A6ywS7Qs

1public class AESHelper {
2
3    public static String encrypt(String seed, String cleartext) throws Exception {
4        byte[] rawKey = getRawKey(seed.getBytes());
5        byte[] result = encrypt(rawKey, cleartext.getBytes());
6        return toHex(result);
7    }
8
9    public static String decrypt(String seed, String encrypted) throws Exception {
10        byte[] rawKey = getRawKey(seed.getBytes());
11        byte[] enc = toByte(encrypted);
12        byte[] result = decrypt(rawKey, enc);
13        return new String(result);
14    }
15
16    private static byte[] getRawKey(byte[] seed) throws Exception {
17        KeyGenerator kgen = KeyGenerator.getInstance("AES");
18        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG","Crypto");
19        sr.setSeed(seed);
20        kgen.init(128, sr); // 192 and 256 bits may not be available
21        SecretKey skey = kgen.generateKey();
22        byte[] raw = skey.getEncoded();
23        return raw;
24    }
25
26
27    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
28        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
29        Cipher cipher = Cipher.getInstance("AES");
30        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
31        byte[] encrypted = cipher.doFinal(clear);
32        return encrypted;
33    }
34
35    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
36        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
37        Cipher cipher = Cipher.getInstance("AES");
38        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
39        byte[] decrypted = cipher.doFinal(encrypted);
40        return decrypted;
41    }
42
43    public static String toHex(String txt) {
44        return toHex(txt.getBytes());
45    }
46    public static String fromHex(String hex) {
47        return new String(toByte(hex));
48    }
49
50    public static byte[] toByte(String hexString) {
51        int len = hexString.length()/2;
52        byte[] result = new byte[len];
53        for (int i = 0; i < len; i++)
54            result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
55        return result;
56    }
57
58    public static String toHex(byte[] buf) {
59        if (buf == null)
60            return "";
61        StringBuffer result = new StringBuffer(2*buf.length);
62        for (int i = 0; i < buf.length; i++) {
63            appendHex(result, buf[i]);
64        }
65        return result.toString();
66    }
67    private final static String HEX = "0123456789ABCDEF";
68    private static void appendHex(StringBuffer sb, byte b) {
69        sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
70    }
71}