Tresorit 2.1

Tresorit is an end-to-end encrypted, secure cloud storage and file sharing solution designed to store, sync and share confidential data.
Simply turn any folder to a Tresor and place a file into it and they will automatically sync with every devices connected to the same account.

Encryption is performed before the data gets uploaded to the cloud. Decryption is only possible with permission from the owner and already encrypted contents can be shared without re-encryption, but in a 100 percent secure way.
To prove the security of Tresorit, the company initiated a bounty of $50,000 and invited leading Universities and hackers to breach their service. To date noone has succeeded despite attempts by hundreds including MIT, Stanford, Caltech and Harvard.