EncryptText function help. In this assignment you$$ll write a program that encrypts the alphabetic letters in a file using the Hill cipher where the Hill matrix can be any size from $2$x$2$up to $9$x$9.$Your program will take two command line parameters containing the names of the file storing the encryption key and the file to be encrypted. $1\mathrm{.}2\mathrm{.}1$Encryption Key File Formats

The encryption key file will contain a single positive integer, n where $(1<$n $<10),$on the first

line, indicating the number of rows and columns in the encryption matrix. The following n lines

will contain n integers, in each row, in order, of the encryption matrix, separated by spaces.

$1\mathrm{.}2\mathrm{.}2$Encryption Plaintext File Formats

The file to be encrypted can be any valid text file with no more than $9,991$letters in it$.($Thus$,$

it$$s safe to store all characters in the file in a character array of size $10,000,$including any

padding characters.$)$Please note that the input text file will also generally have punctuation,

numbers, special characters, and whitespace in it$,$which should be ignored. You should also

convert uppercase letters to lowercase in the input file, correspondingly lowercase letters do

not need to be converted. Thus, the program will treat A and a the same in your program.

Remember that the input plaintext file may need to be padded to match the block size of the

key. #include

#include

#include

#define MAX$\_$FILE$\_$SIZE $10000$

$//$Function prototypes

void readKeyFile$($char $*$keyFileName$,$int $*$matrixSize$,$int keyMatrix$[][9])$;

int readPlainTextFile$($char $*$plainTextFileName$,$char $*$plainText$)$;

void encryptText$($char $*$plainText$,$int matrixSize, int keyMatrix$[][9])$;

void outputCiphertext$($char $*$ciphertext$)$;

int main$($int argc, char $*$argv$[])\{$

$//$Check for correct number of command line arguments

$$ if $($argc $!=3)\{$

$$ printf$("$Usage: $\%$s

$",$argv$[0])$;

$$ return $1$;

$\}$

$//$Parse command line arguments

$$ char $*$keyFileName $=$argv$[1]$;

$$ char $*$plainTextFileName $=$argv$[2]$;

$//$Variables for key matrix and size

$$ int matrixSize;

$$ int keyMatrix$[9][9]$;

$//$Read encryption key file

$$ readKeyFile$($keyFileName$,$&matrixSize, keyMatrix$)$;

$//$Read plaintext file

$$ char plainText$[$MAX$\_$FILE$\_$SIZE$]$;

$$ int numLetters $=$readPlainTextFile$($plainTextFileName$,$plainText$)$;

$//$Encrypt plaintext

$$ encryptText$($plainText$,$matrixSize$,$ keyMatrix$)$;

$//$Output ciphertext

$$ outputCiphertext$($plainText$)$;

$$ return $0$;

$\}$

$//$Function to read the encryption key file

void readKeyFile$($char $*$keyFileName$,$int $*$matrixSize$,$int keyMatrix$[][9])\{$

$$ FILE $*$keyFile $=$fopen$($keyFileName$,"$r$")$;

$$ if $($keyFile $==$NULL$)\{$

$$ printf$("$Error opening key file.

$")$;

$$ exit$(1)$;

$\}$

$$ fscanf$($keyFile$,"\%$d$",$matrixSize$)$;

$$ if $(*$matrixSize $<2||*$matrixSize $>9)\{$

$$ printf$("$Invalid matrix size.

$")$;

$$ exit$(1)$;

$\}$

$$ for $($int i $=0$; i $<*$matrixSize; i$++)\{$

$$ for $($int j $=0$; j $<*$matrixSize; j$++)\{$

$$ fscanf$($keyFile$,"\%$d$",$&keyMatrix$[$i$][$j$])$;

$\}$

$\}$

$$ fclose$($keyFile$)$;

$\}$

$//$Function to read plaintext file and store only letters in lowercase

int readPlainTextFile$($char $*$plainTextFileName$,$char $*$plainText$)\{$

$$ FILE $*$plainTextFile $=$fopen$($plainTextFileName$,"$r$")$;

$$ if $($plainTextFile $==$NULL$)\{$

$$ printf$("$Error opening plaintext file.

$")$;

$$ exit$(1)$;

$\}$

$$ int index $=0$;

$$ char ch;

$$ while $(($ch $=$fgetc$($plainTextFile$))!=$EOF && index $<$MAX$\_$FILE$\_$SIZE$)\{$

$$ if $($isalpha$($ch$))\{$

$$ plainText$[$index$++]=$tolower$($ch$)$;

$\}$

$\}$

$$ plainText$[$index$]=\text{'}\backslash 0\text{'}$;

$$ fclose$($plainTextFile$)$;

$$ return index; $//$Return the number of letters read

$\}$

$//$Function to encrypt plaintext using Hill cipher

void encryptText$($char $*$plainText$,$int matrixSize, int keyMatrix$[][9])\{$

$//$Implementation of Hill cipher encryption

$//$This part is left for you to implement

$\}$

$//$Function to output ciphertext to the console

void outputCiphertext$($char $*$ciphertext$)\{$

$$ int index $=0$;

$$ while $($ciphertext$[$index$]!=\text{'}\backslash 0\text{'})\{$

$$ printf$("\%$c$",$ciphertext$[$index$])$;

$$ if $(($index $+1)\%80==0)\{$

$$ printf$("$

$")$;

$\}$

$$ index$++$;

$\}$

$\}$