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1package ffmpegplayer.hb.com.chatlib.utils;
2
3import android.util.Base64;
4import android.util.Log;
5
6import java.io.UnsupportedEncodingException;
7import java.security.GeneralSecurityException;
8import java.security.Key;
9import java.security.NoSuchAlgorithmException;
10import java.security.SecureRandom;
11import java.security.spec.InvalidKeySpecException;
12
13import javax.crypto.Cipher;
14import javax.crypto.SecretKeyFactory;
15import javax.crypto.spec.IvParameterSpec;
16import javax.crypto.spec.PBEKeySpec;
17import javax.crypto.spec.SecretKeySpec;
18
19import ffmpegplayer.hb.com.chatlib.BuildConfig;
20
21/**
22 * Utility class to encrypt / decrypt text.
23 */
24public class AESEncryption {
25    private static final String AES_MODE = "AES/CBC/PKCS5Padding";
26    //    private static final String encryptionKey = "Zp@ss560^)";
27    private static final int ENCRYPTION_KEY_LENGTH = 32;
28    private static final int IV_LENGTH_BYTES = 16;
29    private static final int SALT_LENGTH_BYTES = 8;
30
31    private static SecretKeySpec getSecretKey(byte[] key) throws Exception {
32        return new SecretKeySpec(key, "AES");
33    }
34
35    /**
36     * generate secure random encryption key
37     *
38     * @return
39     */
40    public static String generateAESKey() {
41        String encryptionKey = null;
42        try {
43            encryptionKey = new String(randomBytes(ENCRYPTION_KEY_LENGTH), "UTF8");
44
45            if (BuildConfig.DEBUG) {
46                Log.e("encryptionKey", encryptionKey);
47            }
48
49        } catch (UnsupportedEncodingException e) {
50            e.printStackTrace();
51        } catch (GeneralSecurityException e) {
52            e.printStackTrace();
53        }
54        return encryptionKey;
55    }
56
57    /**
58     * encrypt text
59     *
60     * @param plaintext text to encrypt
61     * @return base64encoded iv:base64 encoded salt:base64 encoded encrypted text
62     */
63    public static String encrypt(String plaintext, String encryptionKey) {
64        try {
65            byte[] input = plaintext.getBytes();
66            byte[] salt = randomBytes(SALT_LENGTH_BYTES);
67            byte[] iv = randomBytes(IV_LENGTH_BYTES);
68
69            byte[] key = deriveKeyFromPassphrase(encryptionKey, salt, 2000);
70
71            Cipher cipher = Cipher.getInstance(AES_MODE);
72            cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(key), new IvParameterSpec(iv));
73                /*
74                 * Now we get back the IV that will actually be used. Some Android
75                 * versions do funny stuff w/ the IV, so this is to work around bugs:
76                 */
77            iv = cipher.getIV();
78
79            Log.e("base 64 encoded iv", Base64.encodeToString(iv, Base64.DEFAULT));
80            byte[] encodedBytes = cipher.doFinal(input);
81            String encryptedBase64Encoded = Base64.encodeToString(encodedBytes, Base64.DEFAULT);
82
83
84            return Base64.encodeToString(iv, Base64.DEFAULT) + ":" + Base64.encodeToString(salt, Base64.DEFAULT) + ":" + encryptedBase64Encoded;
85        } catch (Exception e) {
86            e.printStackTrace();
87        }
88        return null;
89    }
90
91    private static byte[] deriveKeyFromPassphrase(String passphrase, byte[] salt, int iterationCount) throws NoSuchAlgorithmException, InvalidKeySpecException {
92        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
93        PBEKeySpec pbeKeySpec = new PBEKeySpec(passphrase.toCharArray(), salt, iterationCount, 384);
94        Key secretKey = factory.generateSecret(pbeKeySpec);
95        byte[] key = new byte[32];
96        System.arraycopy(secretKey.getEncoded(), 0, key, 0, 32);
97        return key;
98    }
99
100    /**
101     * decrypt encrypted string
102     *
103     * @param encrypted encrypted string. Must be generated by encrypt method.
104     * @return plain text
105     */
106    public static String decrypt(String encrypted, String encryptionKey) {
107        try {
108            String[] splitOfEncrypted = encrypted.split(":");
109            if (splitOfEncrypted.length == 3) {
110                byte[] iv = Base64.decode(splitOfEncrypted[0], Base64.DEFAULT);
111                byte[] salt = Base64.decode(splitOfEncrypted[1], Base64.DEFAULT);
112                byte[] encryptedBytes = Base64.decode(splitOfEncrypted[2], Base64.DEFAULT);
113
114                byte[] key = deriveKeyFromPassphrase(encryptionKey, salt, 2000);
115
116
117                Cipher cipher = Cipher.getInstance(AES_MODE);
118                cipher.init(Cipher.DECRYPT_MODE, getSecretKey(key), new IvParameterSpec(iv));
119                byte[] decodedBytes = cipher.doFinal(encryptedBytes);
120                return new String(decodedBytes);
121            }
122        } catch (Exception e) {
123            e.printStackTrace();
124        }
125        return null;
126    }
127
128    /**
129     * generate secure random bytes
130     *
131     * @param length byte length
132     * @return random bytes
133     * @throws GeneralSecurityException
134     */
135    private static byte[] randomBytes(int length) throws GeneralSecurityException {
136        SecureRandom random = new SecureRandom();
137        byte[] b = new byte[length];
138        random.nextBytes(b);
139        return b;
140    }
141}