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0x is an open protocol that facilitates trustless, low friction exchange of Ethereum-based assets. A full description of the protocol may be found in our whitepaper. This repository contains the system of Ethereum smart contracts comprising 0x protocol's shared on-chain settlement layer, native token (ZRX) and decentralized governance structure. Truffle is used for deployment. Mocha is used for unit tests.

Table of Contents

• Architecture
• Contracts
  • Descriptions
  • Deployed Addresses
    • Kovan
• Protocol Specification
  • Message Format
• Setup
  • Installing Dependencies
  • Running Tests
  • Contributing

Architecture

Contracts

Descriptions

Exchange.sol

Exchange contains all business logic associated with executing trades and cancelling orders. Exchange accepts orders that conform to 0x 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 MultiSigWalletWithTimeLock, 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).

MultiSigWalletWithTimeLock.sol

MultiSigWalletWithTimeLock is a temporary placeholder contract that will be replaced by a thoroughly researched, tested and audited DAO. MultiSigWalletWithTimeLock is based upon the MultiSigWallet contract developed by the Gnosis team, but with an added mandatory time delay between when a proposal is approved and when that proposal may be executed. This speed bump ensures that the multi sig owners cannot conspire to push through a change to 0x protocol without end users having sufficient time to react. MultiSigWalletWithTimeLock is the only entity with permission to grant or revoke access to the Proxy and, by extension, ERC20 token allowances. MultiSigWalletWithTimeLock is assigned as the owner of Proxy and, once a suitable DAO is developed, MultiSigWalletWithTimeLock 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.

Deployed Addresses

Kovan

• Exchange.sol: 0xed97b186ee3bae12a3fe6a9fb55300b5630a1b4c
• Proxy.sol: 0x946a1c437fb5a61bd5c95416346e684c802c5d2a
• MultiSigWalletWithTimeLock.sol: 0xa9a207b3df3f0d3ca33acf399e9af5db5902db39
• TokenRegistry.sol: 0x0fea265f59495859467e648ec99a87549aa6ede0

Protocol Specification

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).
salt	uint256	Arbitrary number that allows for uniqueness of the order's Keccak SHA3 hash.
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

Installing Dependencies

Install Node v6.9.1

Install ethereumjs-testrpc

npm i -g ethereumjs-testrpc@^3.0.2

Install project dependencies:

npm install

Running Tests

Start Testrpc

testrpc --networkId 50

Compile contracts

npm run compile

Run tests

npm run test

Contributing

Coding conventions

We use a custom set of TSLint rules to enforce our coding conventions.

In order to see style violation errors, install a tslinter for your text editor. e.g Atom's atom-typescript.