Crate jwt_simple

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A new JWT implementation for Rust that focuses on simplicity, while avoiding common JWT security pitfalls.

jwt-simple is unopinionated and supports all commonly deployed authentication and signature algorithms:

  • HMAC-SHA2:
    • HS256
    • HS384
    • HS512
  • RSA
    • RS256
    • RS384
    • RS512
    • PS256
    • PS384
    • PS512
  • p256
    • ES256
  • p384
    • ES384
  • secp256k1
    • ES256K
  • Ed25519
    • EdDSA

jwt-simple can be compiled out of the box to WebAssembly/WASI. It is fully compatible with Fastly Compute service.

Important: JWT’s purpose is to verify that data has been created by a party knowing a secret key. It does not provide any kind of confidentiality: JWT data is simply encoded as BASE64, and is not encrypted.



jwt-simple = "0.12"


use jwt_simple::prelude::*;

§Authentication (symmetric, HS* JWT algorithms) example

Authentication schemes use the same key for creating and verifying tokens. In other words, both parties need to ultimately trust each other, or else the verifier could also create arbitrary tokens.

§Keys and tokens creation

Key creation:

use jwt_simple::prelude::*;

// create a new key for the `HS256` JWT algorithm
let key = HS256Key::generate();

A key can be exported as bytes with key.to_bytes(), and restored with HS256Key::from_bytes().

Token creation:

/// create claims valid for 2 hours
let claims = Claims::create(Duration::from_hours(2));
let token = key.authenticate(claims)?;

-> Done!

§Token verification

let claims = key.verify_token::<NoCustomClaims>(&token, None)?;

-> Done! No additional steps required.

Key expiration, start time, authentication tags, etc. are automatically verified. The function fails with JWTError::InvalidAuthenticationTag if the authentication tag is invalid for the given key.

The full set of claims can be inspected in the claims object if necessary. NoCustomClaims means that only the standard set of claims is used by the application, but application-defined claims can also be supported.

Extra verification steps can optionally be enabled via the ValidationOptions structure:

let mut options = VerificationOptions::default();
// Accept tokens that will only be valid in the future
options.accept_future = true;
// Accept tokens even if they have expired up to 15 minutes after the deadline
// and/or they will be valid within 15 minutes.
options.time_tolerance = Some(Duration::from_mins(15));
// Reject tokens if they were issued more than 1 hour ago
options.max_validity = Some(Duration::from_hours(1));
// Reject tokens if they don't include an issuer from that list
options.allowed_issuers = Some(HashSet::from_strings(&["example app"]));
// See the documentation for the full list of available options

let claims = key.verify_token::<NoCustomClaims>(&token, Some(options))?;

Note that allowed_issuers and allowed_audiences are not strings, but sets of strings (using the HashSet type from the Rust standard library), as the application can allow multiple return values.

§Signatures (asymmetric, RS*, PS*, ES* and EdDSA algorithms) example

A signature requires a key pair: a secret key used to create tokens, and a public key, that can only verify them.

Always use a signature scheme if both parties do not ultimately trust each other, such as tokens exchanged between clients and API providers.

§Key pairs and tokens creation

Key creation:

use jwt_simple::prelude::*;

// create a new key pair for the `ES256` JWT algorithm
let key_pair = ES256KeyPair::generate();

// Or the `ES384` JWT algorithm
let key_pair = ES384KeyPair::generate();

// a public key can be extracted from a key pair:
let public_key = key_pair.public_key();

Keys can be exported as bytes for later reuse, and imported from bytes or, for RSA, from individual parameters, DER-encoded data or PEM-encoded data.

RSA key pair creation, using OpenSSL and PEM importation of the secret key:

openssl genrsa -out private.pem 2048
openssl rsa -in private.pem -outform PEM -pubout -out public.pem
let key_pair = RS384KeyPair::from_pem(private_pem_file_content)?;
let public_key = RS384PublicKey::from_pem(public_pem_file_content)?;

Token creation and verification work the same way as with HS* algorithms, except that tokens are created with a key pair, and verified using the corresponding public key.

Token creation:

/// create claims valid for 2 hours
let claims = Claims::create(Duration::from_hours(2));
let token = key_pair.sign(claims)?;

Token verification:

let claims = public_key.verify_token::<NoCustomClaims>(&token, None)?;

Available verification options are identical to the ones used with symmetric algorithms.

§Advanced usage

§Custom claims

Claim objects support all the standard claims by default, and they can be set directly or via convenient helpers:

let claims = Claims::create(Duration::from_hours(2))
    .with_issuer("Example issuer")
    .with_subject("Example subject");

But application-defined claims can also be defined. These simply have to be present in a serializable type (this requires the serde crate):

#[derive(Serialize, Deserialize)]
struct MyAdditionalData {
    user_is_admin: bool,
    user_country: String,
let my_additional_data = MyAdditionalData {
    user_is_admin: false,
    user_country: "FR".to_string(),

// Claim creation with custom data:

let claims = Claims::with_custom_claims(my_additional_data, Duration::from_secs(30));

// Claim verification with custom data. Note the presence of the custom data type:

let claims = public_key.verify_token::<MyAdditionalData>(&token, None)?;
let user_is_admin = claims.custom.user_is_admin;

§Peeking at metadata before verification

Properties such as the key identifier can be useful prior to tag or signature verification in order to pick the right key out of a set.

let metadata = Token::decode_metadata(&token)?;
let key_id = metadata.key_id();
let algorithm = metadata.algorithm();
// all other standard properties are also accessible

§Creating and attaching key identifiers

Key identifiers indicate to verifiers what public key (or shared key) should be used for verification. They can be attached at any time to existing shared keys, key pairs and public keys:

let public_key_with_id = public_key.with_key_id(&"unique key identifier");

Instead of delegating this to applications, jwt-simple can also create such an identifier for an existing key:

let key_id = public_key.create_key_id();

This creates an text-encoded identifier for the key, attaches it, and returns it.

If an identifier has been attached to a shared key or a key pair, tokens created with them will include it.



  • The Error type, a wrapper around a dynamic error type.