0x6f0b...df0d

Lottery / Gambling

0x6f0b707c8513...6ca7218fdf0d

FrontierContract #783Exact Bytecode MatchEdit this contract

Deployed September 3, 2015 (11 years ago)Block 180,417

A coin flip wager contract that draws its outcome from the previous block hash, endowed with 1 ETH on 3 September 2015.

Frontier EraVerified Source

Historical Significance

Randomness is the problem gambling contracts exist to expose. Every value available inside the EVM is either known in advance or chosen by the account producing the block, so a payout decided from block data can be steered by whoever mines it. This run of revisions is that lesson being learned in public, one deployment at a time, and the answer the ecosystem eventually reached, an oracle or a commit and reveal, is not available here at all.

Context

Deployed a month after the Frontier launch, when no contract could yet draw randomness from anything but block data.

Key Facts

Deployer

Cyrus Adkisson(0xcf684d...ad1bac)

Deployment Block

180,417

Deployment Date

Sep 3, 2015, 06:26 PM

Code Size

2.5 KB

Gas at Deploy

712,277

Transactions by Year

20152

Deployment Transaction: 0x0be1f8759aac713b...9c3afb97a7001da4

Description

The last of a run of revisions deployed across two days, and the one where the block hash finally works. It reads block.blockhash(block.number - 1) rather than the current block, whose hash does not exist while it is being executed, and folds that into the hash that decides the flip alongside block difficulty, the coinbase address, the timestamp and the wager. The source comments reason about why the bettor cannot know the deciding hash at the time of the bet. A kill function was used, so no code remains and the source is matched against the bytecode as archived at deployment. Deployed by Cyrus Adkisson from 0xcf684dfb8304729355b58315e8019b1aa2ad1bac.

Source Verified

Exact bytecode match(2,590 bytes)

Compiler: v0.1.1+

View verification proof

Historian Categories

Lottery / Gambling

Heuristic Analysis

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

Detected Type: Lottery / Gambling

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

Opcodes2,590

Unique Opcodes150

Jump Instructions128

Storage Operations49

Verified Source Available

Source verified through compiler archaeology and exact bytecode matching.

View Verification Proof

Show source code (Solidity)

// Submitted by EthereumHistory (ethereumhistory.com)
// This contract is designed to demonstrate the generation of a random number.
// If you submit a betAndFlip() request after block 180,000 has just been mined,
// (i.e. block 180,000 is the "best block" on stats.ethdev.gov and the most recent listed on any block explorer site), 
// then the transaction will get mined/processed in block 180,001. (most of the time, anyway... it may be a block or two later)
// Once the transaction is mined, then block.number will become 180,002 while the flipping is underway.
// Any attempt to get block.blockhash(180,002) will return 0x000000000...
// That's why betAndFlip uses blocknumber - 1 for its hash.
// At first I thought "Wait, if we have to use the block in past, couldn't the gambler know that?" And the answer is "no". 
// All the gambler knows at the time of bet submission is 180,000. We use 180,001 which is brand new and known and 180,002 is underway.

// NOTE: Use more gas on the betAndFlip(). I set mine to 1,000,000 and the rest is automatically refunded (I think). At current prices 9/3/2015, that's negligible anyway.

contract CoinFlipper {

    address creator;
    uint contract_creation_value;	// original endowment
    int lastgainloss;
    string lastresult;
    uint lastblocknumberused;
    bytes32 lastblockhashused;

    function CoinFlipper() private 
    {
        creator = msg.sender; 								
        lastresult = "no wagers yet";
        lastgainloss = 0;
    }
	
    function getEndowmentBalance() constant returns (uint)
    {
    	return this.balance;
    }
    
    // this is probably unnecessary and gas-wasteful. The lastblockhashused should be random enough. Adding the rest of these deterministic factors doesn't change anything. 
    // This does, however, let the bettor introduce a random seed by wagering different amounts. wagering 1 ETH will produce a completely different hash than 1.000000001 ETH
    function sha(uint128 wager) constant private returns(uint256)  	// DISCLAIMER: This is pretty random... but not truly random.
    { 
        return uint256(sha3(block.difficulty, block.coinbase, now, lastblockhashused, wager));  
    }
    
    function betAndFlip() public               
    {
    	if(msg.value > 340282366920938463463374607431768211455)  	// value can't be larger than (2^128 - 1) which is the uint128 limit
    	{
    		lastresult = "wager too large";
    		lastgainloss = 0;
    		msg.sender.send(msg.value); // return wager
    		return;
    	}		  
    	else if((msg.value * 2) > this.balance) 					// contract has to have 2*wager funds to be able to pay out. (current balance INCLUDES the wager sent)
    	{
    		lastresult = "wager larger than contract's ability to pay";
    		lastgainloss = 0;
    		msg.sender.send(msg.value); // return wager
    		return;
    	}
    	else if (msg.value == 0)
    	{
    		lastresult = "wager was zero";
    		lastgainloss = 0;
    		// nothing wagered, nothing returned
    		return;
    	}
    		
    	uint128 wager = uint128(msg.value);          				// limiting to uint128 guarantees that conversion to int256 will stay positive
    	
    	lastblocknumberused = block.number - 1 ;
    	lastblockhashused = block.blockhash(lastblocknumberused);
    	
	   	uint hash = sha(wager);
	    if( hash % 2 == 0 )
	   	{
	    	lastgainloss = int(wager) * -1;
	    	lastresult = "loss";
	    	// they lost. Return nothing.
	    	return;
	    }
	    else
	    {
	    	lastgainloss = wager;
	    	lastresult = "win";
	    	msg.sender.send(wager * 2);  // They won. Return bet and winnings.
	    } 		
    }
    
  	function getLastBlockNumberUsed() constant returns (uint)
    {
        return lastblocknumberused;
    }
    
    function getLastBlockHashUsed() constant returns (bytes32)
    {
    	return lastblockhashused;
    }

    function getResultOfLastFlip() constant returns (string)
    {
    	return lastresult;
    }
    
    function getPlayerGainLossOnLastFlip() constant returns (int)
    {
    	return lastgainloss;
    }
        
