# RFC7638: JSON Web Key (JWK) Thumbprint

New in version v0.15.

## authlib.jose

JOSE implementation in Authlib. Tracking the status of JOSE specs at https://tools.ietf.org/wg/jose/

This RFC7638 is used for computing a hash value over a JSON Web Key (JWK). The value can be used as an identity of the JWK.

The `.thumbprint` method is defined on the `Key` class, you can use it directly:

    from authlib.jose import JsonWebKey

    raw = read_file('rsa.pem')
    key = JsonWebKey.import_key(raw)

    key.thumbprint()

If a key has no `kid`, you can add the value of `.thumbprint()` as a kid:

    key['kid'] = key.thumbprint()

This method is available on every Key class, including `OctKey`, `RSAKey`, `ECKey`, and `OKPKey`.