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Auditor app version 31 released: github.com/GrapheneOS/Aud. See the linked release notes for an overview of the improvements and a link to the full list of changes.

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Auditor pushes the limit on what can be done with a single QR code. The attestation response QR codes can be very dense. It would be significantly beyond the size of what could fit into a single QR code at all without the pre-shared dictionary DEFLATE compression we use for it.

Most QR scanning implementations can't handle dense QR codes well. The largest sizes of QR codes are usually only theoretically supported. It's really important to use a fairly high resolution overall with a real scanning zone that's cropped out before passing to the library.

Needs to be far enough away for the camera to focus on it properly while still being decent resolution. Most libraries like zxing are very bad at scanning if the QR code isn't at least 90% of the image. Combination of overly high resolution (slow) and weak support for finding it.

We use the ability to set an initial dictionary for DEFLATE to have a sample attestation certificate chain as a pre-shared dictionary. We also make sure to include both the new and old attestation root certificates so that DEFLATE can always compress them out completely from it.