Question

Language is java

Create encryption and decryption that changes char by using ASCII by 5. How to do this using threads?

Let’s assume that our password string is “ABCDEFGHI”, once you run the encrypt function on this string you should get - “FGHIJKLMN” (since you are increasing the ASCII value by 5)

If we call decrypt on this update string right away, it should give us the original string back - “ABCDEFGHI”

Answer 1

import java.util.Scanner;

public class CaesarEncryption {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter your message:");
        String line = in.nextLine();
        System.out.println("\nEnter your shift cipher key:  ");
        int key = in.nextInt();
        char ch;

        String cipher = "";
        for (int i = 0; i < line.length(); i++) {
            ch = line.charAt(i);
            if(Character.isLowerCase(ch)) {
                ch = (char) ('a' + ((ch - 'a' + key + 26) % 26));
            } else if(Character.isUpperCase(ch)) {
                ch = (char) ('A' + ((ch - 'A' + key + 26) % 26));
            }
            cipher += ch;
        }
        System.out.println("\nEncrypted message:\n" + cipher);

        String plain = "";
        for (int i = 0; i < cipher.length(); i++) {
            ch = cipher.charAt(i);
            if(Character.isLowerCase(ch)) {
                ch = (char) ('a' + ((ch - 'a' - key + 26) % 26));
            } else if(Character.isUpperCase(ch)) {
                ch = (char) ('A' + ((ch - 'A' - key + 26) % 26));
            }
            plain += ch;
        }
        System.out.println("\nDecrypted message:\n" + plain);

        in.close();
    }
}