Probably something like this http://zeroknowledgeprivacy.org/

Yeah, a made-up term that was ripped off from http://en.wikipedia.org/wiki/Zero-knowledge_proof because it sounded high-tech, yet has nothing to do with ZKP and merely means "you encrypt everything client-side and we store binary blobs on the server for you".

I see so this works similar to how blockchain.info site works in the browser, with the server used for encrypted backups and to retrieve blockchain data.

Thanks for answering

We actually based the Lavaboom Sync functionality on blockchain.info's model - the private keys are encrypted using user's plaintext password, while the client only sends the password's hash to the server during authentication.

As glibgil says, it's called Zero Knowledge and it means we can't access your data because it's encrypted client-side. It was a no-brainer, since we already have your public key.

We make key management easier by offering the option to enable Lavaboom Sync, basically your public and (encrypted) private keys stay on our server and get downloaded on login.