From 3be8267c2f2a70020d83de213d2828335a7c5b09 Mon Sep 17 00:00:00 2001 From: Manos Date: Tue, 12 Oct 2021 13:00:26 +0200 Subject: [PATCH] problem: Additional remarks in lmdk-sel-sol --- text/problem/theotherthing/solution.tex | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/text/problem/theotherthing/solution.tex b/text/problem/theotherthing/solution.tex index fe37676..44e4afe 100644 --- a/text/problem/theotherthing/solution.tex +++ b/text/problem/theotherthing/solution.tex @@ -186,7 +186,7 @@ For every possible histogram version, the \getDiff function finds the difference \Return{\opts} \end{algorithm} -Between Lines~{\ref{algo:lmdk-sel-hist-cmp-start}-\ref{algo:lmdk-sel-hist-cmp-end}} we check every possible histogram version by incrementing each bin by $1$ and comparing it to the original (Line~\ref{algo:lmdk-sel-hist-cmp}). +In Lines~{\ref{algo:lmdk-sel-hist-cmp-start}-\ref{algo:lmdk-sel-hist-cmp-end}} we check every possible histogram version by incrementing each bin by $1$ and comparing it to the original (Line~\ref{algo:lmdk-sel-hist-cmp}). In the end of the process, we return \opts which contains all the versions of \hist that are closest to \hist for all possible sizes of \hist. @@ -195,6 +195,9 @@ In the end of the process, we return \opts which contains all the versions of \h The Algorithms of Section~\ref{subsec:lmdk-set-opts} return a set of possible versions of the original {\thething} set $L$ by adding extra timestamps in it from the series of events at timestamps $T \supseteq L$. In the next step of the process, we randomly select a set by utilizing the exponential mechanism (Section~\ref{subsec:prv-mech}). + + +\paragraph{Score function} Prior to selecting a set, the exponential mechanism evaluates each set using a score function. One way evaluate each set is by taking into account the temporal position the events in the sequence. @@ -215,3 +218,9 @@ On the one hand, sets with more dummy {\thethings} may render actual {\thethings That is due to the fact that, it is harder for an adversary to pick a {\thething} when the ratio of {\thethings} to the size of the set gets lower. On the other hand, more dummy {\thethings} lead to distributing the privacy budget to more events, and therefore investing less at each timestamp. Thus, providing a better level of privacy protection. + + +\paragraph{Option release} +The options that Algorithms~\ref{algo:lmdk-sel-opt} and \ref{algo:lmdk-sel-heur} generate contain actual timestamps which can be utilized directly by the {\thething} privacy mechanisms that we presented in Section~\ref{subsec:lmdk-mechs}. +However, Algorithm~\ref{algo:lmdk-sel-hist} returns histograms instead of timestamps. +Therefore, we need to process the result of the exponential mechanism further by creating a sample from the true {\thethings} and populating it with the remaining amount of choices, i.e.,~$\left|L'\right| - \left|L\right|$ by performing sampling without replacement from the resulting option $L$.