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From this answer and comments on it, a PIN is used to encrypt the phone and it must be used to decrypt it. So what happens when a PIN is changed or even removed?

  • Does changing the PIN necessarily decrypt the entire phone and encrypt again?
  • If not, does the phone need to remember every PIN ever used?
  • If a PIN is removed and the Slide to Unlock security measure is used, does the phone become decrypted? Or does it remain encrypted with the old PIN?
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  • I don't have the sources now, but the PIN is only used to encrypt the key that is actually used to encrypt and decrypt everything. So you only decrypt and then encrypt the key. The key itself doesn't change, thus you don't need to encrypt everything again.
    – GiantTree
    Jul 23, 2017 at 15:24
  • @GiantTree Do you mean this: source.android.com/security/encryption/…?
    – Firelord ♦
    Jul 23, 2017 at 15:40
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    @Firelord exactly that. I didn't feel like searching though, it's a weekend and I want to relax :)
    – GiantTree
    Jul 23, 2017 at 15:41

1 Answer 1

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A phone is encrypted with a randomly generated dedicated key, then the key is encrypted with PIN and stored somewhere else.

When you replace the PIN, it's the key that gets decrypted and encrypted again. When you remove the PIN, the key is decrypted.

It's a bad practice to encrypt the device with an easily-changeable PIN because encryption takes time, and comsumes power.

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