Simple And Advanced Java Programs

/*************** DES **************
*The program listed below, testDES.java:
takes the DES key input and a text string (to be encrypted) from the program itself (not from a file),

encrypts the string (to produce the ciphertext), writes the key and the ciphertext to a file DES.out, decrypts the ciphertext (still in computer memory), and writes the resulting plaintext string to the file.

In this example, we see see the following three numbers:

DES key: 3812A419C63BE771

Plaintext: 0101010101010101 0102030405060708 090A0B0C0D0E0F10 1112131415161718

Ciphertext: 3A2EAD12F475D82C 1FC97BB9A6D955E1 EA5541946BB4F2E6 F29555A6E8F1FB3C */

import java.io.*;
import java.security.*;
import java.math.*;
import cryptix.util.core.BI;
import cryptix.util.core.ArrayUtil;
import cryptix.util.core.Hex;
import cryptix.provider.key.*;


class testDES {

public static void main (String[] args) {

try {
FileOutputStream outFile1 = new FileOutputStream("DES.out");
// Note: PrintStream is deprecated, but still works fine in jdk1.1.7b
PrintStream output1 = new PrintStream(outFile1);

// convert a string to a DES key and print out the result
RawSecretKey key2 = new RawSecretKey("DES",Hex.fromString("3812A419C63BE771"));
RawKey rkey = (RawKey) key2;
byte[] yval = rkey.getEncoded();
BigInteger Bkey = new BigInteger(yval);
String w = cryptix.util.core.BI.dumpString(Bkey);
output1.println("The Encryption Key = " + w);

// use the DES key to encrypt a string
Cipher des=Cipher.getInstance("DES/ECB/NONE","Cryptix");
des.initEncrypt(key2);
byte[] ciphertext = des.crypt(Hex.fromString("01010101010101010102030405060708090A0B0C0D0E0F101112131415161718"));

// print out length and representation of ciphertext
output1.print("\n");
output1.println("ciphertext.length = " + ciphertext.length);

BigInteger Bciph = new BigInteger(ciphertext);
w = cryptix.util.core.BI.dumpString(Bciph);
output1.println("Ciphertext for DES encryption = " + w);

// decrypt ciphertext
des.initDecrypt(key2);
ciphertext = des.crypt(ciphertext);
output1.print("\n");
output1.println("plaintext.length = " + ciphertext.length);

// print out representation of decrypted ciphertext
Bciph = new BigInteger(ciphertext);
w = cryptix.util.core.BI.dumpString(Bciph);
output1.println("Plaintext for DES encryption = " + w);

output1.println(" ");
output1.close();

} catch (Exception e) {
System.err.println("Caught exception " + e.toString());
}

}}