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\textit{Oh, an empty article!}
You can \input{macros.tex}
\begin{document}
\centerline{\large \bf CS/MATH111 ASSIGNMENT 2}
\centerline{due Tuesday, April~29 (8AM)}
\vskip 0.1in
\noindent{\bf Individual assignment:} Problems 1 and 2.
\noindent{\bf Group assignment:} Problems 1,2 and 3.
\vskip 0.1in
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{problem}
Let $x$ be a positive integer and $y = x^2+2$. Can $x$ and $y$ be both prime? The answer is yes,
since for $x=3$ we get
started by \textbf{double clicking} this text block and begin editing. You can also click the \textbf{Insert} button below to add new block elements. Or you can \textbf{drag and drop an image} right onto $y=11$, and both numbers are prime. Prove that this
text. Happy writing! is the only value of
$x$ for which both $x$ and $y$ are prime.
\smallskip
\noindent\emph{Hint:} Consider cases, depending on the remainder of $x$ modulo $3$.
\end{problem}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{problem}
Alice's RSA public key is $P = (e,n) = (13,77)$.
Bob sends Alice the message by encoding it as follows.
First he assigns numbers to characters:
blank is 2, comma is 3, period is 4, then
A is 5, B is 6, ..., Y is 29, and Z is 30. Then he
uses RSA to encode each number separately.
\smallskip
Bob's encoded message is:
\begin{verbatim}
11 58 52 30 57 61
60 22 30 10 26 35
52 23 30 10 41 22
23 52 38 30 52 12
58 46 30 57 61 60
30 35 26 46 30 50
41 23 52 61 22 52
30 52 12 58 73 30
26 23 30 57 61 60
30 69 37 58 26 23
58 53
\end{verbatim}
Decode Bob's message. Notice that you don't have Bob's secret key, so you
need to ``break" RSA to decrypt his message.
\smallskip
For the solution, you need to provide the following:
%
\begin{itemize}
%
\item Describe step by step how you arrived at the solution:
\begin{itemize}
\item Show how you determined $p$, $q$, $\phi(n)$, and $d$;
\item Show the computation for the first number in the message.
\end{itemize}
%
\item Give Bob's message in plaintext. (The message is a quote. Who said it?)
%
\item If you wrote a program, attach your code to the hard copy.
If you solved it by hand, attach your scratch paper with calculations.
%
\end{itemize}
\end{problem}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{problem}
(a) Compute $14^{-1}\pmod{19}$ by enumerating multiples of the number and the modulus.
Show your work.
\smallskip\noindent
(b) Compute $14^{-1}\pmod{19}$ using Fermat's theorem. Show your work.
\smallskip\noindent
(c) Find a number $x\in\braced{1,2,...,40}$
such that $7x \equiv 11 \pmod{41}$. Show your work.
(You need to follow the method covered in class; brute-force checking
all values of $x$ will not be accepted.)
\end{problem}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\vskip 0.1in
\paragraph{Submission.}
To submit the homework, you need to upload the pdf file into ilearn by 8AM on Tuesday,
April~29, and turn-in a paper copy in class.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\end{document}