The Android Binary Transparency team at Google would like to submit our two new Tessera-backed transparency logs to the Public Witness Network for synchronous checkpoint co-signing. Below are the registration details for both logs:

1. Google Product Application Transparency Log (as detailed in https://developers.google.com/android/binary_transparency/google1p/log_details)

Origin line: android.transparency.goog/google1p/apk/2026/1

Public Key (vkey format, Ed25519 / type 0x01): android.transparency.goog/google1p/apk/2026/1+fc654374+ATr9NQE0gvOtVfj5cCStUzdlflEp3oZoNHD8pImzPj5O

Public Key (PEM Format):

Checkpoint URL: https://gstatic.com/android/binary_transparency/google1p/apk/2026/02/checkpoint

Tile Base URL: https://gstatic.com/android/binary_transparency/google1p/apk/2026/02/tile/

Log List: staging (with intent to transition to production when available)

Add-checkpoint rate: At most once every 30 seconds (~2 requests/min, < 0.1 QPS)

2. Android Mainline Modules Transparency Log (as detailed in https://developers.google.com/android/binary_transparency/mainline_modules/log_details)

Origin line: android.transparency.goog/mainline/modules/2026/1

Public Key (vkey format, Ed25519 / type 0x01): android.transparency.goog/mainline/modules/2026/1+1a8e4064+AfwnHm59rNQTJICchMd7a2W5PQa7nC5h2gTEfq3fhCEI

Public Key (PEM Format):

Checkpoint URL: https://gstatic.com/android/binary_transparency/mainline/2026/02/checkpoint

Tile Base URL: https://gstatic.com/android/binary_transparency/mainline/2026/02/tile/

Technical POC: Billy Lau (billylau@google.com)

Project documentation: https://developers.google.com/android/binary_transparency/overview

Implementation: Both logs are built on Tessera and adhere to the C2SP tlog-tiles specification (with height of 8).

Witness Interaction Policy:

- requests to witness /add-checkpoint endpoints are dispatched on a fixed 30-second interval by our backend publisher loop (internal rate-limiting prevents burst or traffic amplification).

- outbound HTTP requests are identified by User-Agent: Google-Android-Binary-Transparency/1.0 (<log_origin_string>)

- we operate in greedy collection mode with a 10second timeout, but with fail-open semantics. Temporary witness unresponsiveness or network delays will not block log ingestion or publication.

Please let me know if any additional information or adjustments are needed, and what are the next steps required.

Thank you,

Billy Lau

Android Binary Transparency Team