iTwin SecureBox is bringing hardware-key based security to Dropbox.
It works by automatically encrypting files dragged into the SecureBox folder, seamlessly integrating with Dropbox without the need for extra steps. Plugging iTwin into a computer automatically decrypts and presents the files that had been encrypted using iTwin SecureBox. Also, it utilizes a 2-factor authentication method - hardware key plus an optional password. With encryption-keys only residing on the iTwin devices, the encrypted files will appear gibberish to anyone who doesn't own the physical device that was used to encrypt.
iTwin SecureBox will be automatically pushed as a free download to all current iTwin users. iTwin can be purchased for US$99 at Amazon.com and iTwin.com.