Question

I’m a German student and for computer classes I need to implement the DES-encryption in Java (by myself, not by using the Java-API) and explain it in detail. I didn’t find any Java-code-examples using google, however I did find an easy implementation in C. (I do not know C, I know a little C++, but not that well, pointer still get me now and then.)

So I tried simply converting the code from C to Java, which did work out about halfway, however I’m having a problem with the last part, especially with the example using:

printf('%c',M); 

Which, from what Google told me, seems to be converting numbers(Integer) to ASCII-Characters, but I’m not really sure. My Code seems to be working until that last part, so I would be thankful for anyone that can give me fix/hint.

My Code:

import java.util.Scanner;  public class DES {      /**      * @param args      */     public static void main(String[] args) {          Scanner eingabe = new Scanner(System.in);          int p, q, key2, fn, encryption_key, temp1 , temp2 ,             t, s =0 , privatekey1=1, b=0 , passwort_s=0, klartext;         int[] Cipher = new int [100];         String passwort;          System.out.println('Enter the value of p and q');          p = eingabe.nextInt();         q = eingabe.nextInt();          System.out.println(p);         System.out.println(q);          key2= p*q;           fn=(p-1)*(q-1);         System.out.println('Enter Enryption key e: ');         encryption_key = eingabe.nextInt();          do {              s=(privatekey1*encryption_key)%fn;             privatekey1++;           } while (s!=1);           privatekey1=privatekey1-1;            System.out.println('Public Key : '+ encryption_key + ','+ key2 );         System.out.println('Private Key: '+ privatekey1 + ',' +key2 );         System.out.println('Enter Message: ');         passwort= eingabe.next();         for ( temp2 = 0; temp2 < passwort.length(); temp2++)          {             t = passwort.charAt(temp2);             passwort_s=1;             for(temp1 =0 ; temp1< encryption_key ; temp1++){                 passwort_s= passwort_s*t%key2;             }             passwort_s= passwort_s%key2;             System.out.println(passwort_s);         }          System.out.println('Enter cipher Text: ');         for(temp1=0;temp1< passwort.length(); temp1++ )         {             Cipher[temp1]= eingabe.nextInt();         }          System.out.println('Plainttext: ');         for(temp2 =0; temp2 < passwort.length(); temp2++);         {             klartext=1;              for(temp1 =0; temp1 < privatekey1; temp1 ++){                 klartext=klartext*Cipher[temp2]%key2;             }             klartext=klartext%key2;             System.out.println(klartext);         }     } } 

How can I convert the

printf('%c',M); 

to Java, and is this then a full DES implementation?

Answer 1

Its late and I’m tired but this isn’t a DES implementation, is it?

It looks more like RSA.

Yeah the link on your post is an asymmetrical cryptosystem. DES is symmetrical.