CastleSoft is serious about security:

You can be confident that all our software uses the very latest security techniques, which include SSL, SSH, AES256, and Database encryption.

CastleSoft secures your data by encrypting it when it’s sent over the Internet, storing it in an encrypted format when kept on server, and using secure tokens for authentication. This means that your data is protected from unauthorized access both while it is being transmitted to your devices and when it is stored in the cloud. CastleSoft uses a minimum of 256-bit AES encryption the same level of security employed by major financial institutions and never provides encryption keys to any third parties.