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1package com.example.s407330.myapplication;
2
3import javax.crypto.Cipher;
4import javax.crypto.spec.SecretKeySpec;
5
6public class Encrypter {
7
8    private static final String ENCRYPTING_ALGORITHM = "AES/CTR/NoPadding";
9
10    private final KeyGenerator _keyGenerator;
11
12    public Encrypter(KeyGenerator keyGenerator){
13        _keyGenerator = keyGenerator;
14    }
15
16    public String encrypt(String password, String valueToEncrypt) throws Exception {
17
18        // Generate secret key.
19        SecretKeySpec secretKey = _keyGenerator.generateKey(password, ENCRYPTING_ALGORITHM);
20
21        // Initialize cipher.
22        Cipher cipher = Cipher.getInstance(ENCRYPTING_ALGORITHM);
23
24        // Set-up encryption mode with secret key.
25        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
26
27        // Encode string value with particular charset.
28        byte[] byteText = valueToEncrypt.getBytes();
29
30        // Encrypt.
31        byte[] cipherByteText = cipher.doFinal(byteText);
32
33        // Construct new String instance with proper Charset.
34        return new String(cipherByteText);
35    }
36
37    public String decrypt(String password, String encryptedValue) throws Exception {
38
39        // Generate secret key.
40        SecretKeySpec secretKey = _keyGenerator.generateKey(password, ENCRYPTING_ALGORITHM);
41
42        // Initialize cipher.
43        Cipher cipher = Cipher.getInstance(ENCRYPTING_ALGORITHM);
44
45        // Set-up decryption mode with secret key.
46        cipher.init(Cipher.DECRYPT_MODE, secretKey);
47
48        byte[] cipherByteText = encryptedValue.getBytes();
49
50        // Decrypt.
51        byte[] byteText = cipher.doFinal(cipherByteText);
52
53        // Construct new String instance with proper Charset.
54        return new String(byteText);
55    }
56}