nunoedgarhubsoftphotoflow / 0xproject.contracts

0x smart contracts and tests.

0x Smart Contracts

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0x is an open protocol that facilitates trustless and low-friction exchange of Ethereum-based assets. This repository contains the system of Ethereum smart contracts comprising 0x protocol's shared settlement layer, native token (ZRX) and decentralized governance structure. Truffle is used for deployment. Mocha and Chai are used for unit tests.

Architecture

Contracts

Exchange.sol

Exchange contains all business logic associated with executing trades and cancelling orders. Exchange accepts order data packets that conform to 0x protocol message format, allowing for off-chain order relay with on-chain settlement. Exchange is designed to be replaced as protocol improvements are adopted over time. It follows that Exchange does not have direct access to ERC20 token allowances; instead, all transfers are carried out by Proxy on behalf of Exchange.

Proxy.sol

Proxy is analagous to a valve that may be opened or shut by MultiSigWallet, either allowing or preventing Exchange from executing trades. Proxy plays a key role in 0x protocol's update mechanism: old versions of the Exchange contract may be deprecated, preventing them from executing further trades. New and improved versions of the Exchange contract are given permission to execute trades through decentralized governance implemented within a DAO (for now we use MultiSigWallet as a placeholder for DAO).

MultiSigWallet.sol

MultiSigWallet is a temporary placeholder contract that will be replaced by a thoroughly researched, tested and audited DAO. MultiSigWallet is the only entity with permission to grant or revoke access to the Proxy and, by extension, ERC20 token allowances. MultiSigWallet is assigned as the owner of Proxy and, once a suitable DAO is developed, MultiSigWallet will call Proxy.transferOwnership(DAO) to transfer permissions to the DAO.

TokenRegistry.sol

TokenRegistry stores metadata associated with ERC20 tokens. TokenRegistry entries may only be created/modified/removed by MultiSigWallet (until it is replaced by a suitable DAO), meaning that information contained in the registry will generally be trustworthy. 0x message format is not human-readable making it difficult to visually verify order parameters (token addresses and exchange rates); the TokenRegistry can be used to quickly verify order parameters against audited metadata.

Protocol Specification

Off-chain Relay, On-chain Settlement

Message Format

Each order is a data packet containing order parameters and an associated signature. Order parameters are concatenated and hashed to 32 bytes via the Keccak SHA3 function. The order originator signs the order hash with their private key to produce an ECDSA signature.

Name	Data Type	Description
version	address	Address of the Exchange contract. This address will change each time the protocol is updated.
maker	address	Address originating the order.
taker	address	Address permitted to fill the order (optional).
tokenM	address	Address of an ERC20 Token contract.
tokenT	address	Address of an ERC20 Token contract.
valueM	uint256	Total units of tokenM offered by maker.
valueT	uint256	Total units of tokenT requested by maker.
expiration	uint256	Time at which the order expires (seconds since unix epoch).
feeRecipient	address	Address that recieves transaction fees (optional).
feeM	uint256	Total units of ZRX paid to feeRecipient by maker.
feeT	uint256	Total units of ZRX paid to feeRecipient by taker.
v	uint8	ECDSA signature of the above arguments.
r	bytes32	ECDSA signature of the above arguments.
s	bytes32	ECDSA signature of the above arguments.

Setup

Install Node v6.9.1

Install truffle

npm i -g truffle@^3.2.1

Install ethereumjs-testrpc

npm i -g ethereumjs-testrpc@^3.0.2

Install project dependencies:

npm install

Running tests

Start Testrpc

testrpc --networkId 42

Compile contracts

truffle compile

Run tests

npm run test

Contributing

Style guide

We adhere to the Airbnb javascript style guide.

In order to see style violation errors, install an eslinter for your text editor. e.g Atom's linter-eslint.