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\section*{Homework 8}

\begin{enumerate}
\item (\textbf{Optional}) How can the hardness of the
      proof-of-work puzzles in Bitcoins be adjusted? What is
      parameter that determines how the hardness is adjusted?

\item (\textbf{Optional}) What is the main data that is stored
      in Bitcoin's blockchain? 
      
\item (\textbf{Optional}) What is is the purpose of the
      proof-of-work puzzle in Bitcoins?      

\item (\textbf{Optional}) The department has large labs full
      of computers that are pretty much idle over night. Why
      is it a bad idea to let them mine for Bitcoins?

\end{enumerate}
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