# JWT

The JWT module lets you encode, decode and verify Json Web Tokens easily!

```cpp
start:
  do payload = {
    "user": "name",
    "somekey": {
      "somevalue": 42
    },
    "exp": 1618064023,
    "iss": "CSML STUDIO"
  }

  do jwt = JWT(payload).sign("HS256", "SECRET_KEY")
  say jwt

  do decoded = JWT(jwt).decode("HS256", "SECRET_KEY")
  say "{{decoded}}"

  do claims = {
    "iss": "CSML STUDIO"
  }
  do verified = JWT(jwt).verify(claims, "HS256", "SECRET_KEY")
  say "{{verified}}"
```

## Methods

### sign

**exemple:** `JWT(data).sign(algorithm, secret)`

* `data`: json object to sign and convert to a JWT token
* `algorithm`: see below
* `secret`: a secret string used to sign the JWT

This method returns a properly encoded JWT as a string.

### decode

**exemple:** `JWT(token).decode(algorithm, secret)`

* `token`: the token to decode

**Note:** `decode` does not try to verify that the token is valid. It simply decodes its payload back to the original form.

This method returns the full JWT data, in the form:`{ "payload": { ... your data }, "headers": { "alg": ALG, "typ": "JWT" }}`

### verify

**exemple:** `JWT(token).verify(claims, algorithm, secret)`

* `claims`: set of claims (in JSON form) to verify the JWT against

**Note:** only valid claims are verified. See the list of official claims in the JWT specs [here](https://www.iana.org/assignments/jwt/jwt.xhtml#claims).

This method returns the full JWT data, in the form:`{ "payload": { ... your data }, "headers": { "alg": ALG, "typ": "JWT" }}`

## Supported algorithms

JWT supports the following algorithms: `HS256`, `HS384`, `HS512` (corresponding to HMAC using SHA-256, SHA-384 and SHA-512 respectively).

The secret key must be a valid, url-safe string.

## Error handling

When a sign, decode or verify operation fails, `Null` is returned and a `say Error(error_message)` is emitted.


---

# Agent Instructions: Querying This Documentation

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

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.csml.dev/language/standard-library/crypto/jwt.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.