FgbHeqWL

1/**
2  _____        _____                  _             
3 |  __ \      / ____|                | |            
4 | |  | | ___| |     _ __ _   _ _ __ | |_ ___  _ __ 
5 | |  | |/ _ \ |    | '__| | | | '_ \| __/ _ \| '__|
6 | |__| |  __/ |____| |  | |_| | |_) | || (_) | |   
7 |_____/ \___|\_____|_|   \__, | .__/ \__\___/|_|   
8                           __/ | |                  
9                          |___/|_|                  
10 */
11class DeCryptor {
12
13    private static final String TRANSFORMATION = "AES/GCM/NoPadding";
14    private static final String ANDROID_KEY_STORE = "AndroidKeyStore";
15
16    private KeyStore keyStore;
17
18    DeCryptor() throws CertificateException, NoSuchAlgorithmException, KeyStoreException,
19            IOException {
20        initKeyStore();
21    }
22
23    private void initKeyStore() throws KeyStoreException, CertificateException,
24            NoSuchAlgorithmException, IOException {
25        keyStore = KeyStore.getInstance(ANDROID_KEY_STORE);
26        keyStore.load(null);
27    }
28
29    String decryptData(final String alias, final byte[] encryptedData, final byte[] encryptionIv)
30            throws UnrecoverableEntryException, NoSuchAlgorithmException, KeyStoreException,
31            NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, IOException,
32            BadPaddingException, IllegalBlockSizeException, InvalidAlgorithmParameterException {
33
34        final Cipher cipher = Cipher.getInstance(TRANSFORMATION);
35        final GCMParameterSpec spec = new GCMParameterSpec(128, encryptionIv);
36        cipher.init(Cipher.DECRYPT_MODE, getSecretKey(alias), spec);
37
38        return new String(cipher.doFinal(encryptedData), "UTF-8");
39    }
40
41    private SecretKey getSecretKey(final String alias) throws NoSuchAlgorithmException,
42            UnrecoverableEntryException, KeyStoreException {
43        return ((KeyStore.SecretKeyEntry) keyStore.getEntry(alias, null)).getSecretKey();
44    }
45}