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#include <stdio.h>
#include <stdlib.h>
//function prototypes
void encrypt(char [], int);
void decrypt(int [], int);
int main()
{
char myString[21] = {0};
int decryptnum[21] = {0};
int iSelection = 0;
int iRand;
srand(time(NULL));
iRand = (rand() % 4) + 1; // random #, 1-4
while ( iSelection != 4 )
{
printf("\n\n1\tEncrypt Clear Text\n");
printf("2\tDecrypt Cipher Text\n");
printf("3\tGenerate New Key\n");
printf("4\tQuit\n");
printf("\nSelect a Cryptography Option: ");
scanf("%d", &iSelection);
switch (iSelection) {
case 1:
printf("\nEnter one word as clear text to encrypt: ");
scanf("%s", myString);
encrypt(myString, iRand);
break;
case 2:
printf("\nEnter cipher text to decrypt: ");
scanf("%d ",decryptnum);
decrypt(decryptnum, iRand);
break;
case 3:
iRand = (rand() % 4) + 1; // random #, 1-4
printf("\nNew Key Generated\n");
break;
} //end switch
} //end loop
} //end main
void encrypt(char sMessage[], int random)
{
int x = 0;
int numChar[21] = {0};
while ( sMessage[x] ) {
numChar[x]=sMessage[x] + random;
x++;
} //end loop
x = 0;
printf("\nEncrypted Message is: ");
//print the encrypted message
while ( numChar[x] ) {
printf("%d ", numChar[x]);
x++;
} //end loop
} //end encrypt function
void decrypt(int numChar[], int random)
{
int x = 0;
char sMessage[21] = {0};
while ( numChar[x] ) {
sMessage[x] = numChar[x] - random;
x++;
} //end loop
sMessage[x] = '\0';
printf("\nDecrypted Message is: ");
//print the decrypted message
while ( sMessage[x] ) {
printf("%c", sMessage[x]);
x++;
} //end loop
} //end decrypt function
