Hi all,
We wanted to provide an update after reviewing Mozilla’s feedback and a few rounds of good discussion in the threads. We are making several small but significant changes based on the suggestions, after which we’d like to launch Private State Tokens in order to support some anti-fraud use cases that are currently using 3rd party cookies, so developers don't turn to fingerprinting as a replacement. This will also let us benefit from additional feedback in the wild before making final decisions on some of the other suggested changes. We believe we'll be able to migrate the ecosystem to whichever option we settle on in the final standard (issue #235 <https://github.com/WICG/trust-token-api/issues/235> explains our rationale and approach for how we’re triaging the feedback and managing potential migrations). We have several specification improvements in flight, which will hopefully address all of the spec concerns raised, and we plan to make the following code changes: - Removal Private Metadata Bit from web API (we still intend to keep the Chromium implementation around to support non-web-visible features; but it will no longer be available via the Private State Token API) until the crypto can be standardized. - Update to the current VOPRF version. - Add permissions policy for token issuance to match the existing policy for token redemption. - Remove 'type' from the API. We are targeting these changes to land in M114. Thanks, Eric & PST team On Wed, Apr 12, 2023 at 2:53 PM Mike Taylor <miketa...@chromium.org> wrote: > Whoops, that happened in > https://github.com/w3ctag/design-reviews/issues/780#issuecomment-1422995031 > - please ignore. :) > On 4/12/23 2:37 PM, Mike Taylor wrote: > > One other comment, in > https://github.com/w3ctag/design-reviews/issues/414#issuecomment-975743619 > - the TAG requested that y'all ping the thread when the spec was more > concrete (or open a new issue). Probably a good time to do so now. > On 4/6/23 11:18 AM, Mike Taylor wrote: > > Thanks for the response, appreciated. > On 4/6/23 10:02 AM, Steven Valdez wrote: > > Re: Supporting multiple crypto versions, there's no real utility beyond > compatibility because particular UAs will only select one of the versions > (based on their preferences), rather than trying to negotiate the crypto > version. > > There's some discussion on standardizing to a RFC version of privacypass, > however for the actual API surface, the PAT API is primarily triggered via > HTTP-Authentication and they haven't seen a strong need for a JS API to > trigger issuance, while for PST we see the other direction where the JS API > is the primary way of triggering it (since its harder for origins to make > server-side changes to their header/challenge via HTTP auth compared to > adding new JS API calls). > > On Wed, Apr 5, 2023 at 6:33 PM Mike Taylor <miketa...@chromium.org> wrote: > >> Thanks for linking to >> https://github.com/WICG/trust-token-api/blob/main/PST_VS_PAT.md - it's a >> really useful doc that I missed on my first read of this Intent. >> >> The API OWNERs (Yoav, Alex, Daniel, Philip, myself) were discussing this >> intent today and had some questions that are partially answered by the >> PST_VS_PAT doc. Another question - have there been any discussions with >> Apple on a possible convergence of these APIs? The doc hints at a future >> unification to create a shared API surface for token issuance/redemption. >> On 4/5/23 10:03 AM, 'Steven Valdez' via blink-dev wrote: >> >> Private Access Tokens is roughly based on the Rate Limited privacy pass >> specification ( >> https://github.com/ietf-wg-privacypass/draft-ietf-privacypass-rate-limit-tokens/ >> ). >> >> It is primarily triggered via HTTP-Authentication headers and doesn't >> have a way of exposing that via a JS API. Developers are expected to have >> endpoints that provide HTTP-Authentication challenges that trigger the OS >> to issue/redeem tokens. >> >> There's a bit of a discussion of the similarities/differences between the >> APIs at https://github.com/WICG/trust-token-api/blob/main/PST_VS_PAT.md. >> >> There's some overlap between the use cases, but for the CAPTCHA use case, >> while the platform-level signal is useful, anti-fraud providers tend to >> want to use additional signals to feed into their decision whether to >> present something like a CAPTCHA, and being able to store the result of >> their distillation of the decision in tokens they issue can be useful. >> >> On Wed, Apr 5, 2023 at 3:53 AM Yoav Weiss <yoavwe...@chromium.org> wrote: >> >>> >>> >>> On Fri, Mar 17, 2023 at 5:35 PM Steven Valdez <sval...@chromium.org> >>> wrote: >>> >>>> Contact emails >>>> >>>> ayk...@google.com, sval...@chromium.org, kaustub...@chromium.org >>>> >>>> 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). >>>> >>> >>> Not on you, but do Private-Access-Tokens have something resembling a >>> specification or an explainer, other than marketing material? >>> Do I understand correctly that they are strictly based on protocol-level >>> negotiation, without a JS API? How are developers supposed to interact with >>> them? >>> >>> Is there overlap between the use-cases? (e.g. I would naively think that >>> CAPTCHA avoidance can rely on either/both OS-level and anti-fraud provider >>> attestation) >>> >>> >>>> >>>> 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 blink-dev+unsubscr...@chromium.org. >>>> To view this discussion on the web visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANduzxCC8T5D9WSrvo0yq7Tu7hdAj-YXLwuOyu2DqqkTRoHQRg%40mail.gmail.com >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANduzxCC8T5D9WSrvo0yq7Tu7hdAj-YXLwuOyu2DqqkTRoHQRg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >>> 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 blink-dev+unsubscr...@chromium.org. >>> To view this discussion on the web visit >>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfUOedJX%2BHs1kHDRGByLPaTV23nDHUCxzbRqDz81hbO0Jw%40mail.gmail.com >>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfUOedJX%2BHs1kHDRGByLPaTV23nDHUCxzbRqDz81hbO0Jw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> >> >> -- >> >> Steven Valdez | Chrome Privacy Sandbox | sval...@google.com | Cambridge, >> MA >> -- >> 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 blink-dev+unsubscr...@chromium.org. >> To view this discussion on the web visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANduzxBRmxhQ4e_LTK_fDG7e9VKyNCe1EUOmmkkUXmDc02Md_A%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANduzxBRmxhQ4e_LTK_fDG7e9VKyNCe1EUOmmkkUXmDc02Md_A%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> >> > > -- > > Steven Valdez | Chrome Privacy Sandbox | sval...@google.com | Cambridge, > MA > > -- > 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 blink-dev+unsubscr...@chromium.org. > To view this discussion on the web visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/0c07740f-e250-772d-5c4b-a2726dc86e81%40chromium.org > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/0c07740f-e250-772d-5c4b-a2726dc86e81%40chromium.org?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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