Encrypted Notepad

About the Encrypted Notepad

An ordinary notepad leaves your notes readable to anyone who opens the browser or the device. This one encrypts every note before it is saved: the text is sealed with AES-256-GCM under a key made from your password with Argon2id, a deliberately slow, memory-hungry function, and only the scrambled result is kept in this browser (IndexedDB). The password and the key never leave the tab, nothing is uploaded, and the notebook works offline.

The notebook locks itself after a time you choose, on a click, or when you leave the tab, and it removes the notes and the key from the page. Because the notebook is never sent to a server or kept with an account, there is also no reset: a forgotten password cannot be recovered by anyone, and clearing the browser’s site data deletes the notes. So the page makes an encrypted backup file easy to save and restore — on this device or another — and says plainly what is at stake before you start.

Without a pass the notebook works in full on your device. What the free preview holds back is the encrypted backup file: saving it unlocks with a Pro pass, or by unlocking that backup. Copying or downloading a note as plain text, and restoring a backup, are always open.

Common uses

• Keeping recovery codes, account numbers, PINs and Wi-Fi keys out of an ordinary, readable notepad.
• A private journal or work notes on a computer or phone that other people use.
• Drafts of sensitive letters, reports or messages, before they go anywhere else.
• A staging place for secrets on their way into a password manager.

How your notes are protected

1. Your password is normalised (Unicode NFC) and stretched with Argon2id (RFC 9106) and a random 16-byte salt into a 256-bit key. The default setting is RFC 9106’s second recommended option — 64 MiB of memory, 3 passes, 4 lanes — so every guess against a stolen copy costs memory as well as time. Light is OWASP’s minimum (19 MiB, 2 passes), Strong uses 256 MiB.
2. Each note is sealed with AES-256-GCM (NIST SP 800-38D) under a fresh random 96-bit IV. The note’s id is bound in as authenticated data, so a ciphertext cannot be moved to another note unnoticed, and any changed bit makes opening fail.
3. A small check record, a sealed constant, tells a wrong password from a right one: it only opens under the right key.
4. The key is a non-extractable Web Crypto key held in memory while the notebook is open, and dropped when it locks.

What is stored, and what is not

The database tv-encrypted-notepad holds the notebook’s record (the key settings, the salt and the check record) and, for each note, an id, an IV and the ciphertext. The password, the key and the text are never stored, and neither are titles or dates: they are inside the ciphertext.

What someone with access to the browser’s storage can still see is that the notebook exists, how many notes it holds and their sizes, rounded to 256 bytes. They can delete notes, or put back an older copy of one; they cannot read or change one without the password.

Choosing a password

Anyone who copies the stored notes can try passwords offline as fast as their hardware allows, and nothing can slow them down except the Argon2id setting. The password is therefore the real protection. NIST SP 800-63B asks for at least 15 characters when a password is the only factor protecting something, as it is here, and says not to impose rules about mixing character types: length wins. Four or more random words, or a password manager’s 16 or more random characters, hold up far better than anything you could remember by pattern. The page refuses anything under 12 characters and suggests 15 or more.

Auto-lock

The notebook locks after 1, 5, 15, 30 or 60 minutes without use, never (only when you press Lock), and optionally the moment you switch to another tab or app. Locking first saves the note you are typing, then removes every note, the key and the search from the page. It cannot erase what the browser, the operating system or a screenshot may already have copied, so lock early on a shared device, and use a screen lock too.

Backups, a new password and other tabs

• Backup: one JSON file with the key settings, the salt and the sealed notes. It needs the password it was made with, which is the password at the time.
• Restore: on a device with no notebook the backup becomes the notebook. On a device that has one, restoring adds the backup’s notes; a note that exists in both keeps the version changed last.
• Change the password: all notes are sealed again under a new salt and key (you can also pick other key settings). Backups made earlier keep the old password.
• Other tabs: a second tab shows changes made in the first. Changing the password, restoring over the notebook or erasing it locks the other tabs, and a locked tab then asks for the new password (or shows the first page again after an erase), so a tab never writes a note under an old key.

Limitations

• A forgotten password cannot be recovered or reset by anyone, so the notes are lost without it. Keep the password in a password manager and keep a backup.
• The notes live only in this browser on this device. Clearing the site’s data, a private window or a new device mean an empty page until you restore a backup. There is no sync between devices.
• Encryption protects the stored notes. While the notebook is unlocked, the text is on the screen and in memory, and a keylogger, a malicious browser extension or someone looking over your shoulder sees it.
• Plain text only: no images, attachments or formatting. A notebook holds up to 1,000 notes of up to 1,000,000 characters each.
• The Strong key setting needs about 256 MiB of spare memory; a phone may refuse it, and the page then suggests Light.
• Someone who can write to the browser’s storage can delete notes or restore an older sealed copy of one; the encryption detects changes inside a note, not a note being swapped for its own earlier version.

Privacy

On this device: nothing is sent

Your password and notes are handled in this tab. Notes are encrypted before they are stored in this browser; the password and the key are never stored, and nothing is uploaded. Only the auto-lock choices are remembered in this browser.