Untitled

import java.io.*;
import java.util.Scanner;

public class HillCipher {
    static double[][] decrypt = new double[3][1];
    static double[][] a = new double[3][3];
    static double[][] b = new double[3][3];
    static double[][] mes = new double[3][1];
    static double[][] res = new double[3][1];
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        getkeymes();

        // Encryption
        for (int i = 0; i < 3; i++)
            for (int j = 0; j < 1; j++)
                for (int k = 0; k < 3; k++)
                    res[i][j] += a[i][k] * mes[k][j];

        System.out.print("\nEncrypted string is: ");
        for (int i = 0; i < 3; i++) {
            System.out.print((char) (res[i][0] % 26 + 97));
        }

        // Inverse key matrix
        inverse();

        // Decryption
        for (int i = 0; i < 3; i++)
            for (int j = 0; j < 1; j++)
                for (int k = 0; k < 3; k++)
                    decrypt[i][j] += b[i][k] * res[k][j];

        System.out.print("\nDecrypted string is: ");
        for (int i = 0; i < 3; i++) {
            System.out.print((char) (Math.round(decrypt[i][0]) % 26 + 97));
        }
        System.out.print("\n");
    }

    public static void getkeymes() throws IOException {
        System.out.println("Enter 3x3 matrix for key (It should be invertible): ");
        for (int i = 0; i < 3; i++)
            for (int j = 0; j < 3; j++)
                a[i][j] = sc.nextDouble();

        System.out.print("\nEnter a 3-letter string: ");
        String msg = br.readLine();
        if (msg.length() != 3) {
            throw new IllegalArgumentException("Input must be exactly 3 letters.");
        }

        for (int i = 0; i < 3; i++)
            mes[i][0] = msg.charAt(i) - 97;
    }

    public static void inverse() {
        double p, q;
        double[][] c = new double[3][3];

        // Copy matrix a to c
        for (int i = 0; i < 3; i++)
            System.arraycopy(a[i], 0, c[i], 0, 3);

        // Initialize identity matrix for b
        for (int i = 0; i < 3; i++)
            for (int j = 0; j < 3; j++)
                b[i][j] = (i == j) ? 1 : 0;

        // Perform matrix inversion
        for (int k = 0; k < 3; k++) {
            for (int i = 0; i < 3; i++) {
                p = c[i][k];
                q = c[k][k];
                for (int j = 0; j < 3; j++) {
                    if (i != k) {
                        c[i][j] = c[i][j] * q - p * c[k][j];
                        b[i][j] = b[i][j] * q - p * b[k][j];
                    }
                }
            }
        }

        for (int i = 0; i < 3; i++)
            for (int j = 0; j < 3; j++)
                b[i][j] /= c[i][i];

        System.out.println("\nInverse Matrix is: ");
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++)
                System.out.print(b[i][j] + " ");
            System.out.println();
        }
    }
}




PROGRAM: 

import java.io.*; 

import java.util.*; 
import java.io.*; public 
class HillCipher { 
static float[][] decrypt = new float[3][1]; 
static float[][] a = new float[3][3]; static 
float[][] b = new float[3][3]; static 
float[][] mes = new float[3][1]; static 
float[][] res = new float[3][1]; 
static BufferedReader br = new BufferedReader(new 
InputStreamReader(System.in)); static Scanner sc = new Scanner(System.in); 
public static void main(String[] args) throws IOException { 
// TODO code application 
logic here getkeymes(); 
for(int i=0;i<3;i++) for(int j=0;j<1;j++) 
for(int k=0;k<3;k++) { 
res[i][j]=res[i][j]+a[i][k]*mes[k][j]; } 
System.out.print("\nEncrypted string is : 
"); for(int i=0;i<3;i++) { 
System.out.print((char)(res[i][0]%26+97)); 
res[i][0]=res[i][0]; 
} 
inverse(); 
for(int i=0;i<3;i++) 
for(int j=0;j<1;j++) 
for(int k=0;k<3;k++) { 
decrypt[i][j] = decrypt[i][j]+b[i][k]*res[k][j]; } 
System.out.print("\nDecrypted string is : "); 
for(int i=0;i<3;i++){ 
System.out.print((char)(decrypt[i][0]%26+97)); 
} 
System.out.print("\n"); 
} 
public static void getkeymes() throws IOException {
System.out.println("Enter 3x3 matrix for key (It should be inversible): "); 
for(int i=0;i<3;i++) 
for(int j=0;j<3;j++) 
a[i][j] = sc.nextFloat(); 
System.out.print("\nEnter a 3 letter string: "); 
String msg = br.readLine(); 
for(int i=0;i<3;i++) 
mes[i][0] = msg.charAt(i)-97; 
} 
public static void inverse() { 
floatp,q; 
float[][] c = a; 
for(int i=0;i<3;i++) 
for(int j=0;j<3;j++) { 
//a[i][j]=sc.nextFloat(); 
if(i==j) 
b[i][j]=1; 
else b[i][j]=0; 
} 
for(int k=0;k<3;k++) { 
for(int i=0;i<3;i++) { 
p = c[i][k]; 
q = c[k][k]; 
for(int j=0;j<3;j++) { 
if(i!=k) {c[i][j] = c[i][j]*q-p*c[k][j]; 
b[i][j] = b[i][j]*q-p*b[k][j]; 
} } } } 
for(int i=0;i<3;i++) 
for(int j=0;j<3;j++) { 
b[i][j] = b[i][j]/c[i][i]; } 
System.out.println(""); 
System.out.println("\nInverse Matrix is : "); 
for(int i=0;i<3;i++) { 
for(int j=0;j<3;j++) 
System.out.print(b[i][j] + " "); 
System.out.print("\n"); } 
} } 
Output: 
Enter a 3 letter string: hai 
Encrypted string is :fdx 
Inverse Matrix is : 
0.083333336 0.41666666 -0.33333334 
-0.41666666 -0.083333336 0.6666667 
0.5833333 -0.083333336 -0.33333334 
Decrypted string is: hai