What is a decoy vault?
Last updated 2026-08-05
Definition. A decoy vault is a second passcode in a vault app that opens a completely separate set of contents. Typing the real passcode opens the real vault; typing the decoy passcode opens a different one. Nothing on screen indicates which is which, or that a second vault exists at all.
It is sometimes called a duress passcode, a fake vault or plausible deniability mode. The idea comes from full-disk encryption tools, where a hidden volume can be opened with a different key.
The problem it solves
Encryption defends against someone who does not have your key. It does nothing at all against someone standing in front of you insisting that you unlock the app - a partner, a border official, a thief who saw you type the code. Cryptographers call this the rubber-hose problem: the maths is fine, the human is the weak point.
Refusing to unlock is not a neutral act. It confirms there is something to hide, which is frequently the exact thing you were trying to avoid confirming.
A decoy vault changes the shape of the situation. You unlock, fully and cooperatively. What opens is a real vault with real contents - just not the ones that matter.
What makes a decoy convincing
- Put real things in it. An empty vault is obviously a decoy. Use genuinely private but harmless contents: a few personal photos, an old ID scan, a receipt.
- Let it look used. A vault with three items added on the same day reads as staged.
- Make the app itself unremarkable. If the icon still says "Vault", the existence of the app already tells the story. Disguising the icon matters as much as the decoy contents.
- Be able to type it under pressure. A decoy passcode you have to think about is worse than none.
What a decoy vault does not do
This is where most descriptions stop, and it is the part that matters most.
- It does not defend against someone who watched you type the real passcode. They will ask for that one.
- It does not survive forensic analysis. Anyone imaging the device can see that a second encrypted store exists, even if they cannot read it. A decoy is designed for a person holding your phone, not a laboratory.
- It may not be legal cover. In some jurisdictions, failing to disclose a second vault when compelled by a court is itself an offence. A decoy vault is a defence against coercion, not against a legal order.
- It does not help if you panic. The mechanism is only as good as your composure.
Decoy vault compared with related ideas
| Mechanism | What happens | Best against |
|---|---|---|
| Decoy vault | A second passcode opens different contents | Being pressured to unlock |
| Duress wipe | A second passcode erases everything | Nothing, usually - the loss is obvious and irreversible |
| Disguised app icon | App looks like a calculator or notes app | The app being noticed at all |
| Break-in alert | Photographs whoever enters a wrong passcode | Finding out someone tried |
| Hidden album | Photo moved out of the main library view | Casual over-the-shoulder browsing |
How Vaultly implements it
In Vaultly, the decoy is a separate vault with its own encryption key, its own albums and its own contents. It is opened by entering its passcode on the same lock screen - the prompt is identical either way, and the Switch vault control in Settings is worded and shown identically whether or not a decoy exists, so its presence in the interface proves nothing.
Biometric unlock only ever opens the real vault, so Face ID cannot accidentally reveal it. The two vaults share no keys: the decoy's passcode cannot decrypt a single file from the real one.
Related reading: hidden album vs photo vault and how to hide photos on iPhone.
Questions
Is a decoy vault the same as a duress code?
They are related but different. A duress code typically triggers an action such as wiping data or sending an alert. A decoy vault simply opens different contents, which is usually safer, because a visible wipe tells the other person exactly what happened.
Can someone tell that a decoy vault exists?
Not from the interface, if the app is designed properly - the unlock prompt and settings look identical either way. Someone performing forensic analysis of the device storage can see that a second encrypted store exists, though they cannot read it.
What should I put in a decoy vault?
Genuinely private but harmless material: a few personal photos, an old document scan, a receipt. An empty or obviously staged decoy defeats the purpose, because the whole point is that it looks like the real thing.
Does a decoy vault protect me legally?
No, and it should not be relied on that way. In several jurisdictions, failing to disclose an encrypted volume when compelled by a court is a separate offence. A decoy vault is a defence against informal coercion, not against a legal order.