fUQEYetb

1private static final String PASSWORD = "PASSWORD";
2    private static final String ALGORITHM = "AES";
3    private static final String SECRET_KEY_FACTORY_ALGORITHM = "PBKDF2WithHmacSHA1";
4    private static final String TRANSFORMATION = "AES/CBC/PKCS5Padding";
5    private static final int KEY_LENGTH = 128;
6    private static final int ITERATION = 65536;
7
8    private Cipher encryptCipher;
9    private Cipher decryptCipher;
10    private RandomAccessFile fileToEncrypt;
11    private OutputStream outFile;
12    private byte[] salt;
13    private SecretKey secret;
14    private byte[] iv;
15
16
17    @Override
18    protected Boolean doInBackground(RandomAccessFile... filesFromUser){
19        fileToEncrypt = filesFromUser[0];
20        try {
21
22            outFile =  new FileOutputStream(Folders.EXTERNAL_FOLDER_DIR + "/aFolder/encrypted.des");
23            encryptFile(PASSWORD);
24
25            //TODO below is for testing
26            decryptFile();
27
28
29        } catch (Exception e) {
30            e.printStackTrace();
31        }
32        return true;
33    }
34
35    private void encryptFile(String key) throws Exception {
36
37        this.makeSalt();
38        this.makeSecretKey(key);
39        this.makeCipher();
40        this.makeIV();
41
42        try {
43            byte[] bytesToEncrypt = new byte[(int) fileToEncrypt.length()];
44            fileToEncrypt.read(bytesToEncrypt);
45            byte[] cipheredBytes = encryptCipher.doFinal(bytesToEncrypt);
46            outFile.write(cipheredBytes);
47        }
48        catch (Exception e){
49            Log.i(TAG,e.toString());
50        }
51        finally {
52            fileToEncrypt.close();
53            outFile.close();
54        }
55
56    }
57
58    private void decryptFile() throws Exception {
59
60        this.makeCipherForDecrypt();
61
62
63        RandomAccessFile fileToDecrypt = new RandomAccessFile(Folders.EXTERNAL_FOLDER_DIR + "/aFolder/encrypted.des", "rw");
64        OutputStream outFile  = new FileOutputStream(Folders.EXTERNAL_FOLDER_DIR + "/aFolder/original.jpg");
65        try {
66            byte[] bytesToDecrypt = new byte[(int) fileToDecrypt.length()];
67            fileToDecrypt.read(bytesToDecrypt);
68            byte[] decipheredBytes = decryptCipher.doFinal(bytesToDecrypt);
69            outFile.write(decipheredBytes);
70
71        }catch (Exception e){
72            Log.i(TAG,e.toString());
73
74        }finally {
75            fileToDecrypt.close();
76            outFile.close();
77        }
78
79    }
80
81    private void makeSalt() {
82        salt = new byte[8];
83        SecureRandom secureRandom = new SecureRandom();
84        secureRandom.nextBytes(salt);
85
86    }
87
88    private void makeSecretKey(String key) throws  Exception {
89        SecretKeyFactory factory = SecretKeyFactory.getInstance(SECRET_KEY_FACTORY_ALGORITHM);
90        KeySpec spec = new PBEKeySpec(key.toCharArray(),salt,ITERATION,KEY_LENGTH );
91        SecretKey tmp = factory.generateSecret(spec);
92        secret = new SecretKeySpec(tmp.getEncoded(),ALGORITHM);
93    }
94
95
96    private void makeCipher() throws Exception{
97        encryptCipher = Cipher.getInstance(TRANSFORMATION);
98        encryptCipher.init(Cipher.ENCRYPT_MODE,secret);
99
100    }
101
102
103    private void makeIV()throws Exception{
104        AlgorithmParameters params = encryptCipher.getParameters();
105        iv = params.getParameterSpec(IvParameterSpec.class).getIV();
106    }
107
108    private void makeCipherForDecrypt() throws Exception{
109        decryptCipher = Cipher.getInstance(TRANSFORMATION);
110        decryptCipher.init(Cipher.DECRYPT_MODE,secret, new IvParameterSpec(iv));
111
112    }
113
114}