How LegaKeep Encryption Works

The problem

In January 2026, the DGFIP (France's tax authority) suffered an unauthorized breach of FICOBA, the national bank account database. 1.2 million bank accounts exposed - identities, addresses, banking details. Not a small startup - the French government, with serious security budgets and ANSSI (France's national cybersecurity agency) backing them up.

The word "encrypted" does not mean "private." When services like Google Drive say your files are encrypted, they're right. But they hold the encryption key on their servers. If a hacker reaches those servers, they get the key AND the files. It's like a safe where the owner keeps a spare key under the doormat.

The question isn't if a service will be breached. The question is: what does the hacker get when it happens?

Standard encryption vs zero-knowledge encryption

The difference comes down to one question: who holds the key?

In practice: when you create your LegaKeep vault, you choose a passphrase (a string of words). This passphrase is transformed on your device - phone or browser - into an encryption key using the Argon2id algorithm (64 MB of memory, 3 iterations, 1 thread). This key then protects every document with AES-256-GCM.

Your passphrase never leaves your device. Our servers never receive it. This is not a promise - it is a technical impossibility.

The Breach Simulator

Here's what happens when a document is encrypted by LegaKeep - with real AES-256-GCM output, not an illustration.

The ciphertext above is real AES-256-GCM output from LegaKeep's encryption module. This is not an illustration.

What LegaKeep knows - and doesn't know

We prefer transparency over reassurance. Here is exactly what our servers contain.

Let's be honest

Zero-knowledge encryption doesn't protect you from everything. While your vault is open, your documents are decrypted in the application's memory. But on a modern phone, that memory is isolated: iOS and Android place each application in a sealed compartment (sandbox), preventing any other application from reading LegaKeep's data.

To access that memory, an attacker would need government-grade spyware (like Pegasus, estimated at several million dollars) or physical access to your unlocked phone with specialized forensic tools. To date, no password manager - neither 1Password nor Bitwarden - has suffered a documented memory extraction incident on a phone.

The real risk is simpler: someone picking up your phone while the vault is open. That's why LegaKeep automatically locks your vault after a period of inactivity (30 minutes by default, configurable). On lock, the encryption key is erased from memory. It no longer exists anywhere - not on our servers, not on your device - until you enter your passphrase again.

This model isn't perfect. It's the best known compromise between security and accessibility. The same experts who recommend 1Password for your passwords recommend this architecture for your documents.

Our commitment

We don't ask you to take our word for it. We are going to publish the source code of LegaKeep's encryption module - the code that derives your key, encrypts and decrypts your documents - so that security experts worldwide can verify it and try to break it.

No other digital vault in France does this. Not the big ones, not the small ones. They ask you to trust their institution, their brand, their certifications. We offer you verifiable proof.

This is Kerckhoffs' principle, the same one we applied in our password generator: security relies on the key, not on secrecy of the method. If the code is solid, publishing it makes it stronger.