Locked before it leaves your device

Our server syncs your data between your devices but has no way to open it. A shared project opens only for the people you invite.

What stays private

Everything you write is encrypted on your device before it syncs. Only the current version of each item is kept, never a history of your edits.

Encrypted on your device

  • Titles and notesEverything you write
  • Dates, times and remindersYour schedule and what is due when
  • Labels, priority and assigneesHow you sort your tasks and who is on them
  • AttachmentsThe files and their names
  • Project, section and label namesHow you organize
  • Repeats and habit historyHow often things repeat and every completion you log
  • Your settingsDown to which projects you hide

What our server can see

  • About your itemsRandom IDs, which project each item is in, and when it was created, changed or deleted. For attachments, roughly how big each file is.
  • About your accountThe username you pick (no email or phone number), your Pro status and how you paid, and whether you use two-factor authentication, passkeys or a decoy PIN. If you use an authenticator app, the key that lets us verify its codes.
  • About shared projectsWho the members are and their roles.

Items marked as deleted stay encrypted for 30 days so your other devices can catch up. Then they are deleted.

One task as we store it.

id
3f8a2c71-9d0e-4b5a-a1c6-52e0d7b4c1f8
owner
c04e9b2a-5f17-4d83-9e61-7ab2f0d4c935
project
91be0d4e-77a2-4f19-b0c3-0a6d2e8f4b17
created
2026-10-14 09:12
changed
2026-10-16 18:40
deleted
–
key
Xp4mQ9vL2cR7tB0wK5nJ8yF3hD6sA1gZ=
content
kQ7vR2xZ0bWmP4tN8sLc1yHq3eJfU6gA9dKoV5iT2rXnB7wE0zMuY4pS8hGjC1lF6aDqO3vI9kR5tWbN2xZp2Lw9=

App lock

Lock the app with a PIN, your fingerprint or your face. Until you unlock it, your data stays locked too.

  • PIN. At least 6 digits.
  • Fingerprint or face. Uses your device's own unlock with your PIN behind it.
  • Wrong guesses. From the third wrong try you wait longer each time: 30 seconds, then a minute, then two. Restarting the app does not reset it.
The unlock method dialog, offering no lock, a PIN code of at least 6 digits, or biometrics, and when to ask for it.

Decoy PIN

For when someone can make you unlock your phone. Enter the decoy PIN and the app opens a second profile with only the projects you marked as decoy. Nothing in it shows that more exists.

  • Decoy profile. You choose which projects it shows. It has its own Inbox and works like the real app.
  • Panic PIN. Optional. Opens the decoy profile and first deletes your real data from this device. With an account your encrypted copy comes back when you sign in on another device.
  • Free. Set it up once you have a PIN or fingerprint unlock.
The decoy PIN settings with each project marked real or decoy and a button to move it to the other profile.

Two-factor authentication

Sign in with two of these: your password, a passkey or a code from an authenticator app. Free on every plan.

Your authenticator's key is stored encrypted and used only to verify your codes. It protects signing in only: it cannot open your data.

If you forget your password

Lockday asks for no email or phone number so there is no password reset. A passkey still signs you in without your password. Without one, nobody else can unlock your data for you.

  1. Save your decryption secretThe app offers a 24-word phrase or a password of your own. Keep it somewhere safe.
  2. Back up to a fileA backup is one encrypted file with your data. It opens on any device with your secret.
  3. Add a passkeyOn Android, iPhone and the web, a passkey signs you in without your password.

The cryptography

Content encryption AES-256-GCM

Envelope encryption: every task, label, file and template is sealed with its own data key.

Key derivation Argon2id

Memory-hard (m=64 MiB, t=3) so guessing your password stays slow and expensive even on GPUs and ASICs. Runs only on your device.

Key wrapping X25519 + ML-KEM-768

A post-quantum hybrid (ML-KEM-768, NIST FIPS 203, combined with X25519). Each project key stays sealed as long as either algorithm holds so your data survives a future quantum computer.

Password storage (server) BCrypt

Over a hash that was already computed on your device.

Transport TLS + signed JWT

Encrypted in flight with signed access tokens.