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This especially affects used phones. How does a non-technical buyer know whether it is pre-rooted/jailbroken or not?

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Jan 24, 2019

The 'returned product attack' here - buy, replace the firmware, return and hope someone else buys it - is a real-world evil maid attack, and speaks very much to why we need secure boot on IoT systems. Supply chain security is more complex that 'just' up to FOB delivery. twitter.com/CANcrypt/statu…

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Thought about doing this as a research project many many years ago, but decided it didn't have research value and would likely be a lot of trouble to actually do. This was after buying heaps of used Android phones on eBay and finding all kinds of things on them.

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attestation.app/about is able to check for that kind of tampering. If it's a sophisticated attack, they could have a verified boot bypass via an exploit triggered during the verification process on boot, but attestation can detect the device isn't updated if it's only OS level.

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Nice new domain for this (or at least, new to me)! Would be great to see some iOS support for this kind of thing also.

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The ideal case would be for sending a phone through the mail, where the person sending it sets up pairing with the person receiving it before sending it. That gives it the full strength it's meant to have and something similar could be done for iOS with hardware-backed keys.

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I don't think iOS has something like key attestation or a way to do remote attestation though. It's just not one of the APIs that's available, so an equivalent to the app can't really be made for it. The Android APIs for it aren't perfect but they're useful and getting better.

2:34 PM · Jan 24, 2019Twitter Web Client

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I bet they do just not exposed to the developer/user.

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Apple has some useful primitives like key generation inside secure enclave, but there is no key attestation. DeviceCheck is a new API to verify validity of an iOS device, but it doesn't cover device integrity.

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One thing it's missing is more information about the firmware rather than only the focus on the OS. It would be nice to receive versions of various firmware components in the signed output too, but it'd need some way of including hardware-specific extended versions for that.