> For the complete documentation index, see [llms.txt](https://docs.aeternity.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aeternity.com/developer-documentation/aepp-sdk-js/docs/guides/typed-data.md).

# Typed data hashing and signing

## Common structure

The whole idea is heavily inspired by [EIP-712](https://eips.ethereum.org/EIPS/eip-712#definition-of-domainseparator). To get a signature needed to calculate `hash(hash(domain), hash(aci), hash(data))`.

`hash` function is `blake2b`.

`domain` is a record containing not required properties:

* `name` as string,
* `version` as integer,
* `networkId` as string,
* `contractAddress` as ct-encoded string.

`aci` is part of a complete contract ACI. It defines a type of data to sign. For example, the ACI

```json
{
  "record": [
    { "name": "foo", "type": "string" },
    { "name": "bar", "type": "int" }
  ]
}
```

corresponds to the data

```json
{ "foo": "test", "bar": 42 }
```

`domain` and `data` are fate-encoded before hashing. `aci` is prepared for hashing according to [RFC8785](https://tools.ietf.org/html/rfc8785).

## Implementation

* [AccountBase:signTypedData](https://github.com/aeternity/aepp-sdk-js/blob/1cd128798018d98bdd41eff9104442b44b385d46/src/account/Base.ts#L64-L71) — calculates signature, supported in AccountMemory and in aepp-wallet connection;
* [hashTypedData](https://github.com/aeternity/aepp-sdk-js/blob/1cd128798018d98bdd41eff9104442b44b385d46/src/utils/typed-data.ts#L87-L101) — calculates the overall hash of typed data to sign;
* [hashJson](https://github.com/aeternity/aepp-sdk-js/blob/1cd128798018d98bdd41eff9104442b44b385d46/src/utils/typed-data.ts#L11-L13) — deterministic hashing of an arbitrary JS value, used to calculate `hash(aci)`;
* [hashDomain](https://github.com/aeternity/aepp-sdk-js/blob/1cd128798018d98bdd41eff9104442b44b385d46/src/utils/typed-data.ts#L58-L82) — use for debugging or to prepare the hash value for smart contract.

## Examples

* [signing and verifying on aepp side](https://github.com/aeternity/aepp-sdk-js/blob/1cd128798018d98bdd41eff9104442b44b385d46/examples/browser/aepp/src/TypedData.vue)
* [signing confirmation on wallet side](https://github.com/aeternity/aepp-sdk-js/blob/1cd128798018d98bdd41eff9104442b44b385d46/examples/browser/wallet-iframe/src/App.vue#L168-L176)
* [verifying a signature on contract side](https://github.com/aeternity/aepp-sdk-js/blob/1cd128798018d98bdd41eff9104442b44b385d46/test/integration/typed-data.ts#L76-L106)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.aeternity.com/developer-documentation/aepp-sdk-js/docs/guides/typed-data.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.