Caesar Cipher:-
Caesar cipher is one of the earliest known and simplest ciphers. It is a type of replacement cipher in which each letter of the plaintext is ‘moved’ to a certain place under the alphabet.
For example, with a shift of 1, A will be replaced by B, B becomes C, and so on.
The name of this method is named after Julius Caesar, who apparently used it to communicate with his generals.
Caesar Cipher Program in C
-
Caesar Cipher Encryption
#include<stdio.h>
int main()
{
char str_message[500], ch;
int j, key;
printf("Enter a message to encrypt: ");
scanf("%s",str_message);
printf("Enter the key: ");
scanf("%d", &key);
for(j = 0; str_message[j] != '\0'; ++j){
ch = str_message[j];
if(ch >= 'a' && ch <= 'z'){
ch = ch + key;
if(ch > 'z'){
ch = ch - 'z' + 'a' - 1;
}
str_message[j] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch + key;
if(ch > 'Z'){
ch = ch - 'Z' + 'A' - 1;
}
str_message[j] = ch;
}
}
printf("Encrypted message: %s", str_message);
return 0;
}
Example:- If you run above program then it will ask to enter the message to encrypt like below:-
Enter a message to encrypt:
walmart.com
Enter the key: –for encrypt your message
5
Encrypted Message is : = bfqrfwy.htr
Enter a message to encrypt:
amazon river
Enter the key: –for encrypt your message
5
Encrypted Message is : = frfets wnajw
-
Caesar Cipher Decryption
#include<stdio.h>
int main()
{
char str_message[500], ch;
int j, key;
printf("Enter a message to decrypt: ");
scanf("%s",str_message);
printf("Enter key: ");
scanf("%d", &key);
for(j = 0; str_message[j] != '\0'; ++j){
ch = str_message[j];
if(ch >= 'a' && ch <= 'z'){
ch = ch - key;
if(ch < 'a'){
ch = ch + 'z' - 'a' + 1;
}
str_message[j] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch - key;
if(ch < 'A'){
ch = ch + 'Z' - 'A' + 1;
}
str_message[j] = ch;
}
}
printf("Decrypted message: %s", str_message);
return 0;
}
Example:- If you run above program then it will ask to enter the message to decrypt like below:-
Enter a message to decrypt:
bfqrfwy.htr
Enter key: –for decrypt your message
5
Decrypted Message : = walmart.com
Enter a message to decrypt:
frfets wnajw
Enter key: –for decrypt your message
5
Decrypted Message : = amazon river
Caesar Cipher Program in C++
-
Caesar Cipher Encryption
#include<iostream>
using namespace std;
int main()
{
char str_message[500], ch;
int j, key;
cout << "Enter a message to encrypt: ";
cin.getline(str_message, 100);
cout << "Enter key: ";
cin >> key;
for(j = 0; str_message[j] != '\0'; ++j){
ch = str_message[j];
if(ch >= 'a' && ch <= 'z'){
ch = ch + key;
if(ch > 'z'){
ch = ch - 'z' + 'a' - 1;
}
str_message[j] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch + key;
if(ch > 'Z'){
ch = ch - 'Z' + 'A' - 1;
}
str_message[j] = ch;
}
}
cout << "Encrypted message: " << str_message;
return 0;
}
Output:-
Example:- If you run above program then it will ask to enter the message to encrypt like below:-
Enter a message to encrypt:
walmart.com
Enter the key: –for encrypt your message
5
Encrypted Message is : = bfqrfwy.htr
Enter a message to encrypt:
amazon river
Enter the key: –for encrypt your message
5
Encrypted Message is : = frfets wnajw
Caesar Cipher Decryption
#include<iostream>
using namespace std;
int main()
{
char str_message[100], ch;
int j, key;
cout << "Enter a message to decrypt: ";
cin.getline(str_message, 100);
cout << "Enter key: ";
cin >> key;
for(j = 0; str_message[j] != '\0'; ++j){
ch = str_message[j];
if(ch >= 'a' && ch <= 'z'){
ch = ch - key;
if(ch < 'a'){
ch = ch + 'z' - 'a' + 1;
}
str_message[j] = ch;
}
else if(ch >= 'A' && ch <= 'Z'){
ch = ch - key;
if(ch > 'a'){
ch = ch + 'Z' - 'A' + 1;
}
str_message[j] = ch;
}
}
cout << "Decrypted message: " << str_message;
return 0;
}
Example:- If you run above program then it will ask to enter the message to decrypt like below:-
Enter a message to decrypt:
bfqrfwy.htr
Enter key: –for decrypt your message
5
Decrypted Message : = walmart.com
Enter a message to decrypt:
frfets wnajw
Enter key: –for decrypt your message
5
Decrypted Message : = amazon river