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1import javax.crypto.BadPaddingException;
2import javax.crypto.IllegalBlockSizeException;
3import java.security.InvalidAlgorithmParameterException;
4import java.security.InvalidKeyException;
5import java.security.NoSuchAlgorithmException; 
6import javax.crypto.NoSuchPaddingException;
7import javax.crypto.SecretKey;
8import javax.crypto.KeyGenerator;
9import javax.crypto.Cipher;
10import javax.crypto.spec.IvParameterSpec;
11
12public class TestSymCypher {
13
14    /**
15     * Test the symmetric cypher on a string
16     * @param the string to cypher
17     */
18    public void testSymCypher(SecretKey k, String str)
19            throws BadPaddingException, IllegalBlockSizeException,
20            InvalidAlgorithmParameterException, InvalidKeyException,
21            NoSuchAlgorithmException, NoSuchPaddingException
22    {
23        Cipher cip = Cipher.getInstance("DES/CBC/PKCS5Padding");
24        cip.init(Cipher.ENCRYPT_MODE,k);
25        byte[] ciphered = cip.doFinal(str.getBytes());
26        byte iv[] = cip.getIV();
27        
28        System.out.println("Original String: " + str);
29        System.out.print("Ciphered: ");
30        printHexadecimal(ciphered);
31        System.out.print("\n");
32        
33        IvParameterSpec dps = new IvParameterSpec(iv);
34        cip.init(Cipher.DECRYPT_MODE,k,dps);
35        byte[] deciphered = cip.doFinal(ciphered);
36        
37        System.out.println("Deciphered String: " + new String(deciphered));
38    }
39    
40    /**
41     * Print a byte array in hexadecimal form
42     * @param the byte array
43     */
44    public void printHexadecimal(byte[] bytes)
45    {
46        for(int i=0; i<bytes.length; i++)
47            System.out.printf("%X",bytes[i]);
48    }
49    
50    public static void main(String args[]) throws Exception 
51    {
52        String stringTest = "How can I believe in God when just last week I " +
53                "got my tongue caught in the roller of an electric typewriter?";
54        
55        TestSymCypher tsc = new TestSymCypher();
56        
57        // Generate a symetric AES secret key
58        KeyGenerator generatorDes = KeyGenerator.getInstance("DES");
59        SecretKey skaes = generatorDes.generateKey();
60        
61        // Cypher and Decypher a string with the AES key
62        tsc.testSymCypher(skaes, stringTest);
63    }
64}