6 ms·

How is a 6 digit pass code too few possibilities when the phone locks you out after like 5 missed attempts? It seems unrealistic to expect people to type their

How is a 6 digit pass code too few possibilities when the phone locks you out after like 5 missed attempts? It seems unrealistic to expect people to type their alphanumeric password every time they want to unlock their phone.

nijave 3y ago
If these are implemented in software it'd be possible to brute force offline and bypass the timeout
- Gigachad 3y ago
  I watched a video where they had the iphone cracked open and slightly modified in a way that would allow them to reset the storage to brute force quickly without timeouts.
  - lxgr 3y ago
    That shouldn’t be (at least easily) possible on newer iPhones anymore. The counters are now in rollback-protected dedicated memory; the lockout is implemented in the secure enclave.
    - Gigachad 3y ago
      Sure, but this is all protected by dubious hardware that often gets cracked. A text password is protected by pretty sound math.
haswell 3y ago
If I recall correctly, some early techniques to unlock passcode-protected phones involved bypassing the user interface and trying passcodes at a point in the execution flow prior to the code that locks out the UI. I think modern devices have addressed this in various ways, but it’s not a good idea to rely on timed lockouts when it’s possible that techniques exist (or could eventually be found) to bypass the lockout. In short, assume those lockouts are targeted at normal users. A sufficiently motivated actor with technical resources is another story.
- deleted 3y ago
  [deleted]
HenryBemis 3y ago
I am thinking that a numeric code is something that people can see you typing in again and again. An ex-bf/gf that hates your guts will remember that your pin is 1-2-3-4-5-6, because that one time your hands were wet and she needed to see that photo from that party and you told her the PIN.. While if you have a word, new bf/gf will mean new word, and good luck knowing that.
- pseudalopex 3y ago
  A numeric code may be easier to shoulder surf. Nothing prevents you from changing a numeric code or ensures you will change an alphanumeric code however.
  - calvinmorrison 3y ago
    Glad runescape solved this in 2004 by implemented randomized positions for each digit
    - HideousKojima 3y ago
      Heck, the keypad at my church in my hometown did this back in the mid to late 90's (if not sooner)
ncallaway 3y ago
The government will clone your device hard-drive, then be able to attempt to unlock it on many simulated devices in parallel, until one unlocks. Then they can unlock the actual device.
- dathery 3y ago
  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.
- amlozano 3y ago
  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.
  - chislobog 3y ago
    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
- olliej 3y ago
  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.
ddingus 3y ago
In some cases, they can attack the password outside the phone / device environment by comparing hashes. At the very least, such an effort may well be able to reduce the problem space considerably, leaving it down to a few guesses on the device.
Quillbert182 3y ago
I can’t seem to find it now, but I remember a news story a while back where a police agency was able to unlock an iPhone with a 6 digit numeric passcode in a little over a year, bypassing the hardware security module and time limits.

nijave 3y ago

If these are implemented in software it'd be possible to brute force offline and bypass the timeout

Gigachad 3y ago
I watched a video where they had the iphone cracked open and slightly modified in a way that would allow them to reset the storage to brute force quickly without timeouts.
- lxgr 3y ago
  That shouldn’t be (at least easily) possible on newer iPhones anymore. The counters are now in rollback-protected dedicated memory; the lockout is implemented in the secure enclave.
  - Gigachad 3y ago
    Sure, but this is all protected by dubious hardware that often gets cracked. A text password is protected by pretty sound math.

haswell 3y ago

If I recall correctly, some early techniques to unlock passcode-protected phones involved bypassing the user interface and trying passcodes at a point in the execution flow prior to the code that locks out the UI. I think modern devices have addressed this in various ways, but it’s not a good idea to rely on timed lockouts when it’s possible that techniques exist (or could eventually be found) to bypass the lockout. In short, assume those lockouts are targeted at normal users. A sufficiently motivated actor with technical resources is another story.

deleted 3y ago
[deleted]

HenryBemis 3y ago

I am thinking that a numeric code is something that people can see you typing in again and again. An ex-bf/gf that hates your guts will remember that your pin is 1-2-3-4-5-6, because that one time your hands were wet and she needed to see that photo from that party and you told her the PIN.. While if you have a word, new bf/gf will mean new word, and good luck knowing that.

pseudalopex 3y ago
A numeric code may be easier to shoulder surf. Nothing prevents you from changing a numeric code or ensures you will change an alphanumeric code however.
- calvinmorrison 3y ago
  Glad runescape solved this in 2004 by implemented randomized positions for each digit
  - HideousKojima 3y ago
    Heck, the keypad at my church in my hometown did this back in the mid to late 90's (if not sooner)

ncallaway 3y ago

The government will clone your device hard-drive, then be able to attempt to unlock it on many simulated devices in parallel, until one unlocks. Then they can unlock the actual device.

dathery 3y ago
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.
amlozano 3y ago
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.
- chislobog 3y ago
  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
olliej 3y ago
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.

ddingus 3y ago

In some cases, they can attack the password outside the phone / device environment by comparing hashes. At the very least, such an effort may well be able to reduce the problem space considerably, leaving it down to a few guesses on the device.

Quillbert182 3y ago

I can’t seem to find it now, but I remember a news story a while back where a police agency was able to unlock an iPhone with a 6 digit numeric passcode in a little over a year, bypassing the hardware security module and time limits.