feature request: 2FA

[pnyda]

Now that Rabby has both a browser extension and a mobile app, It would be awesome if we could have a 2FA implementaion based on threshold signing. e.g.

1. Split a ECDSA key into 2 shares.
2. browser extension stores one share.
3. phone app stores other one.
4. The two communicates via MPC and generate a valid signature.

This way approving a transaction via 2FA needs no additional gas cost, as opposed to something like Safe multisig, since 2FA authentication logic is handled off-chain.

Benefits of 2FA

Currently, when someone steals my laptop, he could steal all my coins. 2FA wallets can mitigate this risk.

Schemes we could use

Lindell17 https://eprint.iacr.org/2017/552
GG18 https://ethresear.ch/t/fast-multiparty-threshold-ecdsa-possible-on-ethereum-today/5524