Pattern lock vs PIN vs passphrase: which is safer?
A passphrase of several random words is the strongest of the three. A six-digit number allows a million guesses, and a drawn pattern is easy to watch and to repeat. Anything you can only enter by looking at the screen can also be seen. For a serious threat, choose a passphrase; for casual privacy, a good pattern is reasonable.
Two ways a credential fails
A credential protects you only if it holds up against two different attacks, and they pull in opposite directions.
- Being guessed. Someone tries many possibilities until one opens the Vault. What matters is how many possibilities there are, and how much each try costs the attacker.
- Being seen. Someone watches you enter it, films it, or finds a trace of it. How many possibilities there are does not matter at all here. What matters is how easy it is to read at a glance.
Patterns are weaker on the second count than people expect. A shape drawn on a grid is one smooth movement that a bystander can follow and remember, and a camera captures it whole. A passphrase typed on the keyboard is also visible, but letters appear quickly and are harder to catch from a distance than a line sweeping across a screen. Neither is safe from a recording of your screen.
Comparing the three
| Possibilities | Easy to watch? | Cost per guess | Suited to | |
|---|---|---|---|---|
| Pattern on a 5 x 5 grid, at least six dots | Fewer than a long passphrase; we do not quote a count | Yes, one visible gesture | Slowed the same way as any credential | Everyday privacy from people nearby |
| Six-digit numeric code | 1,000,000 | Yes, six taps | Same | Not offered as a StrongRoom unlock credential |
| Passphrase of several random words | Grows with every added word | Somewhat, typed text | Same | Serious threats |
The last column hides one fact: a stretched key makes each guess slower, but it does not change how the possibilities compare. A million possibilities that take half a second each is still a small job for a determined attacker. A passphrase with many more possibilities, stretched the same way, is a much larger one.
What slows an attacker in StrongRoom
Three things sit between a guess and your Vault. None replaces a strong credential.
- Stretching. Your pattern or passphrase goes through a deliberately slow function (PBKDF2), so each guess costs real time.
- The Throttle. After ten attempts in five minutes, each further attempt waits twice as long as the last, from 30 seconds up to an hour. A separate daily allowance slows a slow trickle of attempts as well. Every attempt counts, whether or not it matched, and nothing in the delay says which.
- A secret from the Secure Enclave. The key also depends on a Device Secret that never leaves your phone. Files copied elsewhere cannot be guessed against at all, because the missing ingredient is not something an attacker can try values for.
The Throttle is enforced by the app, so it limits guessing made through the app on your phone. Copied files face a different barrier, the Device Secret. Together they bound the damage of a weak credential. They do not make a weak credential strong.
Choosing
- If the threat is a curious person nearby, such as a houseguest or a colleague, a pattern with plenty of dots and a shape that is not obvious is enough, and it is quick to enter.
- If the threat is someone who might watch you, copy your files or take time over it, use a passphrase. Pick random words, not a quote, a lyric or a phrase connected to you. Longer is stronger.
- If you might be forced to unlock, neither credential helps against being told to enter it. See the guide on what a duress password is and how a Duress Vault behaves.
Avoid anything someone could work out about you: birthdays, a pattern that is your initial, the shape of your phone passcode. StrongRoom enforces a minimum, not a good choice.
Why not Face ID
StrongRoom has no Face ID or Touch ID unlock, on purpose. A biometric would open one particular Vault, which would prove that Vault exists. A pattern or passphrase that opens nothing shows an Empty Vault, so the screen never says "wrong".
Changing and losing a credential
You can change your pattern or passphrase at any time; your files stay as they are, because the Master Key does not change. If you forget it, the Recovery Phrase on the same phone sets a new one. The optional Recovery PIN does the same job, is easier to remember and easier to guess, and never unlocks anything on the lock screen.
Keep reading
- Does a photo vault really encrypt your files?
- What is a duress password?
- Pattern and passphrase lock in StrongRoom
- Auto-lock and guess protection
- Can I use Face ID with StrongRoom?
- Limits of the Recovery PIN and of guessing protection
Frequently asked questions
Is a pattern lock safe?
It is reasonable against people nearby who do not watch closely. It is easy to see and repeat, so it is weaker than a passphrase against anyone who observes or records you.
Is a passphrase really better than a six-digit code?
Yes, if the words are random and there are several of them. A six-digit code has only a million possibilities.
Does StrongRoom offer a numeric unlock code?
No. You choose a pattern or a passphrase. The optional Recovery PIN is for recovery only and never unlocks a Vault on the lock screen.
Can I change my credential later?
Yes, any time. Your files stay as they are.
Does the Throttle make a weak credential safe?
No. It slows guessing made through the app and the Device Secret protects copied files, but a strong credential is still the first defence.