Question

write a C program which performs encryption and decryption of a message

Answer 1

// C Program for encyption and decryption of message
#include <stdio.h> // Header File

int main()
{
int i, x;
char str[100];

printf("\nPlease enter a string:\t");
gets(str);

printf("\nPlease choose following options:\n");
printf("1 = Encrypt the string.\n");
printf("2 = Decrypt the string.\n");
scanf("%d", &x);

//using switch case
switch(x)
{
case 1:
for(i = 0; (i < 100 && str[i] != '\0'); i++)
str[i] = str[i] + 10; //the key for encryption is 10 that is added to ASCII value

printf("\nEncrypted string: %s\n", str);
break;

case 2:
for(i = 0; (i < 100 && str[i] != '\0'); i++)
str[i] = str[i] - 10; //the key for encryption is 10 that is subtracted to ASCII value

printf("\nDecrypted string: %s\n", str);
break;

default:
printf("\nError\n");
}
return 0;
}

Output Snapshot: