[muyuu]

There was some comment here somewhere arguing that 16 characters for a password is too little, but that he used the pattern lock. Looks like it was deleted.

Anyway. The pattern lock in Android provides Log2(389112) =~ 18.57 bits of entropy. This is less than 3 random characters, or 4 lowercase letters, or a decimal PIN digit password of 6 characters.

Granted, you could use mnemonics for long passwords, but how convenient is to input those long passwords?

I wonder why don't they just allow for longer passwords and just use a hash digest when it's too long, rather than just disallowing people from using strong passwords that they will remember. This pushes people to reuse passwords, send them to themselves, and other bad practices.

[grapheneos]

GrapheneOS supports up to 128 character passwords to support using diceware passphrases. Using a strong passphrase avoids depending on the secure element. A random 6 digit PIN is secure due to the secure element rate limiting. Only a total of 20 attempts are permitted so even a random 4 digit PIN would be fine.

GrapheneOS adds the option to set a 2nd factor PIN for fingerprint unlock to make using a strong passphrase convenient without the downsides of biometric-only unlock.

Pattern lock strongly encouraging using only a tiny subset of the possibilities so it's much worse than your analysis shows. It was removed from GrapheneOS years ago because it's far worse than simply generating and using a random 6 digit PIN despite appearing to be similar. It gives a false sense of security and we didn't want to add support for a duress pattern or random pattern generating alongside those planned features. Built-in random PIN and passphrase generation is still in progress but has been started and will be shipped.

[frumiousirc]

Perhaps bad/naive ideas, but consider these options for unlocking where the requirements changes after one incorrect entry.

- After an incorrect key, require two (or more) consecutive valid key entries.

- After an incorrect key, no longer accept that nominal key until a secondary key is supplied.

[inigyou]

Thank you for your service.

[muyuu]

yep, human bias makes 4-digit pins and patterns a lot worse than the theoretical entropy, but still it's a decent starting point

my comment was about the decision of that person who deleted the comment to go for the pattern lock, while/because? 16 chars was supposedly bad for the password (although he/she has a point in that the limitation is annoying and counterproductive)

all of this i reckon was not criticism of GrapheneOS but stock Android, AFAIK grapheneOS's choices are all very sound

[Cider9986]

>>To make a strong passphrase convenient to use without ruining it with biometric unlock, GrapheneOS adds an optional 2nd factor fingerprint PIN. We reduce the allowed fingerprint attempts from 20 to 5 and failure to enter the correct 2nd factor PIN counts towards it. This enables using 6-8 random diceware words as the main unlock method required in Before First Unlock and fingerprint+PIN using a short PIN for convenience. Using a valid fingerprint prompts to enter the 2nd factor PIN which is needed to complete unlocking the screen and hardware keystore.

Pattern lock isn't exposed to the user afaik because it's insecure.

>I wonder why don't they just allow for longer passwords

They allow up to 128 digit passwords which they changed from AOSP.

I use a long passphrase for primary unlock and it's convenient because you only enter it when you restart.

If you rely on the secure element than 6 digits is fine. A long passphrase ensures you're protected even if the secure element is exploited.

[jeroenhd]

Modern Pixel phones have a TPM-like device that protects against brute-force attacks. Assuming the pattern is non-obvious, an attacker has 20 attempts before the supplementary key material is wiped and the encryption key is lost.

It's theorerically possible to use side channel attacks against the security chip to bypass this, of course, but that requires opening the device and some very precise, damaging operations, assuming the attacker has a known-working side channel attack in the first place.

[brendyn]

Maybe because it was mistaken. I just set my grapheneos to a 35 character password to test it and it didnt seem to have any issue.

[b112]

Did ypu test using random characters after 30 chars?

[muyuu]

nope it was arguing that this is a difference with stock android and that it is 16 chars there, idk about that though