SD-JWT Reference Implementation

This is the reference implementation of the IETF SD-JWT specification written in Python.

This implementation is used to generate the examples in the IETF SD-JWT specification and it can also be used in other projects for implementing SD-JWT.

Setup

To install this implementation, make sure that python3 and pip (or pip3) are available on your system and run the following command:

# create a virtual environment to install the dependencies
python3 -m venv venv
source venv/bin/activate

# install the latest version from git
pip install git+https://github.com/openwallet-foundation-labs/sd-jwt-python.git

This will install the sdjwt python package and the sd-jwt-generate script.

If you want to access the scripts in a new shell, it is required to activate the virtual environment:

source venv/bin/activate

sd-jwt-generate

The script sd-jwt-generate is useful for generating test cases, as they might be used for doing interoperability tests with other SD-JWT implementations, and for generating examples in the SD-JWT specification and other documents.

For both use cases, the script expects a JSON file with settings (settings.yml). Examples for these files can be found in the tests/testcases and examples directories.

Furthermore, the script expects, in its working directory, one subdirectory for each test case or example. In each such directory, there must be a file specification.yml with the test case or example specifications. Examples for these files can be found in the subdirectories of the tests/testcases and examples directories, respectively.

The script outputs the following files in each test case or example directory:

• sd_jwt_issuance.txt: The issued SD-JWT. (*)
• sd_jwt_presentation.txt: The presented SD-JWT. (*)
• disclosures.md: The disclosures, formatted as markdown (only in 'example' mode).
• user_claims.json: The user claims.
• sd_jwt_payload.json: The payload of the SD-JWT.
• sd_jwt_jws_part.txt: The serialized JWS component of the SD-JWT. (*)
• kb_jwt_payload.json: The payload of the key binding JWT.
• kb_jwt_serialized.txt: The serialized key binding JWT.
• verified_contents.json: The verified contents of the SD-JWT.

(*) Note: When JWS JSON Serialization is used, the file extensions of these files are .json instead of .txt.

To run the script, enter the respective directory and execute sd-jwt-generate:

cd tests/testcases
sd-jwt-generate example

specification.yml for Test Cases and Examples

The specification.yml file contains the test case or example specifications. For examples, the file contains the 'input user data' (i.e., the payload that is turned into an SD-JWT) and the holder disclosed claims (i.e., a description of what data the holder wants to release). For test cases, an additional third property is contained, which is the expected output of the verifier.

Implementers of SD-JWT libraries are advised to run at least the following tests:

• End-to-end: The issuer creates an SD-JWT according to the input data, the holder discloses the claims according to the holder disclosed claims, and the verifier verifies the SD-JWT and outputs the expected verified contents. The test passes if the output of the verifier matches the expected verified contents.
• Issuer-direct-to-holder: The issuer creates an SD-JWT according to the input data and the whole SD-JWT is put directly into the Verifier for consumption. (Note that this is possible because an SD-JWT presentation differs only by one '~' character from the SD-JWT issued by the issuer if key binding is not enforced. This character can easily be added in the test execution.) This test simulates that a holder releases all data contained in the SD-JWT and is useful to verify that the Issuer put all data into the SD-JWT in a correct way. The test passes if the output of the verifier matches the input user claims (including all claims marked for selective disclosure).

In this library, the two tests are implemented in tests/test_e2e_testcases.py and tests/test_disclose_all_shortcut.py, respectively.

The specification.yml file has the following format for test cases (find more examples in tests/testcases):

Input data: user_claims

user_claims is a YAML dictionary with the user claims, i.e., the payload that is to be turned into an SD-JWT. Object keys and array elements (and only those!) can be marked for selective disclosure at any level in the data by applying the YAML tag "!sd" to them.

This is an example of an object where two out of three keys are marked for selective disclosure:

user_claims:
  is_over:
    "13": True          # not selectively disclosable - always visible to the verifier
    !sd "18": False     # selectively disclosable
    !sd "21": False     # selectively disclosable

The following shows an array with two elements, where both are marked for selective disclosure:

user_claims:
  nationalities:
    - !sd "DE"
    - !sd "US"

The following shows an array with two elements that are both objects, one of which is marked for selective disclosure:

user_claims:
  addresses:
    - street: "123 Main St"
      city: "Anytown"
      state: "NY"
      zip: "12345"
      type: "main_address"

    - !sd
      street: "456 Main St"
      city: "Anytown"
      state: "NY"
      zip: "12345"
      type: "secondary_address"

The following shows an object that has only one claim (sd_array) which is marked for selective disclosure. Note that within the array, there is no selective disclosure.

user_claims:
  !sd sd_array:
    - 32
    - 23

Holder Behavior: holder_disclosed_claims

holder_disclosed_claims is a YAML dictionary with the claims that the holder discloses to the verifier. The structure must follow the structure of user_claims, but elements can be omitted. The following rules apply:

• For scalar values (strings, numbers, booleans, null), the value must be True or yes if the claim is disclosed and False or no if the claim should not be disclosed.
• Arrays mirror the elements of the same array in user_claims. For each value, if it is not False or no, the value is disclosed. If an array element in user_claims is an object or array, an object or array can be provided here as well to describe which elements of that object/array should be disclosed or not, if applicable.
• For objects, list all keys that are to be disclosed, using a value that is not False or no. As above, if the value is an object or array, it is used to describe which elements of that object/array should be disclosed or not, if applicable.

Verifier Output: expect_verified_user_claims

Finally, expect_verified_user_claims describes what the verifier is expected to output after successfully consuming the presentation from the holder. In other words, after applying holder_disclosed_claims to user_claims, the result is expect_verified_user_claims.

Other Properties

When key_binding is set to true, a Key Binding JWT will be generated.

Using serialization_format, the serialization format of the SD-JWT can be specified. The default is compact, but json is also supported.