How the encrypted vault works

Your passphrase, the vault key, the recovery key: what each one is for, where it is kept, and why nobody but you can read your documents.

The idea, with a simple picture
The three things to know
What happens when you create it
When you add a document
When you reopen the vault
What is kept where
What the server sees
The limits, stated plainly
Good habits
For the curious: the technical names
Frequently asked questions

1. The idea, with a simple picture

Encrypting a document means scrambling it with a key. Without the key, all you see is a meaningless string of characters. With the key, you get the exact document back.

The storage unit pictureYou put your papers in a trunk, lock it at home, then leave it at a storage company. The attendant stores the trunk, can weigh it and count how many you have, but has no key: the trunk cannot be opened.

The vault of My documents works the same way. Encryption happens in your browser, on your device, before anything is sent. What goes to the server is already unreadable. This is called “end-to-end” or “client-side” encryption.

The key never leaves your device in readable form. The server keeps locked trunks, never the key.

2. The three things to know

The passphraseFour or five words that you choose and remember. It is stored nowhere: it exists only in your head.

The vault keyA key drawn at random by your browser, far too long to remember. This is what really encrypts your documents.

The recovery keyThe vault key, written out in letters and digits, shown only once at creation. It is your spare, to be kept somewhere else.

Why two keys, and not just the passphrase?

A phrase you can remember is always weaker than a key drawn at random. So the vault uses both, each for what it does well:

the vault key, very strong, encrypts the documents;
the passphrase is used to shut that key inside a small locked box, which we will call the envelope.

The key safe pictureThink of the small combination boxes fixed next to a front door: the real house key is inside, and your code opens the box. Here, the passphrase is the code, the envelope is the box, and the vault key is the house key.

This arrangement has a practical benefit: to change your passphrase, only the envelope has to be redone. Your documents are not re-encrypted one by one, and the change is immediate.

3. What happens when you create the vault

You type your passphrase twice (at least 12 characters).
Your browser draws the vault key at random: 256 coin tosses in a row.
It turns your passphrase into a locking key, using a deliberately slow calculation repeated 310,000 times. For you, that takes less than a second. For someone trying millions of phrases, every single attempt costs that same time.
With this locking key, it closes the envelope that holds the vault key.
It stores the envelope: on the server for an account vault, in the browser for a vault on the device.
It shows you the recovery key, once only. You copy it, print it or save it to a file, then confirm that you have put it somewhere safe.

Neither the passphrase, nor the readable vault key, nor the recovery key is sent to the server.

4. When you add a document

On your device

The document is read: the text of the PDF, or the scan is recognised.
Its record is prepared: type, date, amount, due date.
The document is encrypted with the vault key.
The list of your documents (names, records, recognised text) is encrypted too.

On the server (“plus” account)

One unreadable file per document, named with a random number.
One unreadable file for the list.
The envelope, closed by your passphrase.

Reading the text, recognising scans, searching and filing all happen in your browser. The server reads nothing, because it cannot read anything.

Each document is encrypted with a different “pinch of salt” drawn at random: two identical documents produce two encrypted files with nothing in common. Encryption also acts as a seal: if a file were altered on the server, even by a single character, your browser would refuse to open it.

5. When you reopen the vault

The page fetches the envelope.
You type your passphrase. The browser redoes the slow calculation and tries to open the envelope.
If the passphrase is wrong, the envelope does not open: that is how the page knows the phrase is wrong, without anyone knowing the right one.
If it is right, the vault key comes out of the envelope and stays in the memory of the tab for the length of your visit.
The list is decrypted and displayed. A document is only downloaded and decrypted when you open it.

As soon as you close or reload the page, the key vanishes from memory. That is why the passphrase is asked for at every visit: it is not an oversight, it is the protection.

With the recovery key, the envelope is skipped: you hand over the vault key directly. The page checks that it is the right one using a fingerprint, then opens the vault in the same way.

6. What is kept where

“Plus” account vault

Item	Where	In what form
Your documents	ressources.online server, in a folder reserved for your account	Encrypted, unreadable without the vault key
The list and the records	Same folder	Encrypted
The envelope	Same folder	Closed by your passphrase
The readable vault key	Memory of the tab, during the visit	Never written to disk, never sent
The passphrase	Nowhere	In your head
The recovery key	Wherever you put it	Readable: it is up to you to protect it

Nothing is kept on your computer for an account vault, except the recovery key file if you chose to save it: it is then in your Downloads folder.

