> This approach works by randomly polling participating devices for whether they’ve seen a particular fragment, and devices respond anonymously with a noisy signal. By noisy, we mean that devices may provide the true signal of whether a fragment was seen or a randomly selected signal for an alternative fragment or no matches at all. By calibrating how often devices send randomly selected responses, we ensure that hundreds of people using the same term are needed before the word can be discoverable. As a result, Apple only sees commonly used prompts, cannot see the signal associated with any particular device, and does not recover any unique prompts. Furthermore, the signal Apple receives from the device is not associated with an IP address or any ID that could be linked to an Apple Account. This prevents Apple from being able to associate the signal to any particular device.
The way I read this, there's no discovery mechanism here, so Apple has to guess a priori which prompts will be popular. How do they know what queries to send?
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