[karamazov]

The calculations run locally, so your data is secure since it doesn't go anywhere.

The easiest way to check correctness is to compare what Excel returns to what our engine returns. If there's no discrepancy, you can rely on our calculations from then on.

(If there is one, let us know and we'll fix it! We've tested it internally, and part of the goal of the beta is to make sure things hold up in wider use.)

[sgt101]

Data locally == secure : not so much. Do you carry your machine through customs? Do you leave it on your desk at night? Do you leave it in your home (not locked in a safe)? More nightmarish... violence and threats can be applied to individuals with relatively low risk.

Data held on individual responsibility is not secure. To secure it you need an auditable monitored secured database at an alarmed secured location.

Now, bad men may still be able to get at data held by organizations or communes (as sysadmins and security guards are just as worried about car bombs as you and me), but it becomes risky in the way that nabbing someone, extracting their passwords, copying their data, shooting them and burning down their house is not. This is why individuals have long chosen to deposit valuables with trusted third parties rather than keeping it under their beds despite the marginal cost of doing so.

Excel spreadsheets are fundamentally hard to debug, in the sense of understanding the organization of the code is very hard (see GOTO considered harmful), this normally doesn't impact people because spreadsheets tend to be relatively simple, but the problem is that as they become useful and important they tend to become heavily used and more and more complex.

[[EDIT - I just reread this and realized I wrote it as a first person/personal set of statements, and I had no intention of aiming it at any person (especially not the parent author) and so I rewrote it to be impersonal and hopefully not inflammatory or unpleasant]].