InsuranceLedger.sol

pragma solidity ^0.4.21;

contract InsuranceLedger {
  // Event to broadcast to the network when a new motorbike has been added
  event OnRecordMotorbike(bytes32 _hashedChassisNumber);

  // The address of the contract owner (Seraphin), set when the contract is deployed
  address public seraphinAddress = msg.sender;
  // The mapping with all insured motorbikes - we stick to an extremely simple
  // model representation with only the hashed chassis number. A given hashed
  // chassis number is either insured or not, that is, true or false in this
  // mapping.
  // Note that calling Insurances[nonExistingEntry] returns false, which is what
  // we need in our case (only recorded motorbikes are considered to be insured).
  // Using Structs, we could easily extend this mapping to add datapoints such
  // as licence plate, insurance policy subscriber, dates of insurance coverage etc.
  // Note that bytes32 = 1 byte * 32 = 8 bits * 32 = 256 bits, which is the
  // length of the SHA3-256 hash we use to encrypt the motorbike chassis number.
  mapping (bytes32 => bool) public Insurances;

  // Function modifier, added to a function to ensure only Seraphin can call this
  // function (in a broader ecosystem, we'd have something like 'onlyByInsurers')
  modifier onlyBySeraphin {
    require(msg.sender == seraphinAddress);
    _;
  }

  // WRITE function to record a new motorbike on the Blockchain, callable only
  // by Seraphin for now. If calling the function from Remix, don't forget to
  // preceed the SHA3-256 hash with an 0x flag to let the contract know that
  // the hash is already in the correct hexadecimal format.
  function recordMotorbike(bytes32 _hashedChassisNumber) public onlyBySeraphin {
    Insurances[_hashedChassisNumber] = true;
    emit OnRecordMotorbike(_hashedChassisNumber);
  }

  // READ function to check if a given motorbike is insured - callable by anyone.
  // Similarly to the write function, one needs to call this function with an
  // 0x flag preceding the input parameter to reflect its hexadecimal format.
  function insured(bytes32 _hashedChassisNumber) public constant returns (bool){
    return Insurances[_hashedChassisNumber];
  }
}