How TakeNote protects your notes

1The short version

Your notes are encrypted on your device before they are sent. Our server only ever stores sealed notes, so someone who gets a copy of our database or our backups cannot read them. Your private keys are made on your device and never leave it, and if you forget your passphrase no one can recover it.

TakeNote does not hide everything. Who receives each note, when, and how big it is are visible to whoever runs the service. And the protection relies on the public keys our server hands out being real, which the extension cannot check for itself. The sections below say exactly what that means.

2How a note is protected

Setup. The extension makes two pairs of keys on your device: one pair seals and opens notes (RSA, 4096-bit) and the other signs them (ECDSA, P-256). Each pair has a public key, which other people use, and a private key, which stays on your device.
Sealing. To send a note, your extension asks our server for the recipient's public key. It makes a fresh one-time key and uses it to encrypt your subject, your message, your username and the time (AES-256-GCM, which also detects any tampering). It then seals that one-time key with the recipient's public key (RSA-OAEP with SHA-256), so only their private key can open it.
Signing. Inside the sealed note, your extension adds a signature made with your signing key. The recipient's extension checks it, so a note that was changed on the way, or whose sender name was changed, fails the check.
Sealed sender. Your username is inside the sealed note rather than on the outside, so a stored note does not say who sent it.
Delivery. The recipient's extension collects the note, opens it with the private key on their device, and confirms. Our server then deletes its copy.

3What our server can and cannot see

Our server cannot see:

the subject or the text of any note;
who sent a note that is stored, because the name is inside the sealed note;
your private keys;
your passphrase or your PIN.

Our server can see:

your email address;
your username, stored encrypted with a key our server holds, so our server can read it;
your public keys;
your IP address and browser details, in our providers' logs for about a week;
who receives each note, when, and how big it is;
who is sending, as it happens, because you are signed in when you send;
two counts per account per day, to limit abuse: how many notes you sent, and how many username lookups failed. We never record who you sent to or which names you looked up. Both counts are deleted after 2 days.

4Your keys and your passphrase

Your private keys are created on your device and never leave it. We do not hold a copy, so we cannot read your notes and cannot restore them for you.
On your device they are stored encrypted with your passphrase. The passphrase is stretched with PBKDF2 (SHA-256, 600,000 rounds) and the keys are encrypted with AES-256-GCM. A passphrase must be at least 12 characters.
TakeNote locks itself after 15 minutes without use, and asks for your passphrase at least every 8 hours.
If you forget your passphrase, no one can recover it, and the notes on that device cannot be read again. That is on purpose. "Reset this device" lets you start over: you keep your account and username, but the keys and notes on that browser are removed.
Your PIN unlocks TakeNote quickly during a browser session. It is a lock against someone at your keyboard, not against software that can read the memory of your browser.
Your keys exist only in the browser where you created them. Nothing is synced, and your account is active in one browser at a time.

5What the extension can access

TakeNote asks Chrome for three permissions: storage, to keep your keys and notes on your device; alarms, to lock itself on time; and offscreen, to play the arrival sound. It can talk to two places: our server, and the app.takenote.fyi pages where you sign in. It does not ask for access to your browsing history, your tabs or other websites, and it does not use Chrome sync.

6Where the protection ends

The public keys come from our server.: When you send a note to a username, our server tells your extension which public key belongs to that name, and the extension has no other way to check it. So if an attacker took over our server, they could hand out a false key, read notes sent after that, or make a note appear to come from someone it did not. They could not read notes sent before that. The same limit applies to us as the operator.
The extension must be the genuine one.: Everything on this page relies on the extension on your device being the one we published.
Who you talk to is not hidden.: The sender's name is sealed inside the note, so a stored note does not say who sent it. But you are signed in when you send, so the running service sees who is sending, and who receives each note, when, and how big it is are visible to our server. Where few people send on the same day, the daily counts can narrow down who sent a given note.
Your device.: Notes are readable on your device once TakeNote is unlocked. Software that can read your browser's memory, or someone using your unlocked browser, can read them.
Your account.: Anyone who has your password, or who controls your email and uses it to reset the password, can move your account to their own browser. They would receive your new notes and could send notes as you. They could not read notes already on your device. Use a strong password you use nowhere else.
Once a note has arrived.: What a recipient does with a note on their device is up to them. They can copy it, photograph it or forward it.
Outside review.: TakeNote has been reviewed by its developer but has not been independently audited.

7How long things are kept

Clean-up runs once a day, so each time below can run up to about a day longer.

A note you receive is deleted from our server as soon as your device confirms it has it.
A note that is never collected is deleted about 7 days after it was sent.
Notes on your device are removed after 7 days.
The daily counts are deleted after 2 days.
When you delete your account, your account, keys and waiting notes are removed at once. One thing is kept: your username, as a one-way code that cannot be turned back into your name, so nobody can take your name later and send notes that appear to be from you.

The full detail, and the companies that handle parts of the service, are in the Terms of Service.

8Questions, or a problem to report

Email support@takenote.fyi. If you think you have found a security problem, please say so in the subject line and give us time to fix it before you share the details.