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1package com.example.android.secure;
2
3import javax.crypto.Cipher;
4import javax.crypto.SecretKey;
5import javax.crypto.SecretKeyFactory;
6import javax.crypto.spec.IvParameterSpec;
7import javax.crypto.spec.PBEKeySpec;
8import javax.crypto.spec.SecretKeySpec;
9
10public class EncryptionManager {
11
12 // we should get a password from the user
13 String password = "...";
14 String PBE_ALGORITHM = "PBEWithSHA256And256BitAES-CBC-BC";
15 // Important not to rely on default here !!!! use CBC instead of ECB
16 String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding";
17 int NUM_OF_ITERATIONS = 1000;
18 int KEY_SIZE = 256;
19 // generated on first run
20 byte[] salt = "abababababababababa bab".getBytes();
21 byte[] iv = "1234567890abcdef".getBytes();
22 // This is the value to be encrypted.
23 String clearText = "...";
24 byte[] encryptedText;
25 byte[] decryptedText;
26
27 public void exampleCodeNoRealMethod() {
28    try {
29       PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray(), salt, NUM_OF_ITERATIONS, KEY_SIZE);
30       SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(PBE_ALGORITHM);
31       SecretKey tempKey = keyFactory.generateSecret(pbeKeySpec);
32       SecretKey secretKey = new SecretKeySpec(tempKey.getEncoded(), "AES");
33       IvParameterSpec ivSpec = new IvParameterSpec(iv);
34       Cipher encCipher = Cipher.getInstance(CIPHER_ALGORITHM);
35       encCipher.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
36       Cipher decCipher = Cipher.getInstance(CIPHER_ALGORITHM);
37       decCipher.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
38       encryptedText = encCipher.doFinal(clearText.getBytes());
39       decryptedText = decCipher.doFinal(encryptedText);
40       String sameAsClearText = new String(decryptedText);
41    } catch (Exception e) { 
42       // TODO handle this exception
43    }
44 }
45
46} 
47     
48public static SecretKey generateKey(char[] passphraseOrPin, byte[] salt) throws NoSuchAlgorithmException, InvalidKeySpecException {
49    // Number of PBKDF2 hardening rounds to use. Larger values increase
50    // computation time. You should select a value that causes computation
51    // to take >100ms.
52    final int iterations = 1000; 
53
54    // Generate a 256-bit key
55    final int outputKeyLength = 256;
56
57    SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
58    KeySpec keySpec = new PBEKeySpec(passphraseOrPin, salt, iterations, outputKeyLength);
59    SecretKey secretKey = secretKeyFactory.generateSecret(keySpec);
60    return secretKey;
61}