# 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 encipher the message $$TOMORROW IS NOT A GOOD DAY$$ using modulo 26, where $$A \rightarrow 0$$, $$B \rightarrow 1$$, $$\ldots$$, $$Z \rightarrow 25$$, and enter the result as a string of integers.

Write a general program(in any language) to encipher and decipher a Hill cipher. Check your program by deciphering the enciphered message obtained using the given matrix and plain text message above.

Also, 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 $$\gcd(\det(A),26) = 1.$$

×