Crate eip_712

EIP-712 encoding utilities

Specification

encode(domainSeparator : 𝔹²⁵⁶, message : 𝕊) = "\x19\x01" ‖ domainSeparator ‖ hashStruct(message)

• data adheres to 𝕊, a structure defined in the rigorous eip-712
• \x01 is needed to comply with EIP-191
• domainSeparator and hashStruct are defined below

A) domainSeparator

domainSeparator = hashStruct(eip712Domain)

Struct named EIP712Domain with the following fields

• name: String
• version: String
• chain_id: U256,
• verifying_contract: H160
• salt: Option<H256>

C) hashStruct

hashStruct(s : 𝕊) = keccak256(typeHash ‖ encodeData(s))
typeHash = keccak256(encodeType(typeOf(s)))

i) encodeType

• name ‖ "(" ‖ member₁ ‖ "," ‖ member₂ ‖ "," ‖ … ‖ memberₙ ")"
• each member is written as type ‖ " " ‖ name
• encodings cascade down and are sorted by name

ii) encodeData

• enc(value₁) ‖ enc(value₂) ‖ … ‖ enc(valueₙ)

• each encoded member is 32-byte long

  a) atomic

  • boolean => U256
  • address => H160
  • uint => sign-extended U256 in big endian order
  • bytes1:31 => H@256

  b) dynamic

  • bytes => keccak256(bytes)
  • string => keccak256(string)

  c) referenced

  • array => keccak256(encodeData(array))
  • struct => rec(keccak256(hashStruct(struct)))

D) Example

Query

{
  "jsonrpc": "2.0",
  "method": "eth_signTypedData",
  "params": [
    "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826",
    {
      "types": {
        "EIP712Domain": [
          {
            "name": "name",
            "type": "string"
          },
          {
            "name": "version",
            "type": "string"
          },
          {
            "name": "chainId",
            "type": "uint256"
          },
          {
            "name": "verifyingContract",
            "type": "address"
          }
        ],
        "Person": [
          {
            "name": "name",
            "type": "string"
          },
          {
            "name": "wallet",
            "type": "address"
          }
        ],
        "Mail": [
          {
            "name": "from",
            "type": "Person"
          },
          {
            "name": "to",
            "type": "Person"
          },
          {
            "name": "contents",
            "type": "string"
          }
        ]
      },
      "primaryType": "Mail",
      "domain": {
        "name": "Ether Mail",
        "version": "1",
        "chainId": 1,
        "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
      },
      "message": {
        "from": {
          "name": "Cow",
          "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
        },
        "to": {
          "name": "Bob",
          "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
        },
        "contents": "Hello, Bob!"
      }
    }
  ],
  "id": 1
}

Response

{
  "id":1,
  "jsonrpc": "2.0",
  "result": "0x4355c47d63924e8a72e509b65029052eb6c299d53a04e167c5775fd466751c9d07299936d304c153f6443dfa05f40ff007d72911b6f72307f996231605b915621c"
}

Structs

EIP712

EIP-712 struct

Error

Error type

Enums

ErrorKind

Possible errors encountered while hashing/encoding an EIP-712 compliant data structure

Functions

hash_structured_data

encodes and hashes the given EIP712 struct