NullKey NullKey vs disguised vault apps
NullKey is an Android app that keeps private notes, documents and photos in an encrypted vault on the phone, with no sync and no disguise. Disguised vault apps put the vault behind another app's icon or opening screen. This page compares what you get from each approach, and it describes the type of app in general, not any one product.
The description of disguised vault apps is general, because features vary between apps. NullKey facts come from the app itself and the sources below, and were last reviewed on 10 November 2026. Spot something out of date? Email hello@alvento.uk.
Feature comparison
Scroll the table horizontally to see both options.
| Point | NullKey | disguised vault apps |
|---|---|---|
| Can disguise the app or show a decoy | No. | Yes, by definition. The app is disguised, for example by its icon or opening screen, and some show harmless decoy content when a second code is entered. |
| Encrypts the stored files on the device | Yes. Contents use AES-256-GCM with a separate random key for each item. Argon2id turns your passphrase into a key that protects the vault master key. | Varies by app. A disguise is a separate feature from encryption, so check the app's own description for how files are protected. |
| Offers cloud backup or sync | No app-run sync or cloud backup. The current app declares no internet permission. You choose an available destination for an encrypted backup with Android's document picker. | Varies by app. Some keep files only on the phone and some offer an online backup. |
| Has a way back in if you forget the unlock secret | A recovery key that you save yourself. There is no account reset. | Varies by app. Check how an app handles a forgotten code. |
| Needs an account or sign-in to use | No. There is no account. | Varies by app. Some ask for an email address or an account. |
| Stores notes and documents, not only photos and videos | Yes. Private notes, documents and photos. | Varies by app. Some focus mainly on photos and videos. |
| Shows ads | No ads. | Varies by app. Some are free to get and show ads. |
| Has in-app purchases or a paid tier | One optional one-time unlock. No subscription. | Varies by app. Some have a free tier and a paid tier. |
The honest case for disguised vault apps
A disguised vault app may suit a reader whose main worry is someone glancing at the phone and noticing a vault app. The disguise is the point of the category: the icon or opening screen looks like something unremarkable, and getting into the vault takes a particular step. NullKey does not do this. It appears under its own name and icon.
Some apps in this category also show harmless decoy content when a second code is entered. That suits a reader who wants a second code that opens something ordinary. NullKey has no decoy code, so it cannot offer that.
Hiding the app or protecting what is inside
A disguise may make a vault app less obvious. Encryption protects the contents if someone finds the app anyway. The two are separate features, and an app can have one without the other, so the app's own description is where to look for how files are protected.
NullKey does not disguise itself. It encrypts each item with AES-256-GCM using a separate random key, and Argon2id turns your passphrase into a key that protects the vault master key.
Recovery and accounts
Recovery options differ between disguised vault apps. A reset that goes through an email address held by the developer is convenient, and it means giving the developer an address and trusting the reset process.
NullKey has no account and no reset by email. Its way back in is a recovery key that you save yourself, so nobody at Alvento can open the vault for you.
Backups, ads and purchases
Backup arrangements and money models vary widely in this category. Some apps are free to get and show ads, and some offer a paid tier. Some keep files only on the phone and some offer an online backup.
NullKey shows no ads and has no sync. It is free for up to 30 items, with one optional one-time unlock and no subscription. You choose an available destination for an encrypted backup with Android's document picker.
Bottom line
Choose a disguised vault app if hiding the app itself matters most to you, and read its own description for how it protects files and handles recovery. Choose NullKey if you are on Android 12L or later and want encrypted notes, documents and photos with no account, no ads and a recovery key you keep yourself, accepting that the app is not disguised.
References
- https://alvento.uk/nullkey/security/ (fetched 10 November 2026)
- https://play.google.com/store/apps/details?id=uk.alvento.nullkeyapp&hl=en_GB (fetched 10 November 2026)
Frequently asked questions
Does NullKey hide its icon or show a decoy?
No. NullKey has no disguise or decoy mode. It appears under its own name and icon.
Do disguised vault apps encrypt the files they hold?
It varies by app. A disguised icon is a different feature from encryption, so check the description of any app you consider. NullKey encrypts each item with AES-256-GCM and protects the vault key with a key derived from your passphrase using Argon2id.
Does NullKey need an account or show ads?
No account and no ads. There is one optional one-time unlock, with no subscription.
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