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1AES encryption in Java
2package net.sf.andhsli.hotspotlogin;
3
4import java.security.SecureRandom;
5
6import javax.crypto.Cipher;
7import javax.crypto.KeyGenerator;
8import javax.crypto.SecretKey;
9import javax.crypto.spec.SecretKeySpec;
10
11/**
12 * Usage:
13 * <pre>
14 * String crypto = SimpleCrypto.encrypt(masterpassword, cleartext)
15 * ...
16 * String cleartext = SimpleCrypto.decrypt(masterpassword, crypto)
17 * </pre>
18 * @author ferenc.hechler
19 */
20public class SimpleCrypto {
21
22    public static String encrypt(String seed, String cleartext) throws Exception {
23        byte[] rawKey = getRawKey(seed.getBytes());
24        byte[] result = encrypt(rawKey, cleartext.getBytes());
25        return toHex(result);
26    }
27
28    public static String decrypt(String seed, String encrypted) throws Exception {
29        byte[] rawKey = getRawKey(seed.getBytes());
30        byte[] enc = toByte(encrypted);
31        byte[] result = decrypt(rawKey, enc);
32        return new String(result);
33    }
34
35    private static byte[] getRawKey(byte[] seed) throws Exception {
36        KeyGenerator kgen = KeyGenerator.getInstance("AES");
37        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
38        sr.setSeed(seed);
39        kgen.init(128, sr); // 192 and 256 bits may not be available
40        SecretKey skey = kgen.generateKey();
41        byte[] raw = skey.getEncoded();
42        return raw;
43    }
44
45
46    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
47        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
48        Cipher cipher = Cipher.getInstance("AES");
49        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
50        byte[] encrypted = cipher.doFinal(clear);
51        return encrypted;
52    }
53
54    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
55        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
56        Cipher cipher = Cipher.getInstance("AES");
57        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
58        byte[] decrypted = cipher.doFinal(encrypted);
59        return decrypted;
60    }
61
62    public static String toHex(String txt) {
63        return toHex(txt.getBytes());
64    }
65    public static String fromHex(String hex) {
66        return new String(toByte(hex));
67    }
68
69    public static byte[] toByte(String hexString) {
70        int len = hexString.length()/2;
71        byte[] result = new byte[len];
72        for (int i = 0; i < len; i++)
73            result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
74        return result;
75    }
76
77    public static String toHex(byte[] buf) {
78        if (buf == null)
79            return "";
80        StringBuffer result = new StringBuffer(2*buf.length);
81        for (int i = 0; i < buf.length; i++) {
82            appendHex(result, buf[i]);
83        }
84        return result.toString();
85    }
86    private final static String HEX = "0123456789ABCDEF";
87    private static void appendHex(StringBuffer sb, byte b) {
88        sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
89    }
90
91}
92	
93public static void main(String[] args) {
94  try {
95    String plaintext = "Hello world", key = "test";
96    String ciphertext = encrypt(key, plaintext);
97    String plaintext2 = decrypt(key, ciphertext);
98    System.out.println("Encrypting '" + plaintext +
99                       "' yields: (" + ciphertext.length() + ") " + ciphertext);
100    System.out.println("Decrypting it yields: " + plaintext2);
101  }
102  catch (Exception ex) {
103      ex.printStackTrace();
104  }
105}