# `PublicKey`

An Ed25519 public key: 32 bytes as Base64url.

Use it to check a signature with `crypto.verify_signature`. It isn't secret, so it may be stored and sent. For a token's key from a provider, use [`Jwk`](/docs/types/type-jwk.md).

## Shape

One value, held as text in one set form, with no parts: `PUAXw-hDiVqStwqnTRt-vJyYLM8uxJaMwM1V8Sr0Zgw`.

## Example

```jadpo
PublicKey("11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo")
```

`PublicKey(raw)` checks the text, and text that isn't one breaks the `format` rule.

`text.parse(raw, as: PublicKey)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`.

This operation gives one: `crypto.public_key`.

## Good to know

- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.

## In JSON

A string, in a request, a response or `json.write`:

```json
"11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo"
"PUAXw-hDiVqStwqnTRt-vJyYLM8uxJaMwM1V8Sr0Zgw"
```

## Details

<details>
<summary>Text form, storage, how it is shown, and operations</summary>

`PublicKey` is in the group Security, and has been in Jadpo since 0.1.0.

### Text form

`text.from` writes one standard text form, the same form `text.parse` reads back: `11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo` and `PUAXw-hDiVqStwqnTRt-vJyYLM8uxJaMwM1V8Sr0Zgw`.

### How it is stored

It is stored in one column named for the field, of type `text`. `PUAXw-hDiVqStwqnTRt-vJyYLM8uxJaMwM1V8Sr0Zgw` is stored as `'PUAXw-hDiVqStwqnTRt-vJyYLM8uxJaMwM1V8Sr0Zgw'`.

### How it is shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo` | `11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo` |
| `PUAXw-hDiVqStwqnTRt-vJyYLM8uxJaMwM1V8Sr0Zgw` | `PUAXw-hDiVqStwqnTRt-vJyYLM8uxJaMwM1V8Sr0Zgw` |

### Operations

- `crypto.public_key(key: PrivateKey) -> PublicKey`: The Ed25519 public key of the `PrivateKey` setting, which isn't secret: published, others check what the app signs with it.
- `crypto.verify_signature(value: T, signature: Bytes, key: PublicKey) -> Bool`: Whether `signature` is `value`'s Ed25519 signature under `key`, which is not secret and may be read.

It also takes `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. [How every standard type behaves](/docs/every-standard-type-meets-one-contract.md) says how they work.

</details>