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Comment on App Attest receipt update server returning 404 response
I now have more data to look at and the behaviour seems to be as follows: the receipts are issued with a not-before date of about 24 hours later and a not-after date of about 3 months later. Attempts to refresh start to fail with 404 after about 3 weeks. I now retry those failed refreshes with exponential backoff (if you don't do that, 404s quickly come to dominate). I see a very small number of receipts that refresh successfully after a period of failing. I have not yet reached the not-after date for any of these receipts; what should I do when that date arrives? Must the app generate a new key? I do have a mechanism for the server to tell the app to discard and regenerate its key, but the user does see an error message. Fundamentally, I wonder if I need to be using App Attest more frequently to keep Apple's data "fresh"; currently my attested requests are relatively infrequent.
Apr ’22
Comment on GPS speed received is 0 even though the device is moving
My code ignores the speed when it is zero. Looking at the history I added that in 2013. It may be that those are the non-GPS locations e.g. WiFi, cell towers. This is the sort of thing that can change over time with new devices and iOS changes. It can also change between you testing in one location and a user using the app in another location. Good luck with the Kalman filter idea; my experience is that the data you get from Core Location is already processed by iOS too much for you to be able to do much with it mathematically; I gave up on that sort of thing when the started snapping locations to the centrelines of streets to make them look tidier.
Apr ’22