# A computer science problem by Rocco Dalto

Computer Science Level pending

Given the matrix $$A= \begin{vmatrix}{4} && {7} && {10} \\ {3} && {19} && {1} \\ {1} && {11} && {2}\end{vmatrix} \bmod{26}$$, use a Hill cipher to decipher the enciphered text $$IWIGPDIXPHSBEAMRDHGLFCZSSHZ$$ using modulo 26, where $$A \rightarrow 0$$, $$B \rightarrow 1$$, $$\ldots$$, $$Z \rightarrow 25$$.

Which one of the 5 choices below is the deciphered message? 

$$A: WE KNOW TODAY IS A REALLY GOOD DAY$$ 

$$B: WHEN YOUR ALIVE EVERY DAY IS A GOOD DAY$$ 

$$C: IS TODAY A REALLY GREAT GREAT DAY$$


$$D: WE KNOW TOMORROW IS NOT A GOOD DAY$$ 

$$E: WHAT IS THE CORRECT ANSWER ABOVE$$.



Write a general program(in any language) to decipher a Hill cipher given the enciphered text and a square matrix. 

The program should not contain any predefined functions or procedures. That is you must create all functions and procedures and they should appear in the program, and not called from a library you created.

Note: For the program $$\gcd(\det(A),26) = 1.$$



This program is a slight modification of the program I wrote in the previous problem.

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