Add C2SP/Wycheproof RSA-PKCS1-v1.5 & JWS Test Vectors

[kevmoo]

Adds Project Wycheproof test vectors to validate 's pure-Dart RSA PKCS#1 v1.5 implementation.

• Adds generator tool .
• Adds and logic to parse and verify RSA signatures using exact EMSA-PKCS1-v1_5 block match.
• Exhaustive testing using Wycheproof vectors for RS256 signature verification and JSON Web Signatures.

[github-actions]

PR Health

License Headers ✔️

// Copyright 2026 Google LLC
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

Files
no missing headers

All source files should start with a license header.

This check can be disabled by tagging the PR with skip-license-check.

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
googleapis_auth	None	2.3.4	2.3.5-wip	2.3.5-wip	✔️

This check can be disabled by tagging the PR with skip-breaking-check.

Unused Dependencies ✔️

Package	Status
googleapis_auth	✔️ All dependencies utilized correctly.

For details on how to fix these, see dependency_validator.

This check can be disabled by tagging the PR with skip-unused-dependencies-check.

API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbol	Leaking sources

This check can be disabled by tagging the PR with skip-leaking-check.

Changelog Entry ✔️

Package	Changed Files

Changes to files need to be accounted for in their respective changelogs.

This check can be disabled by tagging the PR with skip-changelog-check.