What does end-to-end encryption mean?
Encrypting data means turning it into a form that only someone with the right key can read. “End-to-end” describes where that key lives: only at the endpoints, meaning your devices and (if there is one) the devices of the person you share with.
In a messaging app, end-to-end encryption means only the person you’re talking to can read your messages. In a password manager, both ends are usually you: an item encrypted on your phone is unlocked on your computer, and the server in between only ever sees encrypted data.
How is it different from encryption in transit and at rest?
“Your data is encrypted” can mean very different things. These are the three common models:
- Encryption in transit (TLS/HTTPS): Data is encrypted on its way between your device and the server; once it arrives, the company sees it in the clear. Almost every website uses this.
- Encryption at rest: Data is stored encrypted on disk, but the company holds the keys. This protects against a stolen disk, not against the company itself or someone who breaks into the server.
- End-to-end encryption: Data is encrypted before it even leaves your device, and the key is never given to the company. Whether the server is compromised or the company receives a request for your data, the contents can’t be read.
A good service uses all three together: end-to-end encrypted data that also travels over HTTPS.
How does end-to-end encryption work?
End-to-end encryption combines two kinds of cryptography:
- Symmetric encryption: The same key both encrypts and decrypts. It’s fast, so it’s used to encrypt the data itself. Examples: AES-GCM, XChaCha20-Poly1305.
- Asymmetric (public-key) encryption: There’s a public key that can be shared with anyone and a private key that only its owner holds. To send or share data with someone, you use their public key, and only the holder of the private key can open it. Example: X25519.
Password managers add one more step: the encryption key is usually derived from your master password. This is done with deliberately slow, memory-hungry algorithms such as Argon2id, which makes it very costly for anyone to find your master password by trial and error.
What is zero-knowledge architecture?
Zero-knowledge architecture is the principle that the service provider never knows the user’s data or the key that unlocks it. For a password manager, this means in practice:
- Your master password is never sent to the server. The server only receives a separate verifier derived from it, which is used to sign you in.
- Your vault contents only ever reach the server in encrypted form.
- The company can’t reset your master password, because it doesn’t know it. That isn’t a missing feature; it’s a natural consequence of the model.
What doesn’t end-to-end encryption protect against?
End-to-end encryption is strong protection, but it doesn’t remove every risk. An honest assessment means knowing its limits:
- Metadata: Some information may stay visible on the server so the service can work, such as your email address, the number of items, last-updated times and the devices you’ve signed in from.
- Device security: A device infected with malware can see data once it’s decrypted on screen. Encryption protects your data in transit and on the server, not your device itself.
- A weak master password: Because the key is derived from your master password, a short or guessable master password weakens the protection.
- Phishing: If you type your master password into a fake page, encryption can’t help you. Two-factor authentication and passkeys add an extra layer against this risk.
How does KeyZula implement end-to-end encryption?
In KeyZula, encryption happens on your device, not on the server:
- Your master password is processed on your device with Argon2id (64 MiB of memory, 3 iterations) and turned into a key; the master password itself is never sent to the server.
- Every item has its own random key and is encrypted with XChaCha20-Poly1305. The item’s name, username, website address and type are all part of the encrypted data.
- When you share, the collection key is sealed with the recipient’s X25519 public key, so only that person can open it.
- The information visible on the server (such as your email address, the number of items, organization memberships, and device and IP details) is listed openly on our How it works page.
You can review the design yourself: the encryption library used by every KeyZula client is open source on GitHub, and the detailed threat model is in our security whitepaper (PDF). The source code of the server and apps is closed, and no independent security audit report has been published yet.
Frequently asked questions
Is every site that uses HTTPS end-to-end encrypted?
No. HTTPS only encrypts data in transit; once it reaches the server, it can be processed there in the clear. With end-to-end encryption, data is encrypted on your device before it reaches the server, and the server can’t open it.
Can an end-to-end encrypted service recover my data?
Because only you hold the key, the company can’t reset your master password and unlock your data. In KeyZula, the master password can’t be reset. For business accounts, admin recovery is disclosed to the member and only set up if the member accepts it.
Are zero knowledge and end-to-end encryption the same thing?
They’re closely related. End-to-end encryption describes how the data is protected, while zero knowledge emphasizes that the service provider never knows the data or the key. In password managers, the two usually go hand in hand.
Does end-to-end encryption make my master password more important?
Yes. Your encryption key is derived from your master password, so its strength directly affects how well your vault is protected. Choose a long master password you don’t use anywhere else, and add two-factor authentication to your account.