Vault on the device (without a “plus” account)

The same items, in the same forms, but in your browser's storage for the site, on this device. Nothing goes to the server. In return, the vault disappears if you clear the browser's site data, and it cannot be seen from another device.

7. What the server sees, and what it does not

It sees

that your account has a vault;
the number of encrypted files;
their approximate size;
the date each one was stored.

It does not see

the content of the documents;
their names;
their records, tags and amounts;
the text recognised in scans;
your passphrase, the vault key, the recovery key.

The vault folder is closed to web addresses: a file only goes out to the signed-in account it belongs to. And even if it did get out, it would remain unreadable.

A direct consequence: we cannot “reset” your passphrase the way a password is reset. We hold no copy of anything.

8. The limits, stated plainly

Passphrase and recovery key both lost: the documents are lost. Nobody can reopen them, including us. That is the price of a vault we cannot read.
A weak passphrase is still a weakness. The slow calculation hinders guessing, it does not prevent it. “password123” can be guessed; four or five unrelated words cannot.
An infected device sees what you see. Spyware on your computer can read what you type and what is displayed. Encryption protects what is stored and what travels, not a compromised device.
A vault left open is open. As long as the tab stays open, anyone in front of the screen can reach the documents.
You are trusting the page. Encryption is done by the program the site sends to your browser. As with any online service, this assumes the program does what is described here.
The recovery key opens everything. Kept in a file on the same computer, it cancels part of the protection.

9. Good habits

Choose a passphrase of four or five unrelated words that you use nowhere else. The Password checker tool suggests some.
Print the recovery key and keep it with your important papers, or on a USB stick that is put away. Then delete the file from the Downloads folder.
Close the tab when you have finished, especially on a shared computer.
Keep the original of any important document somewhere else: a vault does not replace a backup.
If you think someone knows your passphrase, change it in the “Vault security” part of the vault.

10. For the curious: the technical names

On this page	Technical name
Encryption of the documents and the list	AES-GCM, 256-bit key
The “pinch of salt” of each file	Random 96-bit initialisation vector, placed at the start of the file
The seal	GCM authentication tag
The slow calculation on the passphrase	PBKDF2 with SHA-256, 310,000 iterations, random 128-bit salt
The envelope	Vault key encrypted with AES-GCM by the key derived from the passphrase (key wrapping)
The recovery key	The 256 bits of the vault key, in hexadecimal, in groups of four
The verification fingerprint	SHA-256 of the vault key followed by a fixed text
Randomness	The browser's generator, `crypto.getRandomValues`
The encryption engine	Web Crypto, built into the browser; the key is imported there as non-exportable
Storage on the device	IndexedDB, database `ro-coffre`

These are public, widely used methods, the same ones password managers rely on. Nothing is invented here: in encryption, good practice is to assemble known, proven building blocks.

11. Frequently asked questions

Where is the encryption key stored on my computer?

For an account vault, nowhere: it only exists in readable form in the memory of the tab, during the visit. For a vault on the device, the browser keeps the envelope, that is, the key closed by your passphrase, never the readable key.

Could you read my documents if a court or a hacker asked you for them?

We can only hand over what we have: encrypted files and a closed envelope. Without your passphrase or your recovery key, they are useless.

I have forgotten my passphrase. What should I do?

On the opening screen, choose “I forgot my passphrase: use my recovery key”. Once inside, set a new passphrase in the “Vault security” part.

If I change my passphrase, does the old one still work?

No. The envelope is redone with the new passphrase, and the old one no longer opens it. The recovery key stays the same.

Why is the passphrase asked for at every visit?

Because the key is kept nowhere between two visits. Keeping it would save retyping the phrase, but it would then be within reach of anyone using the device.

Search works even though everything is encrypted: how?

The list and the text of your documents are decrypted in your browser when the vault opens. The search happens there, on your device. The server takes no part in it.

Can an assistant or an AI read my vault?

Only in your browser, with the vault opened by you, and it can only suggest: every filing suggestion waits for your approval. The vault itself sends nothing to any outside service.

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