Some facts about EIP 712

Before diving into thetechnicalities, it's essential to understand the problem EIP-712 solves. Intraditional Ethereum transactions and interactions, users are often required tosign messages to prove ownership of an account. Before EIP-712, this signingwas done on arbitrary data, which could be confusing and potentially risky, asit's hard to verify what exactly is being signed. This can often lead tomalicious actors exploiting this and stealing tokens from victim's wallets.

EIP-712 solves this byintroducing a standard for signing data that is both structured and typed. Thismeans that the data being signed is organized in a specific way and that eachpiece of data is associated with a type (e.g., string, uint, etc.). This structuredapproach allows for the data to be displayed in a more user-friendly manner,making it clearer what the signer is agreeing to.

How It Works

EIP-712 introduces a methodfor creating a domain separator, a unique identifier for a smart contract thatprevents signed messages from being valid across different contractsunintentionally. It also defines a way to hash structured data in a manner thatis consistent across platforms.

Here’s a brief overview ofthe process:

Define the Data Types: Thefirst step in implementing EIP-712 is to define the data types that will beused. This is done by creating a JSON schema that describes the types andstructures of the data.

Create a Domain Separator:The domain separator is a hash that uniquely identifies a smart contract'sdomain, including the contract name, version, and the network it's on. Thisprevents signatures from being valid across different domains.

Hash the Structured Data:Once the data types are defined, the structured data can be hashed using aspecific method defined in EIP-712. This hashed data can then be signed by auser's address.

Solidity Example

Implementing EIP-712 in aSolidity smart contract involves several steps. Below is a simplified exampleto illustrate the process:

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In this example, a structnamed MyData is defined, containing an id, a message, and the sender's address.The contract inherits from OpenZeppelin's EIP712 implementation, setting up adomain separator in the constructor. The hashAndSign function then demonstrateshow to hash the data according to EIP-712 standards, preparing it for signing.

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