🗝️ EIP-712: Typed Structured Data Hashing and Signing

EIP-712 is a standard for structuring typed data for Ethereum smart contracts. It is a standard for how to encode typed data according to EIP-191 so that the encoded data may be used to produce a cryptographic hash and a signature.

Motivation

There are many use cases where it is useful to allow a smart contract to verify that a message was signed by a known account. This is useful for cases such as signed approvals, price oracles, and authenticated off-chain protocols.

The Ethereum ABI specification does not provide encoding for structs, making it difficult to encode arbitrary data for signing. This EIP provides a basic specification for encoding typed data.

Specification

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Definitions

• domain is a set of information about the context in which the message is being signed. It is encoded as a struct with the following members:
  • name is a string that describes the domain to which the message is being sent. This string SHOULD be the human-readable name of the domain.
  • version is a string that represents the version of the domain's message signing format. This string SHOULD be a unique identifier for the version of the domain's message signing format.
  • chainId is a 256-bit integer that represents the chain ID of the chain where the message is being sent.
  • verifyingContract is a 160-bit integer that represents the address of the contract that will be used to verify the message.
  • salt is a 256-bit integer that represents a random value used to ensure that signatures are unique to this message.
• message is a struct that contains the information to be signed. It is encoded as a struct.