"A. Johnson" <[email protected]> writes: > Hello all, > > <snip> > >> We put in some simple obfuscations in order to not reveal too >> sensitive data: we multiplied actual values with a random number in >> [0.9, 1.1] before including those obfuscated values in extra-info >> descriptors. Maybe there's something smarter we could do? Or is this >> okay? > > I actually think that additive rather than multiplicative noise > (i.e. randomness) makes sense here. Let’s suppose that you would like > to obscure any individual connection that contains C cells or fewer > (obscuring extremely and unusually large connections seems hopeless > but unnecessary). That is, you don’t want the (distribution of) the RP > cellcount from any relay to change by much whether or not C cells are > removed The standard differential privacy approach would be to *add* > noise from the Laplace distribution Lab(\epsilon/C), where \epsilon > controls how much the statistics *distribution* can multiplicatively > differ. I’m not saying that we need to add noise exactly from that > distribution (maybe we weaken the guarantee slightly to get better > accuracy), but the same idea applies. This would apply the same to > both large and small relays. You *want* to learn roughly how much RP > traffic each relay has - you just want to obscure the exact number > within some tolerance. >
Hello Aaron, I posted an initial draft of the proposal here: https://lists.torproject.org/pipermail/tor-dev/2014-November/007863.html Any feedback would be awesome. Specifically, I would be interested in undertanding the concept of additive noise a bit better. As you can see the proposal draft is still using multiplicative noise, and if you think that additive is better we should change it. Unfortunately, I couldn't find any good resources on the Internet explaining the difference between additive and multiplicative noise. Could you expand a bit on what you said above? Or link to a paper that explains more? Or link to some other system that is doing additive noise (or even better its implementation)? Thanks! _______________________________________________ tor-dev mailing list [email protected] https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev
