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Explainer https://github.com/WICG/trust-token-api NB: We'll rename the repository to private-state-token-api when it's adopted by the antifraud CG. Specification https://wicg.github.io/trust-token-api Design docs https://docs.google.com/document/d/1TNnya6B8pyomDK2F1R9CL3dY10OAmqWlnCxsWyOBDVQ/edit Summary The Private State Token API is a new API for propagating user signals across sites, without using cross-site persistent identifiers like third party cookies for anti-fraud purposes. Anti-fraud methods that rely on third party cookies will not work once third party cookies are deprecated. The motivation of this API is to provide a means to fight fraud in a world with no third party cookies. The API prevents cross-site identification by limiting the amount of information stored in a token. Blind signatures prevent the issuer from linking a token redemption to the identity of the user in the issuance context. Private State Token API does not generate or define anti-fraud signals. This is up to the corresponding first party and the token issuers. The API enforces limits on the information transferred in these signals for privacy concerns. Private State Token API is based on the Privacy Pass protocol from the IETF working group <https://datatracker.ietf.org/wg/privacypass/about/>. It can be considered as a web-exposed form of the Privacy Pass protocols. The Private State Token API was formerly known as the Trust Token API. It is renamed to more accurately reflect its functionality. Blink component Internals>Network>TrustTokens NB: As a part of the process of renaming the Trust Token API to the Private State Token API, the blink component will also be renamed. TAG review https://github.com/w3ctag/design-reviews/issues/414 https://github.com/w3ctag/design-reviews/issues/780 TAG review status No concerns, aside from lack of clear interest from other browsers Risks Interoperability and Compatibility We intend to update the underlying cryptographic and token issuance protocols to align with the eventual Privacy Pass standard. This will affect compatibility with the small number of token issuers. Private State Token API fetch requests include a token type and version field that enables backward compatibility while allowing possible extensions for future token types and versions. While we will have a standard deprecation path of supporting multiple versions, we expect this to be easier with this API as each issuer using this API will need to register to become an issuer and will provide contact information as part of that process. Gecko: Defer <https://mozilla.github.io/standards-positions/#trust-token> WebKit: Pending (https://github.com/WebKit/standards-positions/issues/72), already shipping similar technology https://developer.apple.com/news/?id=huqjyh7k (see PST vs. PAT <https://github.com/WICG/trust-token-api/blob/main/PST_VS_PAT.md> for more information about the differences in the technologies). Web developers: Positive A limited set of developers provided feedback on Private State Tokens, indicating that the tool was valuable for anti-fraud capabilities while also acknowledging some utility challenges (1). Other developers also found that Private State Tokens provided ability for authentication purposes (as illustrated by its use in the Privacy Sandbox k-Anonymity Server) (2). 1: https://github.com/antifraudcg/meetings/blob/main/2022/yahoo-trust-token.pdf 2: https://github.com/WICG/turtledove/blob/main/FLEDGE_k_anonymity_server.md#abuse-and-invalid-traffic Other signals: Ergonomics N/A Activation Using this feature requires spinning up a (or partner with an existing) Private State Token issuer that can issue and verify trust tokens, which is non-trivial. Verifying properties of the Signed Redemption Record or the client signature requires additional cryptographic operations. It would be beneficial to have server-side libraries that developers can use to help make using this API easier. Sample code can be found at https://github.com/google/libtrusttoken. Security N/A WebView application risks Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications? As this feature does not deprecate or change behavior of existing APIs, we don't anticipate any risk to WebView-based applications. Debuggability This API is debuggable via the DevTools Application Data panel and the operations are exposed in the Network panel. Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)? Yes Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> ? Yes <https://wpt.fyi/results/trust-tokens?label=experimental&label=master&aligned>*, some of the tests are currently failing as renaming/API changes in preparation for shipping these feature haven't propagated to those tests yet. Additionally, due to the requirements of having a server-side issuer (with bespoke crypto) to fully test the API, a majority of the testing is done in wpt_internal with a bespoke python implementation of a PST issuer. Flag name TrustTokens (in the process of being renamed to PrivateStateTokens) Requires code in //chrome? False Non-OSS dependencies Does the feature depend on any code or APIs outside the Chromium open source repository and its open-source dependencies to function? Yes. Token operations are dependent on having the key commitment information configured. Chrome (and Chromium implementations that consume components from component updater) supports this via a component, other clients will need to consume the component or come up with their own method of shipping the key commitment information to the client. Estimated milestones Chrome for desktop: 113 Chrome for Android: 113 Android Webview: 113 Anticipated spec changes Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way). The major feature changes we expect are likely to be around the versions of tokens we support, as other use cases may need differing properties from those provided with the initial API and other format/API changes to align better with standardization and interop (see the Interoperability and Combatibility section up above). Most potentially web-observable changes in our open issues (https://github.com/WICG/trust-token-api/issues) are around ergonomics of using the APIs and ways to use the API in more locations/manners which should pose minimal compatibility risk to existing users of the API. Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5078049450098688 Links to previous Intent discussions Intent to prototype: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/X9sF2uLe9rA Intent to experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/UIvia1WwIhk/m/stu7iXTWBwAJ Intent to extend origin trial: https://groups.google.com/a/chromium.org/g/blink-dev/c/fpfbKgJF8Vc/m/aC8HJfGdDwAJ This intent message was generated by Chrome Platform Status <https://chromestatus.com/>. -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANduzxCC8T5D9WSrvo0yq7Tu7hdAj-YXLwuOyu2DqqkTRoHQRg%40mail.gmail.com.
