VIP: Signed Structs (EIP 712 Support)

Simple Summary

Allow defining a struct that contains a signature field such that there is a standard algorithm for performing ecrecover on it. Would be most useful with #1019

Abstract

In constructions like Plasma, it is often useful to define a transaction data structure to manage the complexity of a transaction type and how it is used to validate logic in the contract. Having a struct type that can define an extra signature field which can be processed in a standard algorithm to recover the signer of the transaction would be very helpful to streamline the design of these algorithms without too much complexity in the contract.

Motivation

We want to make working with different constructions like Plasma as simple and expressive as possible. Primatives like working with signed transactions are very commonplace in this constructions, and we should support primitives like this as first class citizens to make it easier and safer to write these kinds of contracts.

Specification

We might define a structure as follows that contains a VRS signature with which recovery of the signing address can be performed via exclusion of the signature, hashing of the rest of the struct as an RLP encoded object, and performing ecrecover(hash, r, s, v) of the result. The field that would contain this signature in this special struct would be denoted by __sig__ . get_signer(struct) would be the function that performed this function to return the signer's address.

struct Transaction:
    a: address
    b: uint256
    __sig__: VRS_SECP256K1  # Special type representing a VRS signature for a Secp256k1 signature
...

# Assert that the transaction's signer is the caller here.
assert get_signer(transaction) == msg.sender
...

There might potentially be defined a custom type to represent a VRS signature, but should be extensible with other types for other signature methods that may be included later.

Backwards Compatibility

This would be fully backwards compatible as it is a new featureset that would be added.

Copyright

Copyright and related rights waived via CC0