Ceaser Cipher Java Implementation

Ceaser Cipher Java Implementation

The Caesar cipher, also known as a shift cipher, is one of the simplest forms of encryption. It is a substitution cipher where each letter in the original message (called the plaintext) is replaced with a letter corresponding to a certain number of letters up or down in the alphabet.

In this way, a message that initially was quite readable, ends up in a form that can not be understood at a simple glance.

For example, here's the Caesar Cipher encryption of a message, using a right shift of 3.

Plaintext:  
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
Ciphertext: 
QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD

Encryption:  c=(m+k)mod 26

Decryption: m=(c-k+26)mod 26

source code:

package ceaser;


import java.util.Scanner;

public class Ceaser {

 
 
 
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  
  System.out.println("Enter the plaintext:");
  Scanner in =new Scanner(System.in);
  String str=in.nextLine();
  Ceaser.encryption(str);
  System.out.println("Enter the ciphertext:");
  str=in.nextLine();
  Ceaser.decryption(str);
  
  

 }
 

 
 public static void encryption(String str){
 String en="";  
  for(int i=0;i<str.length();i++){
   
     char ch = (char) (((int)str.charAt(i) +3 - 97) % 26 + 97);
   
     en +=ch;
   
   
  }
  System.out.println("The ciphertext is:"+en);
  
 }
 public static void decryption(String str){
  
 
  String en="";  
  for(int i=0;i<str.length();i++){
   
     char ch = (char) (((int)str.charAt(i) -3 +26 -97) % 26 + 97);
   
     en +=ch;
   
   
  }
  System.out.println("The ciphertext is:"+en);
 
 
 }
 

}

Output:

Enter the plaintext:
patancampus
The ciphertext is:sdwdqfdpsxv
Enter the ciphertext:
ghimireshankar
The ciphertext is:defjfobpexkhxo