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1package uk.tommyt.kafka.krypto;
2
3import org.bouncycastle.jce.provider.BouncyCastleProvider;
4
5import javax.crypto.BadPaddingException;
6import javax.crypto.Cipher;
7import javax.crypto.IllegalBlockSizeException;
8import javax.crypto.KeyGenerator;
9import javax.crypto.NoSuchPaddingException;
10import javax.crypto.SecretKey;
11import javax.crypto.spec.IvParameterSpec;
12import javax.crypto.spec.SecretKeySpec;
13import java.security.InvalidAlgorithmParameterException;
14import java.security.InvalidKeyException;
15import java.security.NoSuchAlgorithmException;
16import java.security.SecureRandom;
17import java.security.Security;
18
19public class AesUniqueIv {
20    private static final String CIPHER = "AES/GCM/NoPadding";
21    private static final String KEY_TYPE = "AES";
22    private static final int AES_BITS = 256;
23    private static final int IV_BYTES = 16;
24    private final SecureRandom secureRandom = new SecureRandom();
25    private SecretKey secretKey;
26    private Cipher cipher;
27
28    static {
29        Security.addProvider(new BouncyCastleProvider());
30    }
31
32    /**
33     * Encryptor with random key
34     */
35    public AesUniqueIv() throws NoSuchAlgorithmException, NoSuchPaddingException {
36        this(newKey());
37    }
38
39    /**
40     * Encryptor with provided key
41     */
42    public AesUniqueIv(byte[] key) throws NoSuchAlgorithmException, NoSuchPaddingException {
43        this(new SecretKeySpec(key, KEY_TYPE));
44    }
45
46    private AesUniqueIv(SecretKey key) throws NoSuchPaddingException, NoSuchAlgorithmException {
47        this.secretKey = key;
48        cipher = Cipher.getInstance(CIPHER);
49    }
50
51    public byte[] getKey() {
52        return secretKey.getEncoded();
53    }
54
55    public byte[] encrypt(byte[] message) throws InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {
56        IvParameterSpec iv = newIvParameterSpec();
57        cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);
58        byte[] encrypted = cipher.doFinal(message);
59        byte[] encryptedWithIv = new byte[IV_BYTES + encrypted.length];
60        System.arraycopy(iv.getIV(), 0, encryptedWithIv, 0, iv.getIV().length);
61        System.arraycopy(encrypted, 0, encryptedWithIv, IV_BYTES, encrypted.length);
62        return encryptedWithIv;
63    }
64
65    public byte[] decrypt(byte[] message) throws InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {
66        byte[] iv = new byte[IV_BYTES];
67        byte[] encrypted = new byte[message.length - IV_BYTES];
68        System.arraycopy(message, 0, iv, 0, IV_BYTES);
69        System.arraycopy(message, IV_BYTES, encrypted, 0, message.length - IV_BYTES);
70        cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
71        return cipher.doFinal(encrypted);
72    }
73
74    private static SecretKey newKey() throws NoSuchAlgorithmException {
75        KeyGenerator keyGenerator = KeyGenerator.getInstance(KEY_TYPE);
76        keyGenerator.init(AES_BITS);
77        return keyGenerator.generateKey();
78    }
79
80    private IvParameterSpec newIvParameterSpec() {
81        byte[] iv = new byte[IV_BYTES];
82        secureRandom.nextBytes(iv);
83        return new IvParameterSpec(iv);
84    }
85}