.. index:: single: jwt_jwa .. _jwt_jwa/0:

.. rst-class:: right

object

jwt_jwa

JSON Web Algorithm metadata and header helpers.

| Availability: | logtalk_load(jwt(loader))

| Author: Paulo Moura | Version: 1:0:0 | Date: 2026-07-06

| Compilation flags: | static, context_switching_calls

| Imports: | public :ref:`jwt_helpers <jwt_helpers/0>` | Uses: | :ref:`list <list/0>`

| Remarks: | (none)

| Inherited public predicates: |  :ref:`options_protocol/0::check_option/1`  :ref:`options_protocol/0::check_options/1`  :ref:`options_protocol/0::default_option/1`  :ref:`options_protocol/0::default_options/1`  :ref:`options_protocol/0::option/2`  :ref:`options_protocol/0::option/3`  :ref:`options_protocol/0::valid_option/1`  :ref:`options_protocol/0::valid_options/1`  

.. contents:: :local: :backlinks: top

Public predicates

.. index:: header_algorithm/2 .. _jwt_jwa/0::header_algorithm/2:

header_algorithm/2 ^^^^^^^^^^^^^^^^^^^^^^

Extracts and validates the JWT header algorithm.

| Compilation flags: | static

| Template: | header_algorithm(Header,Algorithm) | Mode and number of proofs: | header_algorithm(+term,-atom) - one_or_error

| Exceptions: | Header does not contain a valid alg member: | domain_error(jwt_header,Header)

---

.. index:: header_key_id/2 .. _jwt_jwa/0::header_key_id/2:

header_key_id/2 ^^^^^^^^^^^^^^^^^^^

Extracts the optional key identifier from a JWT header.

| Compilation flags: | static

| Template: | header_key_id(Header,KeyId) | Mode and number of proofs: | header_key_id(+term,-atom) - zero_or_one

---

.. index:: validate_header/1 .. _jwt_jwa/0::validate_header/1:

validate_header/1 ^^^^^^^^^^^^^^^^^^^^^

Validates a JWT header object and rejects unsupported critical header parameters.

| Compilation flags: | static

| Template: | validate_header(Header) | Mode and number of proofs: | validate_header(+term) - one_or_error

| Exceptions: | Header is not a JSON object, contains duplicate member names, or contains unsupported critical header parameters: | domain_error(jwt_header,Header)

---

.. index:: allowed_algorithm/2 .. _jwt_jwa/0::allowed_algorithm/2:

allowed_algorithm/2 ^^^^^^^^^^^^^^^^^^^^^^^

Validates that an algorithm is supported and allowed by the options.

| Compilation flags: | static

| Template: | allowed_algorithm(Algorithm,Options) | Mode and number of proofs: | allowed_algorithm(+atom,+list(compound)) - one_or_error

| Exceptions: | Algorithm is unsupported or disallowed by Options: | domain_error(jwt_algorithm,Algorithm)

---

.. index:: supported_algorithm/1 .. _jwt_jwa/0::supported_algorithm/1:

supported_algorithm/1 ^^^^^^^^^^^^^^^^^^^^^^^^^

Succeeds when the algorithm is supported by this library.

| Compilation flags: | static

| Template: | supported_algorithm(Algorithm) | Mode and number of proofs: | supported_algorithm(+atom) - zero_or_one

---

.. index:: key_type/2 .. _jwt_jwa/0::key_type/2:

key_type/2 ^^^^^^^^^^^^^^

Maps a supported algorithm to the required JWK key type.

| Compilation flags: | static

| Template: | key_type(Algorithm,KeyType) | Mode and number of proofs: | key_type(+atom,-atom) - zero_or_one

---

.. index:: hmac_hash/2 .. _jwt_jwa/0::hmac_hash/2:

hmac_hash/2 ^^^^^^^^^^^^^^^

Maps a supported HMAC algorithm to its hash object.

| Compilation flags: | static

| Template: | hmac_hash(Algorithm,Hash) | Mode and number of proofs: | hmac_hash(+atom,-object_identifier) - zero_or_one

---

Protected predicates

(no local declarations; see entity ancestors if any)

Private predicates

(no local declarations; see entity ancestors if any)

Operators

(none)