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Modern Android devices have encryption for the storage. It is secured with a key which is derived from the lock screen and a hardware bound key.

We know that the rate limiting mechanism prevents brute forcing the PIN on the device, but what actually prevents a thief, after stealing the phone, from disassembling the hardware and extract the key material, and also the storage in it, while brute forcing the pattern or PIN offline by connecting the storage onto a computer?

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  • "extract the key material" -- how do you image that happens?
    – schroeder
    Mar 16 at 10:10
  • "why can't you just brute-force the encryption?" -- you can. Do you have until the heat death of the universe to wait until that happens? Nothing says that encryption can't be brute-forced. Encryption makes it infeasible to bruteforce securely encrypted material. If it takes more than 50 years to break, does it matter that you can break it?
    – schroeder
    Mar 16 at 10:11
  • It's trivial to brute force the PIN or pattern if the device is taken offline. What makes it supposedly secure is that, the PIN is combined with a device-specific hardware bound key which is embedded in the hardware and infeasible to brute force to produce the encryption key. However, if the thief has physical control of the device, isn't it trivial to disassemble it and extract the key out of the hardware? Mar 17 at 11:41
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    Does this answer your question? Connection between PIN/password and encryption keys in Android
    – defalt
    Mar 18 at 19:27
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    TEE with RPMB partition as storage & SE's secure storage are designed to be resistant against physical attacks. It is infeasible to extract keying material from them. Their physical security is based on hardware obfuscation. The linked question answers your question in your title.
    – defalt
    Mar 20 at 13:39

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