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Adapts slides for SWITS presentation
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‎slides/Makefile

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FIGS+= tposet.tikz
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FIGS+= trump.jpg
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FIGS+= proofshare.tikz
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FIGS+= Jacobs-method.jpg
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@@ -24,7 +24,7 @@ DEPENDS+= ecurrency.bib
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.PHONY: all
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all: slides-short.pdf
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slides-short.pdf: slides-short.tex preamble.tex ${DEPENDS} ${FIGS}
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slides-short.pdf: slides-short.tex preamble.tex revision.tex ${DEPENDS} ${FIGS}
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slides-short.pdf: idea.tex
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preamble.tex: ../paper/preamble.tex
@@ -46,7 +46,7 @@ clean:
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print: slides-short.pdf
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tposet.tikz: ../fig/tposet.tikz
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trump.jpg: ../fig/trump.jpg
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proofshare.tikz: ../fig/proofshare.tikz
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Jacobs-method.jpg: ../fig/Jacobs-method.jpg
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‎slides/idea.tex

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\mode*
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\section{What's the problem?}
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\begin{frame}
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\centering
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\includegraphics[height=\textheight]{trump.jpg}
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\end{frame}
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\section[Participating]{Participating in a protest}
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\subsection{Joining a protest}
@@ -9,13 +17,6 @@ \subsection{Joining a protest}
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\includegraphics[height=0.5\textheight]{ProtestVerif-join.png}
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\end{frame}
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\begin{frame}
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\begin{align*}
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cid &\gets H(\text{\enquote{WE MUST STAND UP \dots}}) \\
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pid &\gets PRF_{k_P}(cid)
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\end{align*}
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\end{frame}
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\subsection{During in a protest}
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\begin{frame}
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\includegraphics{proofshare.tikz}
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\end{frame}
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\begin{frame}
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\begin{minipage}{\linewidth}
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\begin{align*}
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P\to W\colon & pid \\
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W\leftrightarrow P\colon & \text{perform distance bounding} \\
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W\colon & wid\gets PRF_{k_W}(pid), \\
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& wsig\gets PRF_{k_W}(wid, t_s, l) \\
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W\to P\colon & (wid, t_s, l, wsig) \\
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\end{align*}
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\end{minipage}
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\end{frame}
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\begin{frame}
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% XXX Describe distance bounding
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\centering
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\procedure{Distance-bounding Schnorr}{%
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\textbf{Prover}\colon g, q = |\langle g\rangle|, x\in \ZZ_q
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\> \>
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\textbf{Verifier}\colon g, q, X = g^x \\
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\beta_i \sample \bin, y \sample \ZZ_q
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\> \> \alpha_i \sample \bin \\
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g^y, commit(\beta_1, \dotsc, \beta_n) \> \sendmessageright*{} \> \\
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\> \text{Rapid phase} \> \\
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\> \sendmessageleft*{\alpha_i} \> \\
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\> \sendmessageright*{\beta_i} \> \\
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\> \text{Verification phase} \> \\
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c\gets \alpha_1|\beta_2|\dotsb|\alpha_n|\beta_n \\
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r\gets y + cx \> \sendmessageright*{} \> g^r =^? X^cY\\
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}
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\end{frame}
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\subsection{After the protest}
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\begin{frame}
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\centering
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\includegraphics[height=0.5\textheight]{ProtestVerif-endprotest.png}
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\end{frame}
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\begin{frame}
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\begin{align*}
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\{W, P\}\rightsquigarrow S\colon & H(pid, wid, t_s, l, wsig)
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\end{align*}
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\end{frame}
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\begin{frame}
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\begin{align*}
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W\rightsquigarrow S\colon & (pid, wid, t_s, l, wsig),\\
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& NIZK(wid = PRF_{k_W}(pid), wsig = PRF_{k_W}(wid, t_s, l),\\
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& \exists sign(k_W)) \\
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P\rightsquigarrow S\colon & (pid, wid, t_s, l, wsig),\\
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& NIZK(pid = PRF_{k_P}(cid), \exists sign(k_P))
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\end{align*}
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\end{frame}
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\section[Verifying]{Verifying a protest}
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@@ -94,7 +48,7 @@ \subsection{Verifying proof shares}
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\begin{frame}
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\begin{columns}
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\begin{column}{0.5\linewidth}
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\begin{column}{0.6\linewidth}
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\tiny
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\includegraphics[width=\linewidth]{proofshare.tikz}
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\end{column}
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\subsection{Counting proofs}
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\begin{frame}
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\begin{itemize}
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\item Each \(pid\) with more than \(t\) valid proof shares is counted.
