Zero-knowledge encryption explained

Both phrases appear on a lot of app pages. They are real ideas with specific meanings, but they are also easy to stretch. This page answers the questions people most often have, in order.

What does end-to-end encryption mean?

It describes data that travels. A message or file is encrypted on the sender's device and only decrypted on the recipient's. The servers in between pass it along but cannot read it. Signal and iMessage are well-known examples for messages.

The phrase says nothing about what happens to the data once it arrives, or about metadata such as who talked to whom and when.

What does zero-knowledge mean?

It describes data that is stored. A zero-knowledge service holds your data only in encrypted form, and the key is made from something only you have, such as a password. The company cannot read what it stores, even if it wanted to or was asked to.

The trade-off is real: if you forget the password, the company cannot reset it in any way that brings your data back. That is why such services usually give you a recovery phrase or code.

(In cryptography, "zero-knowledge proof" means something narrower. In app marketing, the phrase almost always means the storage idea above.)

Are they the same thing?

No, though they share a principle: the company in the middle should not hold the key. One is about transit, the other about storage. An app can offer one, both or neither.

How can I tell if an app means it?

A few questions get to the truth quickly:

If I forget my password, can you reset it and keep my data? If yes, they hold a way in, and it is not zero-knowledge.
Is everything encrypted, or only some parts? File names, thumbnails and backups are often exceptions.
Where is encryption done? It should happen on your device, before anything is uploaded.
Has anyone outside the company checked? A published independent audit is the strongest evidence. A planned one is a promise, not proof.
What metadata is kept? Account emails, sign-in times and file sizes can say a lot.

What does neither one protect against?

Someone who has your unlocked phone. A screenshot taken by the person you shared with. Malware on your device that sees content after it is decrypted. Encryption protects data at rest and in transit; it cannot protect what is on a screen in front of the wrong person.

Where does VaultWell fit?

VaultWell, coming soon, has no account and no server holding your vaults, so there is nothing for us to read. Content is encrypted on the phone, the key comes from your path, and the only fallback is a recovery phrase we never see. Backups are encrypted .vwbackup files you keep yourself. An independent security audit is planned; until it is published, that last question on the list above is still open for us too.