eip-712
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Tiny library with utility functions that can help with signing and verifying EIP-712 based messages
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# `eip-712`
  [](https://github.com/Mrtenz/eip-712/actions) [](https://codecov.io/gh/Mrtenz/eip-712)
This is a library for Node.js and web browsers with some utility functions that can help with signing and verifying [EIP-712](https://eips.ethereum.org/EIPS/eip-712) based messages. It is fully written in TypeScript, and is currently only compatible with the latest specification of EIP-712 ([eth_signTypedData_v4](https://docs.metamask.io/guide/signing-data.html#sign-typed-data-v4)).
https://eips.ethereum.org/EIPS/eip-712
Note that this library currently does not handle the signing itself. For this, you can use something like Ethers.js or ethereumjs-util. For examples, please see the [`examples`](https://github.com/Mrtenz/eip-712/blob/master/examples) folder.
## Installation
You can install this library with Yarn or NPM:
```
$ yarn add eip-712
```
```
$ npm install eip-712
```
There is a CommonJS version as well as an ES6 version available. Most tools should automatically pick the right version (e.g. Node.js, Webpack).
### Getting Started
First, define your typed data as a JSON object, according to the JSON schema specified by EIP-712. For example:
```json
{
"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!"
}
}
```
### Functions
Here is a brief description of the functions available in this library. For more detailed examples, you can refer to [`src/eip-712.test.ts`](https://github.com/Mrtenz/eip-712/blob/master/src/eip-712.test.ts), or to the examples in the [`examples`](https://github.com/Mrtenz/eip-712/blob/master/examples) folder.
#### `getMessage(typedData, hash?)`
This function will return the full EIP-191 encoded message to be signed as Buffer, for the typed data specified. If `hash` is enabled, the message will be hashed using Keccak256.
```js
import { getMessage } from 'eip-712';
const typedData = { /*...*/ };
console.log(getMessage(typedData).toString('hex')); // 1901f2cee375fa42b42143804025fc449deafd50cc031ca257e0b194a650a912090fc52c0ee5d84264471806290a3f2c4cecfc5490626bf912d01f240d7a274b371e
console.log(getMessage(typedData, true).toString('hex')); // be609aee343fb3c4b28e1df9e632fca64fcfaede20f02e86244efddf30957bd2
```
#### `asArray(typedData)`
This function returns the typed data as an array. This can be useful for encoding typed data as ABI.
```js
import { asArray } from 'eip-712';
const typedData = { /*...*/ };
console.log(asArray(typedData)); // [ ['Cow', '0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826'], ['Bob', '0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB'], 'Hello, Bob!' ]
```
#### `getStructHash(typedData, type, data)`
This function returns a Keccak-256 hash for a single struct type (e.g. EIP712Domain, Person or Mail).
```js
import { getStructHash } from 'eip-712';
const typedData = { /*...*/ };
console.log(getStructHash(typedData, 'EIP712Domain', typedData.domain).toString('hex')); // f2cee375fa42b42143804025fc449deafd50cc031ca257e0b194a650a912090f
```
#### `encodeData(typedData, type, data)`
This function returns the raw ABI encoded data for the struct type.
```js
import { encodeData } from 'eip-712';
const typedData = { /*...*/ };
console.log(encodeData(typedData, 'EIP712Domain', typedData.domain).toString('hex')); // 8b73c3c69bb8fe3d512ecc4cf759cc79239f7b179b0ffacaa9a75d522b39400fc70ef06638535b4881fafcac8287e210e3769ff1a8e91f1b95d6246e61e4d3c6c89efdaa54c0f20c7adf612882df0950f5a951637e0307cdcb4c672f298b8bc60000000000000000000000000000000000000000000000000000000000000001000000000000000000000000cccccccccccccccccccccccccccccccccccccccc
```
#### `getTypeHash(typedData, type)`
This function returns the type hash for a struct type. This is the same as `Keccak256(EIP712Domain(string name,string version,uint256 chainId,address verifyingContract))`, with optional sub-types automatically included too.
```js
import { getTypeHash } from 'eip-712';
const typedData = { /*...*/ };
console.log(getTypeHash(typedData, 'EIP712Domain').toString('hex')); // 8b73c3c69bb8fe3d512ecc4cf759cc79239f7b179b0ffacaa9a75d522b39400f
```
#### `encodeType(typedData, type)`
This function returns the type before hashing it, e.g. `EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)`, with optional sub-types automatically included too.
```js
import { encodeType } from 'eip-712';
const typedData = { /*...*/ };
console.log(encodeType(typedData, 'EIP712Domain')); // EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)
```
#### `getDependencies(typedData, type)`
This function returns all sub-types used by a struct as a string array. If the struct has no sub-types (like `EIP712Domain`), an array with only the type itself is returned.
```js
import { getDependencies } from 'eip-712';
const typedData = { /*...*/ };
console.log(getDependencies(typedData, 'EIP712Domain')); // ['EIP712Domain']
console.log(getDependencies(typedData, 'Mail')); // ['Mail', 'Person']
```
### Non-standard domains (e.g., CIP-23)
It's possible to use a custom domain format, like from the CIP-23 specification, or to disable verifying the domain format completely, if you want to use a custom implementation of EIP-712.
To do this, you can pass options to each function, as last parameter. For example, in order to get the message hash for a message, you can do the following:
```ts
import { getMessage } from 'eip-712';
import type { Options } from 'eip-712';
const typedData = { /*...*/ };
const options: Options = {
// A custom domain identifier. Defaults to 'EIP712Domain'.
domain: 'CIP23Domain',
// Whether to verify the structure of the domain. Defaults to 'true'.
verifyDomain: false
};
console.log(getMessage(typedData, true, options).toString('hex'));
```