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\item \(t\) is a threshold set to be higher than expected size of collusion
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clusters.
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\end{itemize}
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\begin{example}[No trusted witnesses]
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\begin{itemize}
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\item Each \(pid\) with more than \(t\) valid proof shares is counted.
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\item \(t\) is a threshold set to be higher than expected size of collusion
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clusters.
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\end{itemize}
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\end{example}
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\begin{example}[Trusted witnesses]
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\begin{itemize}
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\item Alternatively, each \(\pid\) with a proof share issued by a trusted
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witness is counted.
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\end{itemize}
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\end{example}
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\end{frame}
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\begin{frame}
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\end{frame}
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\begin{figure}
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\centering
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%\footnotesize
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\begin{minipage}{\linewidth}
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\begin{align*}
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O\to \text{all}\colon & \text{manifesto} \\
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P\colon & t_s\gets \TSget \\
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& \cid\gets \Hash[\text{manifesto}], \\
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& \pid\gets \ACprf[_{\sk_P}][\cid] \\
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W\colon & t_s'\gets \TSget
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\\[-1em]
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\noalign{\hfill Join}
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\midrule
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\noalign{\hfill Participation}
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\\[-3em]
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P\to W\colon & \pid \\
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P\leftrightarrow W\colon &
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\PPK\mleft\{ (\sk_P) : \mright. \\
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& \qquad \pid = \ACprf[_{\sk_P}][\cid], \\
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& \qquad \mleft. \sigma_P' = \ACblind[\ACsign[_{\ssk}][\sk_P]] \mright\}
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\\
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W\colon & \wid\gets \ACprf[_{\sk_W}][\pid] \\
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W\to P\colon & (\wid, t_s', l)
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\\[-1em]
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\noalign{\hfill Participation}
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\midrule
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\noalign{\hfill Submission}
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\\[-2em]
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P\colon & t_e\gets \TSstamp[\Hash[\pid, \wid, t_s, t_s', l]] \\
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W\colon & t_e'\gets \TSstamp[\Hash[\pid, \wid, t_s, t_s', l]] \\
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W\to S\colon & (\pid, \wid, t_s, t_s', t_e, l, \pi_{\wid}),\quad
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\text{where} \\
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& \pi_{\wid} = \SPK\mleft\{ (\sk_W) : \mright. \\
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& \qquad \wid = \ACprf[_{\sk_W}][\pid], \\
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& \qquad \mleft. \sigma_W' = \ACblind[\ACsign[_{\ssk}][\sk_W]]\mright\}
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\\
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& \qquad\qquad (\pid, \wid, t_s, t_s', l) \\
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P\to S\colon & (\cid, \pid, \wid, t_s, t_s', t_e, l, \pi_{\pid}),\quad
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\text{where}\\
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& \pi_{\pid} = \SPK\mleft\{ (\sk_P) : \mright. \\
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& \qquad \pid = \ACprf[_{\sk_P}][\cid], \\
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& \qquad \mleft. \sigma_P' = \ACblind[\ACsign[_{\ssk}][\sk_P]] \mright\}
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\\
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& \qquad\qquad (\cid, \pid, \wid, t_s, t_s', l)
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\end{align*}
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\end{minipage}
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\caption{%
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An overview of the Join, Participation and Submission phases of \PRIVO.\@
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The organizer \(O\) broadcasts the manifesto.
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The protester \(P\), witness \(W\) and their computations are as in \cref{fig:ProofFig}.
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Finally, both \(P\) and \(W\) submits the proof shares to a permanent storage \(S\).
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}%
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\label{fig:ProtocolOverview}
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\end{figure}
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\section{Conclusions}
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\begin{frame}
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\begin{block}{Contributions}
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\begin{itemize}
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\item Distance-bounding Schnorr protocol
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\item \Ie distance-bounding \acs{ZKP} and anonymous credentials
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\item Solves crowd counting in adversarial setting.
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\end{itemize}
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\end{block}
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\end{frame}
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\begin{frame}
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\begin{greenblock}{Possibilities}
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\begin{itemize}
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\item We can implement this by extending BankID.
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\item There are blockchains (ledgers) with reasonable transaction
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throughput, \eg OmniLedger.
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\end{itemize}
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\end{greenblock}
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\begin{alertblock}{Limits}
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\begin{itemize}
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\item Cannot trust results that are pro-government if government issues
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credentials (Sybil).
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\item Requires a chip in smartphones for distance bounding.
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\end{itemize}
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\end{alertblock}
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\end{frame}

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