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No, iOS updates require online validation because the boot rom will issue a one-time challenge based in part on the device's unique serial number, and it needs
by 0x0 10y ago
No, iOS updates require online validation because the boot rom will issue a one-time challenge based in part on the device's unique serial number, and it needs to be granted a "ticket" response by the apple servers. This is why you usually can't downgrade iOS versions (as the apple servers will refuse to grant a ticket for old versions). Google keywords: apnonce, apticket, shsh blobs, signing window
- klodolph 10y agoThis comment appears to add additional, specific information to my general comment rather than disagreeing with what I said, but the comment starts with "no", which implies otherwise. The core idea here is that SSL is not necessary if the data is signed through some other mechanism.
- mikeash 10y agoI think "no" was due to "you can distribute updates offline or from your own server and devices will still accept the updates." I assume you just meant that as a general thing, but one could read the comment as saying that because iOS signs updates this way, it can do offline updates.