Implement Ethereum compatible signatures

[facundomedica]

Context

This would allow users to also use Ethereum wallets (like Metamask) to interact with Cosmos SDK chains.

Related:
#13787

Overview

It would work as follows:

1. A user connects its wallet and is requested to sign a message like "Get CosmosHub address".
2. The app gets the user's public key from the signature and derives the Cosmos address
3. When the user wants to send a tx it will be prompted with a human readable display of the transaction.

Important: this human readable display is the message that's going to get signed, so we need to make sure to include all necessary details so then we can verify it in the SDK.

Alternatives

EIP 191

See here

It's the simplest form in which an app can request a signature for an arbitrary message. We can use new lines, or any kind of formatted text.

This is how Secret is doing it. They use Amino's StdDoc as the message (pretty JSON).

Pros:

• easier to read
• is being shown "as is" on Ledger (up to a certain amount of characters).

Cons:

• Less structured format

EIP 712

See here

It's the latest standard for structured data hashing and signing.

Evmos seems to be using this with Amino (pending research).

Pros:

• in some wallets, it's being shown in a structured manner (screenshot). In others, it just displays an unformatted JSON.

Cons:

• Doesn't show up "as is" on Ledger and is not human readable on it too. You get a domain hash and a message hash; these are not shown on the browser (so I don't know if there's a way to know for sure if what you are signing is what you are intending to sign).
• Might be inconsistent while displaying on browser (Point 1 of "Pros")
• The structure is designed for EVM types, so we might encounter some issues

Proposal

Implement a EIP191 signature handling mechanism with a struct containing all the necessary details to make it human readable + machine verifiable. Something like a YAML (or any other readable format) would work in which the readable part is at the beginning and then at the end we can append hashes, tx body bytes, and whatever we might need.

This will also require work on CosmJS. We could borrow some stuff from https://github.com/scrtlabs/secret.js

Questions

• Is it possible to use something else other than Amino's StdDoc to get the sign bytes?

[tac0turtle]

CC @assafmo @fedekunze

[assafmo]

Hi, happy to help. For EIP191 anything textual will do. Here's how it currently looks on Secret (on mobile too):

[assafmo]

And here's our signer implementation: https://github.com/scrtlabs/secret.js/blob/master/src/wallet_metamask.ts

[pyramation]

Following ⚛️🦊

and will track for FE tooling here cosmology-tech/cosmos-kit#85

[facundomedica]

Right now we are blocked by #11970 and its implementation on the js side cosmos/cosmjs#1147.
Using the textual value renderers will allow us to get nicer human readable messages to sign.