } else {
            msg.sender.send(2 * v);
        }
    }
}