43 | * Created by woxingxiao on 2017-09-01.
44 | */
45 |
46 | public class EncryptHelper {
47 |
48 | private static final String KEYSTORE_PROVIDER = "AndroidKeyStore";
49 | private static final String AES_MODE = "AES/GCM/NoPadding";
50 | private static final String RSA_MODE = "RSA/ECB/PKCS1Padding";
51 |
52 | private static final String KEY_IV = "security_key_iv";
53 | private static final String KEY_AES_KEY = "security_key_aes_key";
54 |
55 | private KeyStore mKeyStore;
56 | private String mAlias;
57 | private SharedPreferences mSharedPreferences;
58 |
59 | @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN_MR2)
60 | public EncryptHelper(@NonNull Context context) {
61 | try {
62 | mKeyStore = KeyStore.getInstance(KEYSTORE_PROVIDER);
63 | mKeyStore.load(null);
64 |
65 | mAlias = context.getPackageName();
66 | mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
67 |
68 | if (!mKeyStore.containsAlias(mAlias)) {
69 | mSharedPreferences.edit().putString(KEY_IV, "").apply();
70 | genKeyStoreKey(context);
71 | genAESKey();
72 | }
73 | } catch (Exception e) {
74 | e.printStackTrace();
75 | }
76 | }
77 |
78 | private void genKeyStoreKey(Context context) throws Exception {
79 | if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
80 | generateRSAKeyApi23();
81 | } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
82 | generateRSAKeApi18(context);
83 | }
84 | }
85 |
86 | @RequiresApi(api = Build.VERSION_CODES.M)
87 | private void generateRSAKeyApi23() throws NoSuchAlgorithmException, NoSuchProviderException,
88 | InvalidAlgorithmParameterException {
89 |
90 | KeyPairGenerator keyPairGenerator = KeyPairGenerator
91 | .getInstance(KeyProperties.KEY_ALGORITHM_RSA, KEYSTORE_PROVIDER);
92 |
93 | KeyGenParameterSpec keyGenParameterSpec = new KeyGenParameterSpec
94 | .Builder(mAlias, KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
95 | .setDigests(KeyProperties.DIGEST_SHA256, KeyProperties.DIGEST_SHA512)
96 | .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_RSA_PKCS1)
97 | .build();
98 |
99 | keyPairGenerator.initialize(keyGenParameterSpec);
100 | keyPairGenerator.generateKeyPair();
101 | }
102 |
103 | @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN_MR2)
104 | private void generateRSAKeApi18(Context context) throws NoSuchAlgorithmException, NoSuchProviderException,
105 | InvalidAlgorithmParameterException {
106 |
107 | Calendar start = Calendar.getInstance();
108 | Calendar end = Calendar.getInstance();
109 | end.add(Calendar.YEAR, 30);
110 | KeyPairGeneratorSpec spec = new KeyPairGeneratorSpec.Builder(context)
111 | .setAlias(mAlias)
112 | .setSubject(new X500Principal("CN=" + mAlias))
113 | .setSerialNumber(BigInteger.TEN)
114 | .setStartDate(start.getTime())
115 | .setEndDate(end.getTime())
116 | .build();
117 |
118 | KeyPairGenerator keyPairGenerator = KeyPairGenerator
119 | .getInstance(KeyProperties.KEY_ALGORITHM_RSA, KEYSTORE_PROVIDER);
120 |
121 | keyPairGenerator.initialize(spec);
122 | keyPairGenerator.generateKeyPair();
123 | }
124 |
125 | private void genAESKey() throws Exception {
126 | // Generate AES-Key
127 | byte[] aesKey = new byte[16];
128 | SecureRandom secureRandom = new SecureRandom();
129 | secureRandom.nextBytes(aesKey);
130 |
131 | // Generate 12 bytes iv then save to SharedPrefs
132 | byte[] generated = secureRandom.generateSeed(12);
133 | String iv = Base64.encodeToString(generated, Base64.DEFAULT);
134 | mSharedPreferences.edit().putString(KEY_IV, iv).apply();
135 |
136 | // Encrypt AES-Key with RSA Public Key then save to SharedPrefs
137 | String encryptAESKey = encryptRSA(aesKey);
138 | mSharedPreferences.edit().putString(KEY_AES_KEY, encryptAESKey).apply();
139 | }
140 |
141 | private String encryptRSA(byte[] plainText) throws Exception {
142 | PublicKey publicKey = mKeyStore.getCertificate(mAlias).getPublicKey();
143 |
144 | Cipher cipher = Cipher.getInstance(RSA_MODE);
145 | cipher.init(Cipher.ENCRYPT_MODE, publicKey);
146 |
147 | byte[] encryptedByte = cipher.doFinal(plainText);
148 | return Base64.encodeToString(encryptedByte, Base64.DEFAULT);
149 | }
150 |
151 | private byte[] decryptRSA(String encryptedText) throws Exception {
152 | PrivateKey privateKey = (PrivateKey) mKeyStore.getKey(mAlias, null);
153 |
154 | Cipher cipher = Cipher.getInstance(RSA_MODE);
155 | cipher.init(Cipher.DECRYPT_MODE, privateKey);
156 |
157 | byte[] encryptedBytes = Base64.decode(encryptedText, Base64.DEFAULT);
158 | return cipher.doFinal(encryptedBytes);
159 | }
160 |
161 | /**
162 | * Encryption.
163 | *
164 | * @param plainText The plain text you want to encrypted.
165 | * @return The encrypted text.
166 | * @throws Exception NoSuchAlgorithmException, NoSuchProviderException, InvalidAlgorithmParameterException.
167 | */
168 | public String encrypt(String plainText) throws Exception {
169 | return encryptAES(plainText);
170 | }
171 |
172 | /**
173 | * Decryption.
174 | *
175 | * @param encryptedText The encrypted text you want to decrypted.
176 | * @return The decrypted text.
177 | * @throws Exception NoSuchAlgorithmException, NoSuchProviderException, InvalidAlgorithmParameterException.
178 | */
179 | public String decrypt(String encryptedText) throws Exception {
180 | return decryptAES(encryptedText);
181 | }
182 |
183 | private String encryptAES(String plainText) throws Exception {
184 | Cipher cipher = Cipher.getInstance(AES_MODE);
185 | cipher.init(Cipher.ENCRYPT_MODE, getAESKey(), new IvParameterSpec(getIV()));
186 |
187 | byte[] encryptedBytes = cipher.doFinal(plainText.getBytes());
188 | return Base64.encodeToString(encryptedBytes, Base64.DEFAULT);
189 | }
190 |
191 | private String decryptAES(String encryptedText) throws Exception {
192 | byte[] decodedBytes = Base64.decode(encryptedText.getBytes(), Base64.DEFAULT);
193 | Cipher cipher = Cipher.getInstance(AES_MODE);
194 | cipher.init(Cipher.DECRYPT_MODE, getAESKey(), new IvParameterSpec(getIV()));
195 |
196 | return new String(cipher.doFinal(decodedBytes));
197 | }
198 |
199 | private SecretKeySpec getAESKey() throws Exception {
200 | String encryptedKey = mSharedPreferences.getString(KEY_AES_KEY, "");
201 | byte[] aesKey = decryptRSA(encryptedKey);
202 |
203 | return new SecretKeySpec(aesKey, AES_MODE);
204 | }
205 |
206 | private byte[] getIV() {
207 | String prefIV = mSharedPreferences.getString(KEY_IV, "");
208 | return Base64.decode(prefIV, Base64.DEFAULT);
209 | }
210 | }
211 |
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