wRG8piaG

1import javax.crypto.*;
2import javax.crypto.spec.GCMParameterSpec;
3import java.nio.ByteBuffer;
4import java.nio.charset.StandardCharsets;
5import java.security.InvalidAlgorithmParameterException;
6import java.security.InvalidKeyException;
7import java.security.NoSuchAlgorithmException;
8import java.util.Base64;
9
10public class AES {
11
12    public String encrypt(String msg, SecretKey key, byte[] iv) {
13
14        byte[] cipher;
15
16        try {
17            Cipher encryptionCipher = Cipher.getInstance("AES/GCM/NoPadding");
18
19            GCMParameterSpec parameterSpec = new GCMParameterSpec(128, iv);
20
21            System.out.format("Key bits: %d\n", key.getEncoded().length * 8);
22            encryptionCipher.init(Cipher.ENCRYPT_MODE, key, parameterSpec);
23
24            byte[] bytes = msg.getBytes();
25
26            cipher = encryptionCipher.doFinal(bytes);
27            ByteBuffer byteBuffer = ByteBuffer.allocate(4 + iv.length + cipher.length);
28            byteBuffer.putInt(iv.length);
29            byteBuffer.put(iv);
30            byteBuffer.put(cipher);
31            cipher = byteBuffer.array();
32            cipher = Base64.getEncoder().encode(cipher);
33
34            return new String(cipher, StandardCharsets.UTF_8);
35        } catch (NoSuchPaddingException | NoSuchAlgorithmException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
36
37            System.out.format("Error: %s\n", e.getMessage());
38            e.printStackTrace();
39        } catch (InvalidAlgorithmParameterException e) {
40            e.printStackTrace();
41        }
42
43        return null;
44    }
45
46    public String decrypt(String cipher, SecretKey key) {
47        byte[] msg;
48
49        try {
50            byte[] bytes = Base64.getDecoder().decode(cipher);
51            ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
52            int ivLength = byteBuffer.getInt();
53            if(ivLength < 12 || ivLength >= 16) { // check input parameter
54                throw new IllegalArgumentException("invalid iv length");
55            }
56            byte[] iv = new byte[ivLength];
57            byteBuffer.get(iv);
58            byte[] cipherText = new byte[byteBuffer.remaining()];
59            byteBuffer.get(cipherText);
60
61
62            Cipher decryptionCipher = Cipher.getInstance("AES/GCM/NoPadding");
63            GCMParameterSpec parameterSpec = new GCMParameterSpec(128, iv);
64            decryptionCipher.init(Cipher.DECRYPT_MODE, key, parameterSpec);
65
66            msg = decryptionCipher.doFinal(cipherText);
67
68            return new String(msg, StandardCharsets.UTF_8);
69        } catch (NoSuchPaddingException | NoSuchAlgorithmException | InvalidKeyException | BadPaddingException | IllegalBlockSizeException | InvalidAlgorithmParameterException e) {
70            e.printStackTrace();
71        }
72
73        return null;
74    }
75}