How Filarr protects your data

Encryption in plain words: what stays secret, what Filarr's servers can and cannot see, and what it means if you lose your password.

On this page
Documentation sections

Filarr encrypts your files and notes on your own device, before anything is sent anywhere. This page explains what that means in everyday words, what Filarr's servers can see, what they never see, and where this protection stops.

A safe and its key

Picture a safe. You put your documents inside, close the door and keep the key. Filarr can store the safe, carry it from one of your devices to another and keep a spare copy. Filarr also keeps a copy of the key, but locked in a small box that only your password, or your recovery phrase, can open. Filarr doesn't keep your password or your phrase. Without one of them, the safe is a box of scrambled data that nobody can read.

In Filarr:

  • the safe is your files and notes, turned into unreadable data. This is what "encrypted" means;
  • the key is a long secret number that Filarr creates for your local profile, or for your cloud account;
  • your password locks that key away. Only your password, or your recovery phrase, can take it out.

What happens when you save a file

  1. You add a file or write a note.
  2. Filarr encrypts it on your computer, or in your browser in the web app, using your key.
  3. If you use sync, only the encrypted version travels to Filarr's servers.
  4. Your other devices download the encrypted version and open it with the same key.

Your key never travels in readable form. Filarr unlocks it with your password, on your own device. When you change your password, Filarr only changes the lock around the key. Your files are not encrypted again, which is why the change is instant.

You can check that encryption is on in Settings → Security: the Encryption row shows AES-256-GCM and the Encryption key row shows Active.

What Filarr's servers can see

To sync and share, the servers need some information. Here is what they see:

  • your account email address, and your display name and @handle if you set them;
  • your plan and your payment status. Payments themselves go through Stripe, or through your phone's app store for a purchase made in the mobile app;
  • your contacts, and the invitations you send or receive;
  • your devices (their name, their system, their last activity) and your sign-ins;
  • your account password, each time you type it for the server: when you create your account, sign in, change your password or confirm a sensitive action. The connection is encrypted (HTTPS) on the way;
  • your 24-word account recovery phrase: the server creates it, sends it to you when you create your account or ask for a new one, and receives it again when you use it;
  • your key, locked twice: once by your password and once by your recovery phrase. This locked copy is what lets a new device open your data;
  • the encrypted data, its size and the space you use;
  • technical identifiers: random codes that name each file or vault without describing it;
  • who belongs to which shared vault, with which role;
  • activity without content: for example, that a share link was downloaded, or that someone mentioned you in a vault;
  • your IP address, as with any website. For the downloads of a share link, the download history keeps only a rough network range and the country. The full address is kept for a short time to limit abuse, and when a link is reported for serious illegal content.

The server keeps your password and your account phrase only as a one-way fingerprint (a hash). A fingerprint lets it check what you type, but it cannot be turned back into the password or the phrase.

Where this protection stops

The password and the phrase that unlock your key are the same ones the server receives. Filarr's server only checks them and doesn't keep them. But a server that had been tampered with could capture them as they arrive, and then unlock your key. A stolen copy of Filarr's database, on the other hand, opens nothing without your password or your phrase.

What Filarr's servers never see

  • the content of your files and notes;
  • the names of your files and folders, and the titles of your notes;
  • the names of your shared vaults and of your share links;
  • the 12-word recovery phrase of a local profile, which never leaves your device;
  • your encryption key in readable form. The server keeps it only locked, by your password and by your recovery phrase (see the limit above).

Filarr also cannot reset a cloud account's password by email. That reset would leave your files locked under the old password, so the server refuses it and points you to your 24-word phrase.

Shared vaults

A shared vault has its own key. Each member has a personal pair of keys, created on their device. When someone joins, Filarr seals the vault key for that person: only their personal key can open it. Filarr passes the sealed key along. It stores each member's personal key only locked, like your file key, by that member's password and recovery phrase.

When you remove a member, Filarr gives the vault a new key and seals it again for the people who stay. The person who left keeps what they already downloaded, but cannot read anything added afterwards.

To make sure a key really belongs to the person you think, compare your safety numbers. Invite people and manage members shows how.

When you share a file by link, the key that opens it is part of the link, after the # sign. Browsers never send that part of an address to a server. Filarr stores the encrypted file but cannot open it. Anyone who has the full link can, so send it only to the right person, through a channel you trust. Pages published from a note work the same way.

What this means for you

Without your password or your recovery phrase, nobody can open your data, Filarr included. It is the whole point, and it has a direct consequence:

  • if you forget your password, your recovery phrase lets you choose a new one;
  • if you lose your password and your recovery phrase, your data is lost for good. Filarr cannot reopen it for you, and neither can anyone else.

An organization's administrators cannot read your personal files either. Filarr holds no master key that opens every account.

For the curious

  • Each local profile, or each cloud account, has a random 256-bit key. Files and notes are encrypted with AES-256-GCM, with a new random value for each file.
  • Your password becomes a locking key through PBKDF2-SHA-512 with 600,000 rounds. That locking key wraps your file key. Changing the password rewraps the file key and rewrites nothing else. A second copy of the file key is wrapped the same way under your 24-word phrase.
  • Your account password goes to the server over HTTPS and is checked there against a bcrypt hash. The 24-word phrase is generated by the server and reaches your device over HTTPS.
  • Each account has an X25519 key pair to seal shared vault keys, and an Ed25519 key pair that serves as its identity. The safety number is derived from that identity.
  • In the desktop app, the file key is kept sealed by your operating system's secure storage, for your user account, unless you turn on Enhanced lock. In the web app, it stays in memory by default. Stay unlocked on this device (14 days) keeps it sealed under a browser key that cannot be exported.
  • Removing a vault member rotates the vault key: revocation works forward only.
  • A share link looks like https://filarr.com/s/…#k=…. The part after # is the key.
  • In the web app, Settings → Security → Web security model → Read the page explains what the browser version guarantees, and what it cannot.