We use data which you actively enter (for instance, your profile data when you register for the professional version). Because of the correctness guarantee, as part of every calculation, we encrypt account data (and other data entered for calculations) using a public key and store them for 2 months. The private key is not on the server, thus even if a hacker would break into the server within 2 months after data have been entered, he could not read them. When you perform mass calculations, you have control over when the data are deleted; you can delete your file from the server immediately once you are certain you no longer need it. Mass calculation data are not encrypted since otherwise you would not be able to download the results in legible form.