I don't think this is meaningfully true for modern phones. The passcode is used by the phone's TPM to derive the actual encryption key, which never leaves the TPM. TPMs are designed to be impossible to retrieve the secret key from without being physically destroyed to prevent the kind of attack you describe.

This is why phone cracking devices like Cellebrite rely on exploits in phones rather than just cloning the disk and trying the small number of possible passcodes.

Literally the point of the HSMs in phones and laptops is to stop that.

If your device's encryption key is produced by a PBKDF then yes it's doable, but no actually secure system works like that. The way a secure system works is

1. You have an HSM ("Secure Enclave" in Apple speak, Trusted Computing Module in MS speak, and I can't recall the google/android name)

2. The HSM generates a random encryption key (or family of keys)

3. The HSM encrypts and decrypts the data with those keys (the keys themselves never leaving the HSM)

4. The HSM gates access to those keys based on an attempt limited use of your passcode/password

There were common flaws a few years ago that meant that you could glitch the HSMs into (essentially) not incrementing the attempt counters or similar but I haven't heard of such in a few years now (almost a decade now? essentially these kinds of flaws were discovered en mass once HSMs reached consumer hardware so more security researchers were able to investigate)

The important thing though is the encryption key is now fully random, rather than derived from your password, which is the difference between a 128+ bit key and a ~40-60 bit key.

For dummies like myself, an HSM is a hardware security module.

Gah sorry, I was like “don’t use a useless marketing name” so instead I used a useless acronym instead, huzzah! \o/

That doesn't work with iPhones, the Secure Enclave in the only thing that can unlock the phone, and after the attempt limit is exceeded, passcode-protected data is erased by Secure Storage.

I guess if they really wanted to they could attempt to decap the chip and do something with a hardware attack, but thats difficult and dangerous.

How does gray key bypass this then? GK is still being purchased and sustainability contracts issued for LE today so I would imagine they have a way of attacking it, particularly 6 digit pins or less