store proofs using publicly accessible storage

[janfilips]

See this -

contracts/notary.sol

// TODO: replace this with storage, this needs to be accessible from newly deployed contracts
// right now, when you deploy a new contract, all this information is being lost as it is stored in an in-memory per-contract base.
mapping (bytes32 => bool) private proofs;

The problem is that the content of the "proofs" dissapears once a new contract (with a new address) is deployed. Wee need to store this differently so that it is publicly accessible using multiple contracts.

[janfilips]

for an inspiration see this -

https://github.com/jparicka/blockchain-voting/blob/development/contracts/example-voting-contract-0.so

[janfilips]

/**

• @title IPFS hash handler
• @dev IPFS multihash handler. Does a small check to validate that a multihash is
• correct by validating the digest size byte of the hash. For example, the IPFS
• Multihash "QmPtkU87jX1SnyhjAgUwnirmabAmeASQ4wGfwxviJSA4wf" is the base58
• encoded form of the following data:

• ┌────┬────┬───────────────────────────────────────────────────────────────────┐
  

• │byte│byte│             variable length hash based on digest size             │
  

• ├────┼────┼───────────────────────────────────────────────────────────────────┤
  

• │0x12│0x20│0x1714c8d0fa5dbe9e6c04059ddac50c3860fb0370d67af53f2bd51a4def656526 │
  

• └────┴────┴───────────────────────────────────────────────────────────────────┘
  

•   ▲    ▲                                   ▲
  

•   │    └───────────┐                       │
  

• hash function digest size hash value
• we still store the data as bytes since it is inherently a variable length structure.
• @dev See multihash format: https://git.io/vbooc
  */

contract DependentOnIPFS {
/**

• @dev Validate a multihash bytes value
  */
  function isValidIPFSMultihash(bytes _multihashBytes) internal pure returns (bool) {
  require(_multihashBytes.length > 2);
  uint8 _size;
  // There isn't another way to extract only this byte into a uint8
  // solhint-disable no-inline-assembly
  assembly {
  // Seek forward 33 bytes beyond the solidity length value and the hash function byte
  _size := byte(0, mload(add(_multihashBytes, 33)))
  }
  return (_multihashBytes.length == _size + 2);
  }
  }

[janfilips]

done