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\section*{Homework 6}

\begin{enumerate}
\item Zero-knowledge protocols depend on three main properties called
  completeness, soundness and zero-knowledge.  Explain what they mean?

\item Why do zero-knowledge protocols require an NP-problem as building
  block?

\item Why is it a good choice in a ZKP to flip a coin when requesting a 
  proof from the person who knows the secret?
\end{enumerate}

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