    /**********
     Standard kill() function to recover funds 
     **********/
    
    function kill()
    { 
        if (msg.sender == creator)
        {
            suicide(creator);  // kills this contract and sends remaining funds back to creator
        }
    }
}

/*

var coinflipperContract = web3.eth.contract([{
    "constant": true,
    "inputs": [],
    "name": "getPlayerGainLossOnLastFlip",
    "outputs": [{
        "name": "",
        "type": "int256"
    }],
    "type": "function"
}, {
    "constant": false,
    "inputs": [],
    "name": "betAndFlip",
    "outputs": [],
    "type": "function"
}, {
    "constant": true,
    "inputs": [],
    "name": "getLastBlockNumberUsed",
    "outputs": [{
        "name": "",
        "type": "uint256"
    }],
    "type": "function"
}, {
    "constant": false,
    "inputs": [],
    "name": "kill",
    "outputs": [],
    "type": "function"
}, {
    "constant": true,
    "inputs": [],
    "name": "getEndowmentBalance",
    "outputs": [{
        "name": "",
        "type": "uint256"
    }],
    "type": "function"
}, {
    "constant": true,
    "inputs": [],
    "name": "getLastBlockHashUsed",
    "outputs": [{
        "name": "",
        "type": "bytes32"
    }],
    "type": "function"
}, {
    "constant": true,
    "inputs": [],
    "name": "getResultOfLastFlip",
    "outputs": [{
        "name": "",
        "type": "string"
    }],
    "type": "function"
}, {
    "inputs": [],
    "type": "constructor"
}]);

var coinflipper = coinflipperContract.new({
    from: web3.eth.accounts[0],
    data: '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',
    gas: 1000000,
    value: 1000000000000000000 // endowment of 1 eth
}, function(e, contract) {
    if (typeof contract.address != 'undefined') {
        console.log(e, contract);
        console.log('Contract mined! address: ' + contract.address + ' transactionHash: ' + contract.transactionHash);
    }
});

// ********** after deployment

> coinflipper.getEndowmentBalance();
6000000000000000000
> coinflipper.betAndFlip.sendTransaction({from:eth.coinbase, value: 1000000000000000000}); // 1 ETH. Let's see what happens
"0xc78a24881c7f70d25a817dcfcdce3347ca0cd265b7ba30a60df61e5639482bcf"
> coinflipper.getResultOfLastFlip();
"no wagers yet"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet?
"no wagers yet"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet?
"no wagers yet"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"no wagers yet"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"win"
> coinflipper.getPlayerGainLossOnLastFlip();
1000000000000000000
> web3.fromWei(coinflipper.getPlayerGainLossOnLastFlip());
1
> coinflipper.getEndowmentBalance();
5000000000000000000
> coinflipper.betAndFlip.sendTransaction({from:eth.coinbase, value: 3000000000000000000}); // 3 ETH. Let's see what happens
"0xcae272652649e07c343674d15b40a086c559408d9c66d8022de3f54932bf3d9f"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"loss"
> coinflipper.getEndowmentBalance();
8000000000000000000
> web3.fromWei(coinflipper.getPlayerGainLossOnLastFlip());
-3
> web3.eth.getBalance(eth.coinbase);
1806931309200681965
> web3.fromWei(web3.eth.getBalance(eth.coinbase));
1.806931309200681965
> coinflipper.betAndFlip.sendTransaction({from:eth.coinbase, value: 1500000000000000000}); // 1.5 ETH. Let's see what happens
"0xc99add577b3180ca58b1a8219f2cd282f6b77edb63e1e384b05abc434753b1a1"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"win"
> web3.fromWei(web3.eth.getBalance(eth.coinbase));
3.304471659200681965
> web3.fromWei(web3.eth.getBalance(eth.coinbase));
> coinflipper.kill.sendTransaction({from:eth.coinbase});
"0xed9f9e49cca76965ba32acce2b2f0b17ada467e52d55b803c26cc7132ba108fa"
  
  
 // ************** after separate deployment with smaller endowment to test payout safety limit
 
  Contract mined! address: 0xb0824b45f4a4c1ee4df356378d555c7f4366fa4c transactionHash: 0x065580a137654a816abdeb27e690e6c96f59dce92a9e8064f6f8c3c49cf0b681

> coinflipper.getEndowmentBalance();   // 1 eth
1000000000000000000
> coinflipper.betAndFlip.sendTransaction({from:eth.coinbase, value: 3000000000000000000}); // 3 ETH, more than endowment can handle. Let's see what happens
"0x66b5ae12f215d1bcf1a1656f79ccedc69612dc891f35dce5dbd6ead8854f0cb1"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"no wagers yet"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"no wagers yet"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"no wagers yet"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"wager larger than contract's ability to pay"
> coinflipper.getEndowmentBalance();
1000000000000000000
> coinflipper.betAndFlip.sendTransaction({from:eth.coinbase, value: 500000000000000000}); // .5 ETH.
"0x16ef5f3f0778b1252dcfd3b55f09ab97382f23d8ad7489f1f1b45d88eb7588f5"
> coinflipper.getResultOfLastFlip(); // has the tx been mined yet? I'm waiting...
"loss"
  
  
  
 */

External Links

Etherscan Verified Source (if any)

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