Purpose

Build a well designed and scalable backend architecture, in the form of a multisig wallet.

The assessment

• Design and implement a secure multi-sig wallet contract:
• Define the number of signatories required to execute a transaction (e.g. 2 out of 3).
• Define the list of signatories and their addresses.
• Implement the functionality to add/remove signatures.
• Implement the functionality to execute a transaction after the required number of signatures have been obtained.
• Implement the functionality to cancel a transaction before it has been executed.

Extra points for:

• Implementing a way to recover the wallet in case of loss of private keys.
• Support for WebAuthn (FIDO2) as a second factor of authentication for signing transactions.
• Access control for actions that can be taken by signatories (e.g. add/remove signatories, execute/cancel transactions).

Stack

Deployment in any EVM based blockchain (e.g. Ethereum, Binance Smart Chain, Polygon, etc) is fine.

Taylor's notes

I think I covered every point except support for WebAuthn, although it uses a SHA256 hashing algorithm. This is the same way I've implemented the wallet recovery functionality, so I believe it wouldn't be a big stretch to extend this for WebAuthn support!

For access control I've just assigned a "level" to each address we add to the wallet, 1 being admin controls, anything higher is custom or could be customised further. The contract can function fine without having an admin account set, leaving it fully decentralised.

For deployment I just created a version which includes 3 test wallets I own. The idea for production would be to use the factory contract to produce as many as we want at scale.

I've added some events and hooked it up so a graph deployment, as I think this could be a better way of storing the list of addresses for gas savings.

Deployed and verified here on Goerli: https://goerli.etherscan.io/address/0x72234D530C7dC5888776a2BD812775D2Fd02a167

Graph: https://thegraph.com/hosted-service/subgraph/taylorferran/openfort-multisig

Functionality includes:

• Defining signatories, signatory roles and inital amount of signatures required. Done on contract creation.
• Create transactions if a signatory. Inserting the deposit address and deposit amount.
• Sign transactions if a signatory.
• Unsign transactions if a signatory.
• If transaction signatures reaches 0, transaction is sent out to the deposit address.
• Cancel transactions if the address calling it is signatory level two or below.
• Update number of signatures needed if the address calling it is signatory level one.
• Add a signatory if the address calling it is signatory level one.
• Remove a signatory if the address calling it is signatory level one.
• Assign a password hash to an address.
• Sign a transaction using the password for that address (for recovery purposes).

Main functionality unit tested, would need expanded for edge cases.

Tested included and passing:

• Create a transaction as a signatory (1104ms)
• Can't create a transaction if not a signatory (52ms)
• Can sign a transaction if a signatory and transaction processes (78ms)
• Can unsign a transaction (67ms)
• Can cancel a transaction only if level 2 or above (52ms)
• Change number of signers if account level 1 (38ms)
• Add a signatory (41ms)
• Remove a signatory