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Security

What DotSafe protects you from, and what it cannot

Here is who DotSafe protects you from, how it works, and what it cannot do.

DotSafe is for people who must keep photos, files and personal details private from someone who can hold their device. That person can be a partner, a family member, an employer, an official at a border, or a thief.

The most difficult case is when someone makes you open the app. Strong encryption does not help if you must unlock it yourself. For that case, DotSafe lets you open a decoy vault, and nothing shows that your other vaults exist.

Threats

Six threats, and what DotSafe does about each

Someone makes you open the app

Every pattern opens a vault, so you can open a decoy vault. There is no list of vaults. The duress pattern erases all vaults on the device.

Someone copies your device's storage

All stored data is encrypted. All blocks have the same size and random names. Cover files hide which blocks are real and how many vaults there are.

Someone tries many patterns on a copy

Each guess needs a PBKDF2 calculation with 600,000 rounds. This makes a large number of guesses slow and expensive.

A cloud service is hacked, or a court asks for your data

We have no servers and we do not store your data. With Pro, the vaults that you sync are backed up to your iCloud, but they are encrypted on your device first, so not even Apple can read them.

Someone looks at the app switcher or records the screen

DotSafe covers its window in the app switcher and hides content during screen recording. Both settings are on by default.

A password stays on the clipboard

Copies stay on this device only, and clear after 60 seconds.

Limits

What DotSafe cannot protect against

Every security design has limits. Know these before you trust DotSafe with something important.

  • A forgotten pattern. We do not store patterns or keys, so we cannot recover a vault. This is the cost of a design in which no one else can open it.
  • Someone who sees you draw the pattern. Draw it where no one can watch the screen. To make it harder to follow, turn off Show pattern trail in Settings: the grid then shows no dots or lines while you draw.
  • A compromised device. A jailbroken device, or malware that can read the memory of other apps, can see what DotSafe shows on the screen. No app can prevent this.
  • Copies that leave DotSafe. When you send a photo to another app or save it to Photos, that copy is not encrypted. DotSafe tells you this before each send.
  • A shared vault. The people in a shared vault know that it exists. A shared vault gives less deniability than a private one.
  • Two copies of your storage at different times. A person who compares them can see that data changed. DotSafe writes cover data at the same time to make this less useful, but it cannot remove it.
How the encryption works

From your pattern to the stored blocks

This is a summary. The full explanation is in How DotSafe encrypts your files.

  1. Pattern to key

    PBKDF2-HMAC-SHA256, 600,000 rounds and a random salt make a key from your pattern. Then DotSafe erases the pattern from memory.

  2. Key to vault

    The key finds and opens the index of one vault, which holds a random 256-bit vault key. If no index opens, DotSafe opens a new empty vault. It never shows an error.

  3. Vault to items

    Each item has its own random key. DotSafe splits the item into blocks of one size, fills the last block with random data, and encrypts each block with AES-256-GCM.

  4. Items to storage

    Each block gets a random name with no extension. The blocks of all vaults and the cover files are in one folder together.

What we do not have

We have no servers, no accounts and no analytics in the app. The app connects only to Apple, for iCloud and the App Store, and to this website when you open a help page. A help page that opens from the app loads no analytics. Because we receive no data, we cannot give it to anyone, and a breach of our systems cannot expose it.

Built with Apple's cryptography

DotSafe uses Apple's CryptoKit for AES-GCM, HKDF and Curve25519, and Apple's CommonCrypto for PBKDF2. It uses no third-party cryptography. All app files have iOS Data Protection at the Complete level, so iOS encrypts them again while the device is locked.

Found a security problem? Email dotsafe@mobiusly.com. Include what you found and the steps to reproduce it. We will reply, and we are happy to credit you.

Draw it. Keep it safe.

DotSafe is free for 3 vaults. No account, no email, no ads.