*Caeser Cipher: Source Code*
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
public class CeaserCipher {
static Scanner sc=new Scanner(System.in);
static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
public static void main(String[] args) throws IOException {
System.out.print("Enter any String: ");
String str = br.readLine();
System.out.print("Enter the Key: ");
int key = sc.nextInt();
String encrypted = encrypt(str, key);
System.out.println("Encrypted String is: " +encrypted);
String decrypted = decrypt(encrypted, key);
System.out.println("Decrypted String is: " +decrypted);
}
public static String encrypt(String str, int key) {
String encrypted = "";
for (int i = 0; i < str.length(); i++) {
int c = str.charAt(i);
if (Character.isUpperCase(c)) {
c = c + (key % 26);
if (c > 'Z')
c = c - 26;
}
else if (Character.isLowerCase(c)) {
c = c + (key % 26);
if (c > 'z')
c = c - 26;
}
encrypted += (char) c;
}
return encrypted;
}
public static String decrypt(String str, int key) {
String decrypted = "";
for(int i = 0; i < str.length(); i++) {
int c = str.charAt(i);
if (Character.isUpperCase(c)) {
c = c - (key % 26);
if (c < 'A')
c = c + 26;
}
else if (Character.isLowerCase(c)) {
c = c - (key % 26);
if (c < 'a')
c = c + 26;
}
decrypted += (char) c;
}
return decrypted;
}
}
*Output:*
*Enter any String:* Are you feeling better now
*Enter the Key:* 8
*Encrypted String is:* Izm gwc nmmtqvo jmbbmz vwe
*Decrypted String is:* Are you feeling better now
dear students have to do Ceaser Cipher program in CNS lab
*AIM*: Write a Java program to perform encryption and decryption using Hill Cipher
algorithms:
*Hill Cipher: Source Code*
// Java code to implement Hill Cipher
public class Hill
{
// Following function generates the
// key matrix for the key string
public static void getKeyMatrix(String key, int keyMatrix[][])
{
int k = 0;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
keyMatrix[i][j] = (key.charAt(k)) % 65;
k++;
}
}
}
// Following function encrypts the message
public static void encrypt(int cipherMatrix[][],
int keyMatrix[][],
int messageVector[][])
{
int x, i, j;
for (i = 0; i < 3; i++)
{
for (j = 0; j < 1; j++)
{
cipherMatrix[i][j] = 0;
for (x = 0; x < 3; x++)
{
cipherMatrix[i][j] +=
keyMatrix[i][x] * messageVector[x][j];
}
cipherMatrix[i][j] = cipherMatrix[i][j] % 26;
}
}
}
// Function to implement Hill Cipher
public static void HillCipher(String message, String key)
{
// Get key matrix from the key string
int [][]keyMatrix = new int[3][3];
getKeyMatrix(key, keyMatrix);
int [][]messageVector = new int[3][1];
// Generate vector for the message
for (int i = 0; i < 3; i++)
messageVector[i][0] = (message.charAt(i)) % 65;
int [][]cipherMatrix = new int[3][1];
// Following function generates
// the encrypted vector
encrypt(cipherMatrix, keyMatrix, messageVector);
String CipherText="";
// Generate the encrypted text from
// the encrypted vector
for (int i = 0; i < 3; i++)
CipherText += (char)(cipherMatrix[i][0] + 65);
// Finally print the ciphertext
System.out.print(" Ciphertext:" + CipherText);
}
// Driver code
public static void main(String[] args)
{
// Get the message to be encrypted
String message = "ACT";
// Get the key
String key = "GYBNQKURP";
HillCipher(message, key);
}
}
*Output:*
*Ciphertext:* POH
