About stablecoin.services

Today, we are introducing stablecoin.services, which allows for common Dai and Chai operations to be performed gas-free, at your convenience. This promotes Dai and Chai to first class tokens in the Ethereum network, allowing users to transact in these currencies without ever holding any Ether.

At launch, the following operations are supported:

• Dai and Chai transfers,
• Dai -> Eth and Chai -> Eth uniswap trades,
• Dai <-> Chai conversions.

Head over to stablecoin.services to give it a spin. Alfred will be there to assist you.

A relaying api is provided at api.stablecoin.services, which can be integrated into other dapps interested in offering gas-free conveniences to their users.

How does it work?

To initiate an action, the user signs a message specifying the details of the operation to be performed, and authorizes a relayer to process the transaction on their behalf. As the relayer submits the message to the blockchain, the operation is processed and the fee is delivered to the relayer to reimburse their gas costs.

At the heart of this process sits a smart contract called the Dai Automated Clearing House, or dach, for short. The first time you use stablecoin.services you will be asked to sign a message which permits this contract to operate on your behalf. You should study this contract carefully as it determines the terms of engagement between you and the relaying service. It specifies a set of message types, one for each action offered by stablecoin.services, and corresponding functions which executes the operation specified by each message.

This is all made possible by the permit function in the Dai and Chai contracts, which allows for approvals to be done by signed messages, instead of transactions relying on msg.sender. We hope that stablecoin.services serves as an example of the power and extensibility of the permit construction, and encourage future token designers to adopt a similar pattern.

The processing fee suggested by the front end is calculated according to the following formula:

operation_fee = 1.1 * gas_per_operation * fast_gas_price * eth_price_in_dai (or chai),

where fast_gas_price is provided by Gas Station Network.

What are the risks?

The dach contract has not yet undergone an audit. It is a fairly small and straightforward contract written and reviewed by experienced smart contract developers, but as with all smart contracts, you should make your own risk assessment before engaging.

Assuming the contract works as intended, neither the relayer or the dach contract holds custody over any user assets. They are simply granted the permission to execute the actions as specified by the signed messages by the user, and the worst they can do is to withhold from processing an operation, only to submit it when the user gives up. To mitigate against this, messages are equipped with an expiration date after which they can no longer be processed. The time to live for messages signed using stablecoin.services is 10 minutes. Messages are also equipped with a nonce for replay protection and to enable overwriting of stale messages.

Resources

The code for the dach contract can be found at github.com/dapphub/ds-dach, or in the etherscan live deployment

The code for the stablecoin.services front end is hosted at github.com/MrChico/stablecoin.services.

Both distributed under the AGPL license.

Pixel Art by Abbey Titcomb

Documentation of the relaying api is provided at api.stablecoin.services

Martin Lundfall, Andrew Cassetti, Lev Livnev