Will I be able to decrypt my files if your service is no longer available?
Our service provides a key for you on-demand, even if you specify your own passphrase or key. So you may wonder what would happen, say, if we were to go out of business and your key was no longer retrievable from our servers.
The answer is that you would still have access to your files, since they are stored on your computer, unencrypted, in the SecretSync folder. Only the files in the tunnel folder under Dropbox would be inaccessible in this scenario. But those are merely encrypted copies of the files in the SecretSync folder.
So the only way for you to lose all your files irrevocably would be if (1) we go out of business and shut off our service, (2) your computer crashes or is destroyed and the files in the SecretSync folder cannot be retrieved, and (3) both of the prior happen simultaneously.
If you use SecretSync to sync more than one computer, the loss of your data is even less likely. In the case where you have two computers synchronizing securely with SecretSync, both computers would have to fail and we would have to cease providing the key from our website all simultaneously. Which I think you can agree is highly unlikely.
Also, if we went out of business, this would more realistically happen with some sort of warning, and we would first notify our users of a cutoff date prior to shutting our service.