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As far as I know Android (Pie) is encrypted by default with some hardware-based password. But how secure is this encryption?

I am not talking about password compromise, but if somebody gets my phone, he just needs to turn it on to get data decrypted, so what’s the point? For what cases is this encryption designed?

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  • Are you really asking "how secure is Android encryption when my phone doesn't have a password or PIN?" If that's what you're asking, then obviously it's not very secure, but that's nobody's fault but your own. Jan 11 '20 at 23:19
  • @JosephSible-ReinstateMonica maybe my wording is not the best. AFAIK encryption password is generated on hardware info only and your PIN/password is not really decrypting the info on your phone. That means, if somebody gets physical access to the phone and turns it on, data will be already decrypted. Without entering PIN/Password from your side (In case it is enabled). Correct me, if I am wrong.
    – Bukashka
    Jan 11 '20 at 23:27
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    @Bukashka have you read the answer to that question? I will quote here the relevant part: "the device encryption key is randomly generated and actually stored on the device. This encryption key is then itself encrypted using a mix of your supplied password/PIN/pattern and some device-specific hardware-backed information". Jan 11 '20 at 23:37
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    @Bukashka which basically means in order to use the device encryption key, whoever has the phone must know the device PIN/password. Have you read the official Android document regarding FDE? source.android.com/security/encryption/full-disk Jan 11 '20 at 23:39
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I am not talking about password compromise, but if somebody gets my phone, he just needs to turn it on to get data decrypted, so what’s the point? For what cases is this encryption designed?

I'm not sure from where you are quoting this statement, but it's false. Physical access to the device does not guarantee automatic decryption of the disk.

From the official Android documentation:

Upon first boot, the device creates a randomly generated 128-bit master key and then hashes it with a default password and stored salt. The default password is: "default_password" However, the resultant hash is also signed through a TEE (such as TrustZone), which uses a hash of the signature to encrypt the master key.

When the user sets the PIN/pass or password on the device, only the 128-bit key is re-encrypted and stored. (ie. user PIN/pass/pattern changes do NOT cause re-encryption of userdata.) Note that managed device may be subject to PIN, pattern, or password restrictions.

In the comments I've also referred to this question that answer a similar (if not equal) question.

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  • So, after device reboot, on lockscreen (Before PIN/Password input) user data is still encrypted?
    – Bukashka
    Jan 11 '20 at 23:55
  • @Bukashka That's correct. Jan 12 '20 at 0:04
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    But with Google you can restore access to your device (In order you forgot password), it's done by a re-encrypting the encryption key. But to re-encrypt key, it has to be decrypted. After reboot, before the first Password/PIN input encryption key is still encrypted, so Google can't restore access to your device?
    – Bukashka
    Jan 15 '20 at 19:37
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    @Bukashka that's a good question, I came here for an answer and didn't find it.
    – Aldekein
    Jan 21 '20 at 17:11
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    As the answer is on full disc encryption only but this encryption technology is no longer used on devices since about Android 9 (the version the device is released with). As far as I know Google even enforces File Based Encryption on modern devices (since Android 10?).
    – Robert
    Jan 11 at 10:40

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