k9fqt4C6

1public class ECC {
2
3    public static byte[] iv = new SecureRandom().generateSeed(16);
4
5
6    public static KeyPair generateECKeys() throws NoSuchProviderException, NoSuchAlgorithmException, InvalidAlgorithmParameterException {
7
8        ECGenParameterSpec ecParamSpec = new ECGenParameterSpec("prime256v1");
9        KeyPairGenerator kpg = KeyPairGenerator.getInstance("ECDH", "SC");
10        kpg.initialize(ecParamSpec);
11        return kpg.generateKeyPair();
12    }
13
14    public static SecretKey generateSharedSecret(PrivateKey privateKey,
15                                                 PublicKey publicKey) {
16        try {
17            KeyAgreement keyAgreement = KeyAgreement.getInstance("ECDH", "SC");
18            keyAgreement.init(privateKey);
19            keyAgreement.doPhase(publicKey, true);
20
21            SecretKey key = keyAgreement.generateSecret("AES");
22            return key;
23        } catch (InvalidKeyException | NoSuchAlgorithmException
24                | NoSuchProviderException e) {
25      
26            e.printStackTrace();
27            return null;
28        }
29    }
30
31    public static String encryptString(SecretKey key, String plainText) {
32        try {
33
34
35            IvParameterSpec ivSpec = new IvParameterSpec(iv);
36
37            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7PADDING","SC");
38
39            cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
40            byte[] encrypted = cipher.doFinal(plainText.getBytes());
41
42            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
43            outputStream.write(ivSpec.getIV());
44            outputStream.write(encrypted);
45
46            return bytesToHex(outputStream.toByteArray());
47
48
49        } catch (NoSuchAlgorithmException | NoSuchProviderException
50                | NoSuchPaddingException | InvalidKeyException
51                | UnsupportedEncodingException
52                | IllegalBlockSizeException | BadPaddingException e) {
53            e.printStackTrace();
54            return null;
55        } catch (InvalidAlgorithmParameterException e) {
56            e.printStackTrace();
57            return null;
58        } catch (IOException e) {
59            e.printStackTrace();
60            return null;
61        }
62    }
63
64
65    public static String bytesToHex(byte[] data, int length) {
66        String digits = "0123456789ABCDEF";
67        StringBuffer buffer = new StringBuffer();
68
69        for (int i = 0; i != length; i++) {
70            int v = data[i] & 0xff;
71
72            buffer.append(digits.charAt(v >> 4));
73            buffer.append(digits.charAt(v & 0xf));
74        }
75
76        return buffer.toString();
77    }
78
79    public static String bytesToHex(byte[] data) {
80        return bytesToHex(data, data.length);
81    }
82
83    public static byte[] hexToBytes(String string) {
84        int length = string.length();
85        byte[] data = new byte[length / 2];
86        for (int i = 0; i < length; i += 2) {
87            data[i / 2] = (byte) ((Character.digit(string.charAt(i), 16) << 4) + Character
88                    .digit(string.charAt(i + 1), 16));
89        }
90        return data;
91    }
92
93
94    public static PublicKey loadPublicKey (byte [] data) throws Exception
95    {
96
97        ECParameterSpec params = ECNamedCurveTable.getParameterSpec("prime256v1");
98        ECPublicKeySpec pubKey = new ECPublicKeySpec(
99                params.getCurve().decodePoint(data), params);
100        KeyFactory kf = KeyFactory.getInstance("ECDH", "SC");
101        return kf.generatePublic(pubKey);
102    }
103}