pTegmVJW

1import java.security.Key;
2import java.security.SecureRandom;
3
4import javax.crypto.Cipher;
5import javax.crypto.KeyGenerator;
6import javax.crypto.SecretKey;
7import javax.crypto.spec.IvParameterSpec;
8
9import org.apache.commons.codec.binary.Base64;
10
11public class CryptoHelper {
12
13	public static void main( String [] args ) throws Exception {
14
15		CryptoHelper crypto = new CryptoHelper();
16
17		String plaintext = "This is a good secret.";
18		System.out.println( plaintext );
19
20		String ciphertext = crypto.encrypt( plaintext );
21		System.out.println( ciphertext );
22
23		String decrypted = crypto.decrypt( ciphertext );
24		System.out.println( decrypted );
25
26	}
27
28	public String encrypt( String plaintext ) throws Exception {
29		return encrypt( generateIV(), plaintext );
30	}
31
32	public String encrypt( byte [] iv, String plaintext ) throws Exception {
33
34		byte [] decrypted = plaintext.getBytes();
35		byte [] encrypted = encrypt( iv, decrypted );
36
37		StringBuilder ciphertext = new StringBuilder();
38
39		ciphertext.append( Base64.encodeBase64String( iv ) );
40		ciphertext.append( ":" );
41		ciphertext.append( Base64.encodeBase64String( encrypted ) );
42
43		return ciphertext.toString();
44
45	}
46
47	public String decrypt( String ciphertext ) throws Exception {
48		String [] parts = ciphertext.split( ":" );
49		byte [] iv = Base64.decodeBase64( parts[0] );
50		byte [] encrypted = Base64.decodeBase64( parts[1] );
51		byte [] decrypted = decrypt( iv, encrypted );
52		return new String( decrypted );
53	}
54
55	private Key key;
56
57	public CryptoHelper( Key key ) {
58		this.key = key;
59	}
60
61	public CryptoHelper() throws Exception {
62		this( generateSymmetricKey() );
63	}
64
65	public Key getKey() {
66		return key;
67	}
68
69	public void setKey( Key key ) {
70		this.key = key;
71	}
72
73	public static byte [] generateIV() {
74		SecureRandom random = new SecureRandom();
75		byte [] iv = new byte [16];
76		random.nextBytes( iv );
77		return iv;
78	}
79
80	public static Key generateSymmetricKey() throws Exception {
81		KeyGenerator generator = KeyGenerator.getInstance( "AES" );
82		SecretKey key = generator.generateKey();
83		return key;
84	}
85
86	public byte [] encrypt( byte [] iv, byte [] plaintext ) throws Exception {
87		Cipher cipher = Cipher.getInstance( key.getAlgorithm() + "/CBC/PKCS5Padding" );
88		cipher.init( Cipher.ENCRYPT_MODE, key, new IvParameterSpec( iv ) );
89		return cipher.doFinal( plaintext );
90	}
91
92	public byte [] decrypt( byte [] iv, byte [] ciphertext ) throws Exception {
93		Cipher cipher = Cipher.getInstance( key.getAlgorithm() + "/CBC/PKCS5Padding" );
94		cipher.init( Cipher.DECRYPT_MODE, key, new IvParameterSpec( iv ) );
95		return cipher.doFinal( ciphertext );
96	}
97
98}