qK3AzxwF

1import java.security.Key;
2import java.util.Base64;
3
4import javax.crypto.Cipher;
5import javax.crypto.spec.IvParameterSpec;
6import javax.crypto.spec.SecretKeySpec;
7public class StringEnc {
8	private static final String Algorithm = "AES";
9	
10	private static final byte[] keyValue = new byte[] {'S', 'A', 'l', 'L', 'o', 's', 'I', 's', 't', 'O', 'o', 'P', 'f', 'o', 'R', 'u' };
11	
12	public static String AESEncrypt(String Data, int messageNumber) throws Exception {
13
14		Key key = generateKey();		
15		IvParameterSpec ivSpec = createCtrlvForAES(messageNumber);
16		Cipher c = Cipher.getInstance("AES/CTR/PKCS5PADDING");
17		c.init(Cipher.ENCRYPT_MODE, key, ivSpec);		
18		byte[] encVal = c.doFinal(Data.getBytes());
19		byte[] encryptedValue = Base64.getEncoder().encode(encVal);
20		return new String(encryptedValue);
21	}
22	
23	/**
24	 * Generate one SecretKey for Encode and Decode Method.
25	 * 
26	 * @return key (Secret Key)
27	 * @throws Exception
28	 */
29	
30	private static Key generateKey() throws Exception {
31		Key key = new SecretKeySpec(keyValue, Algorithm);
32		return key;
33	}
34	
35
36	public static String AESDecrypt(String encryptedData, int messageNumber) throws Exception {
37		Key key = generateKey();		
38		IvParameterSpec ivSpec = createCtrlvForAES(messageNumber);	
39		Cipher c = Cipher.getInstance("AES/CTR/PKCS5PADDING");		
40		c.init(Cipher.DECRYPT_MODE, key, ivSpec);		
41		byte[] decodedValue = Base64.getDecoder().decode(encryptedData);
42		byte[] decValue = c.doFinal(decodedValue);
43		String decryptedValue = new String(decValue);
44		return decryptedValue;
45	}
46	/**
47	 * @param messageNumber
48	 * @param ivBytes
49	 */
50	
51	public static IvParameterSpec createCtrlvForAES(int messageNumber) {
52		byte[] ivBytes = new byte[16];
53		ivBytes[0] = (byte) (messageNumber >> 32);
54		ivBytes[1] = (byte) (messageNumber >> 24);
55		ivBytes[2] = (byte) (messageNumber >> 16);
56		ivBytes[3] = (byte) (messageNumber >> 8);
57		ivBytes[4] = (byte) (messageNumber >> 0);
58		for (int i = 0; i != 8; i++) {
59			ivBytes[8 + i] = 0;
60		}
61		ivBytes[15] = 1;
62		return new IvParameterSpec(ivBytes);
63 	}
64
65}
66
67
68