So what happens if I lose / don't remember my Master password ? If it's used to encrypt my data I suppose you can't reset it ?
We have chosen a strong security architecture, so we have no way of decrypting your data. If you loose your password, you're screwed. :)
The user's master password is not encrypted, it is used to create the key to encrypt and decrypt user's data, and the encryption key created from the master password, as a derivative of the master password, is never stored or transmitted.
This way, we can assure our users that even us cannot ever access their data.