Swap: A Peer-to-Peer Protocol for Trading Ethereum Tokens

We present a peer-to-peer methodology for trading ERC20 tokens on the Ethereum blockchain. First, we outline the limitations of blockchain order books and offer a strong alternative in peer-to-peer token trading: off-chain negotiation and on-chain settlement. We then describe a protocol through which parties are able to signal to others their intent to trade tokens. Once connected, counterparties freely communicate prices and transmit orders among themselves. Finally we present an Ethereum smart contract to fill orders on the Ethereum blockchain.

Source: https://swap.tech/whitepaper