"A. Johnson" <[email protected]> writes:
> Hi George,
>
Hello!
> I recommend a change to the way that these statistics are
> obfuscated. The problem is that new noise is used every day, and from
> the distribution of the reported bins, the exact location within the
> bin (assuming the stat stats constant) can be reported.
>
Assuming that the underlying value is constant and since our Laplace
distribution is public, the adversary can observe which bin is
reported each time and get a probability distribution for the
underlying value.
This indeed seems plausible under the powerful assumption that the
underlying stat is constant.
> So instead of this
>
>> +--------------+ +--------------------+
>> actual value -> |additive noise| -> |round-up obfuscation| -> public
>> statistic
>> +--------------+ +——————————+
>
> I recommend that you flip the order, so that it is like this
> +--------------+ +--------------------+
> actual value -> |round-up obfuscation| -> |additive noise| -> public
> statistic
> +--------------+ +——————————+
>
> “Additive noise” in the context of bins is actually just a distribution over
> bins. You can think of it in two ways:
> 1. Add Laplace noise to the bin center, and then report the bin of the
> resulting number.
Hm, you mean something like this, right?
+--------------+ +--------------------+
+--------------+
actual value -> | binning | -> | addditive noise | -> | binning
| -> public statistic
+--------------+ +——————————----------+
+--------------+
where the additive noise is applied to the center of the first bin?
I can see how this is better, since the underlying value gets
immediately smoothed by binning. However, it does give me a weird
hacky feeling...
Is this construction something that has been used before?
Thanks for the feedback!
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