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Background

I am trying to unlock my Google Pixel 6. Due to an accident, I lost much of my memory and in turn, forgot the lock screen PIN code for my phone. I have, however, also activated fingerprint detection for unlocking my phone.

Now, the issue is that the device ran out of battery while I was in a coma, and upon trying to use my fingerprint to unlock the device, I received the following message:

lock screen message

PIN required after device restarts

I have tried remembering the PIN for the past few months, however, I frankly cannot remember. As I have important data stored on the device locally (that is not backed up as far as I can recall), a factory reset is not really an option for me.

Question

Is there any way of enabling the fingerprint sensor on a Pixel 6 to unlock the phone (via adb or similar) or any other means of unlocking the device without wiping all data?

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  • On my android, it immediately unlocks on the correct code being keyed in. In theory you could try bruteforcing it - there's apparently a few software tools that work over USB OTG emulating a keyboard that do this. I'd start with numbers meaningful to me though, birthdays and so on. Its a terrible way, but it might work Sep 17, 2023 at 2:15
  • Too late for your situation unless this is something you did but forgot: some password managers permit to set up recovery contacts that can unlock your stored passwords/PINs after a certain delay, which is what I set up bitwarden to use. It's a paid feature but definitely worth the few bucks Sep 18, 2023 at 9:01
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    My Pixel 6 gets backed up to Google servers every night. Are you sure you didn't have this set up? Sep 19, 2023 at 1:51
  • @OrganicMarble I am not certain which account I used on my phone. Do you happen to know if there is any way of looking up stored backups from e.g. a laptop? Sep 20, 2023 at 11:53

3 Answers 3

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Unfortunately there is no way to use fingerprint as authentication directly after rebooting the device.

The first unlock always have to be performed using the PIN/password, because the PIN/Password is passed on into the Gatekeeper system (the central Android security core) and there combined with other keys to generate the master encryption key.

That means without the correct PIN/password the gatekeeper can not build the key that is necessary to decrypt your user data.

Biometric authentication systems can not be used to generate something reproducible so you can not derive an encryption key from it. This is the reason why Google had to implement it that way. And to answer your question, even if there would be a way to enable fingerprint authentication directly after boot it wouldn't help you as the user data would remain locked. As without the correct PIN/password the decryption key can not be generated.

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Robert's answer describes why you unfortunately cannot unlock an android phone with a fingerprint after a reboot. However, depending on you password habits, there's a significant chance you can guess your pin with surprisingly few attempts.

For example, cybersecurity professional Tarah Wheeler claims the following 20 pins are most common and will unlock 26% of all pin locked phones:

1234, 1111, 0000, 1212, 7777, 1004, 2000, 4444, 2222, 6969, 9999, 3333, 5555, 6666, 1122, 1313, 8888, 4321, 2001, 1010

(other readers, if you use one of these pins, it is a good idea change your pin)

If none of these pins work, you can find similar lists by performing a web search along the lines of "most common phone pins". Other common pins that won't nessesarily appear in such lists include the user's birth month and day, user's birth year, birth days and months or birth years of the users loved ones, the user's year of graduation, or other dates of significance to the user.

If the most common pins don't work, you can use a tool like Android PIN Bruteforce (software) or a USB Rubber Ducky (hardware). These tools can pretend to be a keyboard and type in pins automatically, waiting a little between attempts. Reportedly, all 4 digit pins can be tried in just under 17 hours without triggering a lockout (neat but scary).

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    Before brute forcing make sure you didn't set up any "wipe on x failed attempts" feature - though IIRC natively Android doesn't have such a feature thus making this unlikely Sep 18, 2023 at 8:59
  • This is why security conscious users should probably set up an 8 digit pin. There are many tricks how you can easily remember an 8-digit pin (combine a birthday with some other pin you use, interleave a birthday with a single number, or 1,2,3,4, ...) this will most likely prevent any brute-forcing without serious social engineering.
    – Falco
    Sep 18, 2023 at 10:20
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Vaelus' answer is the most useful one here, and did well to cover the actual kinds of tools you want to be looking into, so I won't repeat those here - this answer is more concerning the methodology of what you need to do, as well as a little motivation.

It's no longer possible to unlock your phone through legitimate means (and if it was, no Android phone could ever be considered secure). Your only chance of getting into your phone now is to think like a hacker, where the target is yourself. The good news is that - as any hacker will tell you - the more information you have about a target, the better your chances, and no-one has more information about yourself than you do. Even if your memory is no longer reliable at all, that information is likely still easily accessible to you, either noted down or in the memories of those around you - your secure pin codes, the birthdates/years of significant people in your life, the date you got married, and so on. In other words, no-one is better placed to hack into this phone than you are.

Bear in mind that all the numbers you're looking for will be the same length as your passcode, which you can get by entering a wrong code and seeing how many digits you can enter before it automatically fails.

Once you've compiled a list of your significant numbers, combine it with the list of common pincodes in Vaelus' answer and any other similar lists you can find, then run your list as a dictionary through one of the Android brute-forcing tools. You could also just try each code one by one, since you also have another luxury that most hackers don't - unlimited access time with the physical device - and therefore never need to worry about being permanently locked out; at any time you can just stop and try again tomorrow.

If you're unsuccessful even after several more months, your best bet at that point would probably be to hire the services of a reputable white hat hacker with experience in this field. Whether that's worth it for you depends on how much that service would cost, and whether that cost is worth the value of the data you have on the phone.

All the best for your (health and data) recovery, and good luck.

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    If you can find your pin-codes for other services, try them - many people reuse codes (a single pin for bank-account, smartphone, laptop)
    – Falco
    Sep 18, 2023 at 10:22

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