bcmember

This registry system for the Blockchain Catalunya association (https://www.blockchaincatalunya.org)

Disclaimer

This is a "hobby-mode" project. It cointain bugs, non-documented code, etc...

BTW I'm learning golang, so if you find something that could be improved, structure, etc... please let's me know!

Folder contents

• contracts/ the assets smartcontract, this smartcontract will hold all the assets generated by the association to his associates. The main contract is the Assets.sol

• web/ is the associate mobile-friendy web application.

• server/ is the backend system for the web. golang <3

• aragonapp/ is a wrapper for using the assets contract inside with the amazing aragonOs (see https://aragon.one )

The assets contract

It's a custom non-fungible token

NOTE: This is not a decentralized token, this means that tokens can be created and destroyed by the smartcontract owners and administrators. The Blockchain Catalunya association v1.0 is a centralized organization.

the API:

• mint(address _owner, uint16 _class, bool _transferable, uint64 _caducity, string _description)

  • _owner of the asset
  • _class of asset (id card, a specific training, etc...)
  • _transferable if the owner can transfer the asset to other member or not
  • _caducity of the asset
  • _description (short) of the asset

• burn(uint128 _serial)

  • _serial to be burnt

• transfer(uint128 _serial, address _to, bool _notify)

  • _serial of asset being transferred
  • _to the recipient
  • _notify execute callback onAssetsFallback on the recipient address

• transferOffchain(uint128 _serial, address _to, uint64 _nonce, uint8 _v, bytes32 _r, bytes32 _s)

  • the same of transfer but with an offline generated signature see tests for an example. You need to use an incremental nonce here.

• setCustomAttr1(uint128 _serial, bytes32 _value)

  • the owner of the asset can set an field in their assets with some value
  • _serial of the asset
  • _value to be set

• setCustomAttr2(uint128 _serial, bytes32 _value)

  • the owner of the contract can set an field in their assets with some value. this is usefull, for instance, to set a SWARM/IPFS hash of a better representation of the asset.
  • _serial of the asset
  • _value to be set

The web application

A friend helped me to write a decent and modern-looking web application, but ok, I am not a web developer, I am a security guy, so expect rare things here.

• ui.js is the class managing all the user interface stuff, it's the controller
• bc.js manages the communication with the backend server and the blockchain

Maybe here it's where makes sense to explain how authorization works:

briefly:

• User generates a keypair in the browser and keeps it the browser storage
• Webapp sends a JSONRPC bc_register message to the server (yes, the server talks JSONRPC not JSON/REST) with the associate but also sending an Authorization HTTP header with the signature of the JSONRPC message made with the user private key. See the _postSignedJsonRpc function here. Server processes it.
• Server will respond with a JWT token, this JWT token will be used by the client as an authorization for the web3, since backend also acts as a web3 gateway.

+-----+               +---------+     +-------+
| web |               | server  |     | geth  |
+-----+               +---------+     +-------+
   |                       |              |
   | generate keypair      |              |
   |-----------------      |              |
   |                |      |              |
   |<----------------      |              |
   |                       |              |
   | signed JSONRPC        |              |
   |---------------------->|              |
   |                       |              |
   |                   JWT |              |
   |<----------------------|              |
   |                       |              |
   | web3call + JWT        |              |
   |---------------------->|              |
   |                       |              |
   |                       | web3call     |
   |                       |------------->|
   |                       |              |
   |                       |     response |
   |                       |<-------------|
   |                       |              |
   |              response |              |
   |<----------------------|              |
   |                       |              |

The server

The server is writen in golang <3 and have the following endpoints:

• /web3 the web3 JWT-authorized gateway
• /dapp is serving the webapp
• /rpc is serving the signed JSONRPC calls
• /config retrieves the server parameters needed by the webapp

There's a configuration file template in template-bcserver.yaml

How to start the system

• deploy the contracts/contract/Assets.sol smartcontract
• create a configuration file named yournostname-bcserver.yaml, with the configuration parameters (see the template)
• go to web/ and run npm i && npm run dist
• go to server/ and run make get, and make run (you need golang installed)