Question

Hello,

please help me with the follpowing question in java, thank you in advance

Answer 1

please find the java program written below :

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

import java.security.*;

//importing security packages

import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;

public class test {

    static final String ALGORITHM = "AES";             //defining that we will use AES algorithm
    static final String TRANSFORMATION = "AES";

    public static void main (String[] args) {
        InputReader in = new InputReader(System.in);      //creating input reader
        PrintWriter w = new PrintWriter(System.out);     //creating writer

        System.out.println("please enter your name : ");        //taking username as input
        String name = in.nextLine();

        System.out.println("Please enter the input file name : ");
        File inputFile = new File(in.nextLine());

        System.out.println("Enter the password for secret key");       //taking password input for key
        //using make key method for using password as key with some manupulation
        String key = makeKey(in.nextLine());

        File encryptedFile = new File("encrypted.txt");
        File decryptedFile = new File("decrypted.txt");

        encryptWithAES(key, inputFile, encryptedFile);

        decryptWithAES(key, encryptedFile, decryptedFile);

        w.close();
    }
    //defining encrypt method
    public static void encryptWithAES(String key, File inputFile, File outputFile) {

        doCrypto(Cipher.ENCRYPT_MODE, key, inputFile, outputFile);
    }

    //defining decrypt method
    public static void decryptWithAES(String key, File inputFile, File outputFile) {
        doCrypto(Cipher.DECRYPT_MODE, key, inputFile, outputFile);
    }
    //making key from given password
    public static String makeKey(String pass) {
        while (pass.length() < 16) {
            pass += pass;
        }
        return pass.substring(0, 16);

    }
    //function for encryption and decryption
    public static void doCrypto(int cipherMode, String key, File inputFile, File outputFile) {
        try {
            //taking secret key and algorithm to be used
            Key secretKey = new SecretKeySpec(key.getBytes(), ALGORITHM);
            Cipher cipher = Cipher.getInstance(TRANSFORMATION);
            cipher.init(cipherMode, secretKey);

            //getting input file stream
            FileInputStream inputStream = new FileInputStream(inputFile);
            byte[] inputBytes = new byte[(int) inputFile.length()];
            inputStream.read(inputBytes);

            //creating output byte stream
            byte[] outputBytes = cipher.doFinal(inputBytes);

            //creating output file from output byte stream
            FileOutputStream outputStream = new FileOutputStream(outputFile);
            outputStream.write(outputBytes);

            inputStream.close();
            outputStream.close();

        }
        //throwing exception if error occurs
        catch (NoSuchPaddingException | NoSuchAlgorithmException
                    | InvalidKeyException | BadPaddingException
                    | IllegalBlockSizeException | IOException ex) {
            System.out.println("Error encrypting/decrypting file: " + ex);
        }
    }

}

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please find the screenshots of code, its execution along with different input and output files :

Cvavatestjava-Sublime Text (UNREGISTERED) File Edit Selection Find View Goto Tools Praject Help 1544r java static final string ALGORITHM"AES" static final String TRANSFORMATION "AES"; //defining that we will use AES algorithm 12 13 14 15 16 17 18 19 20 21 public static void main (String[] args) InputReader innew InputReader (System.in); Printwriter W new Printhriter(System.out); //creating input reader //creating writer System.out.println("please enter your name: "); string name in.nextLine); //taking username as input System.out.println("Please enter the input file name"); File input File = new File(1n . next Line()); 23 24 25 26 27 28 29 30 31 32 System.out.println("Enter the password for secret key"); //using make key method for using password as key with some manupulatio string key makekey (in.nextline()); //taking password input for key File encryptedFilenew File("encrypted.txt"); File decryptedFile new File("decrypted.txt"); encryptwithAES(key, inputFile, encryptedFile); decryptwithAES(key, encryptedFile, decryptedFile); w.close(); 34 35 36 37 38 39 40 41 42 //defining encrypt method public static void encryptwithAES (String key, File inputFile, File outputFile) ( doCrypto (Cipher.ENCRYPT MODE, key, inputFile, outputFile) Line 2」.CO!mn U1:Sawad L. 2333 O Type here to search %凹 ENG 25-03-2019

Cuavaitestjava- Sublime Text (UNREGISTERED) File Edit Selection Find View Goto Tools Praject Preferences Help 1544r java static final string ALGORITHM"AES" static final String TRANSFORMATION- "AES"; //defining that we will use AES algorithm 12 13 14 15 16 17 18 19 20 21 command Prompt C:java>javac test.java C:java jave test please enter your nane ut alman Please enter the input file nane: yo.txt Enter the pas sword for secret kry C: Njava 23 24 25 26 27 28 29 30 31 32 input for key 34 35 36 37 38 39 40 41 42 w.close(); //defining encrypt method public static void encryptwithAES (String key, File inputFile, File outputFile) ( doCrypto (Cipher.ENCRYPT MODE, key, inputFile, outputFile) Linc 25. Column U 2339 O Type here to search rP ^ D ENG 25-03-2019

Search Tocls yo.txt-Search Results in java Home Shae Search Search Results in java vyo.tt yu.lxt Date medified: 16-03-2019 21:31 C:java Size: 13 bytes Quick access Desitop ya.txt-Notepad Pictures This P File Edit Format View Help bye go hi This PC 3D Cbjects Desktop Music Windows (C:) RECOVERY D) eduation T windows (CRLFL, 1,Col 1 100% 1 item 1 item selected 13 bytes 2340 O Type here to search ENG 25-03-2019

Search Tocls enc-Search Results in java Home Shae Search Search Results in java encrypted.Lxt Quick access Desitop Date medified: ENCMSG.dasSiBzäJm;zqAclo ENCMSGSInpul ENCMSGjava file Edit ora View Help 23-07-201800:35 23-07-2018 00:35 Pictures This P 23-07-2018 00:34 This PC 3D Cbjects Desktop Music Windows (C:) RECOVERY D) eduation T Windows (CRLF Ln 1, Col 1 100% 4 items 1 item selected 16 bytes 2340 O Type here to search ENG 25-03-2019

Search Tocls de Search Results in java Home Shae Search > search Results in Java ˇ File Edit Fomat w Help DecodeClienljava hi bye go hi Windows (CRIF un 1. Col 1 100% ype JNA File 574 bytes Date mcdified: 12-04-2016 00:19 Size 112 KB Type: CLASS File 16 items item selected 13 bytes O Type here to search D ENG 26-03-2019 2340 26-03-2019 5