Android凭据加密存储区如何使用，java代码示例

Android凭据加密存储区（Credential encrypted storage area）是一种安全存储凭据（如密码、令牌、证书等）的方式，可以保护敏感数据不被恶意应用或攻击者窃取。在使用Credential encrypted storage area时，需要创建一个Key，用于加密和解密数据。以下是一个简单的Java代码示例，演示如何使用Credential encrypted storage area：

1. 创建一个Key

Key key = null;
KeyguardManager keyguardManager = (KeyguardManager) getSystemService(Context.KEYGUARD_SERVICE);
if (keyguardManager.isKeyguardSecure()) {
    // Create the keys for Credential Encrypted Storage Area
    KeyGenParameterSpec.Builder builder = new KeyGenParameterSpec.Builder(
            "myKeyAlias",
            KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)
            .setBlockModes(KeyProperties.BLOCK_MODE_GCM)
            .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
            .setKeySize(256)
            .setUserAuthenticationRequired(true)
            .setUserAuthenticationValidityDurationSeconds(30);
    KeyGenerator keyGenerator = KeyGenerator.getInstance(
            KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore");
    keyGenerator.init(builder.build());
    key = keyGenerator.generateKey();
}

2. 存储数据

String dataToStore = "my password";
byte[] encryptedData = null;
try {
    // Get the Cipher
    Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
    cipher.init(Cipher.ENCRYPT_MODE, key);
    // Encrypt the data
    encryptedData = cipher.doFinal(dataToStore.getBytes());
} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
    e.printStackTrace();
}

if (encryptedData != null) {
    // Store the encrypted data in the SharedPreferences
    SharedPreferences.Editor editor = getSharedPreferences("myPrefs", MODE_PRIVATE).edit();
    editor.putString("myEncryptedData", Base64.encodeToString(encryptedData, Base64.DEFAULT));
    editor.apply();
}

3. 读取数据

String encryptedDataString = getSharedPreferences("myPrefs", MODE_PRIVATE)
        .getString("myEncryptedData", null);
if (encryptedDataString != null) {
    byte[] encryptedData = Base64.decode(encryptedDataString, Base64.DEFAULT);
    try {
        // Get the Cipher
        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
        cipher.init(Cipher.DECRYPT_MODE, key);
        // Decrypt the data
        byte[] decryptedData = cipher.doFinal(encryptedData);
        String data = new String(decryptedData);
        Log.d(TAG, "Decrypted data: " + data);
    } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
        e.printStackTrace();
    }
}

以上是一个简单的示例，更复杂的应用可能需要更多的代码来管理Key和加密/解密数据。同时，需要注意，Credential encrypted storage area只能在设备上启用了屏幕锁定并设置了密码、PIN码、图案等屏幕锁定方式时才能使用。