在Android中保护用户的应用内部文件夹 [英] Protect app internal folder from users in android

问题描述

如何通过限制用户打开应用程序内部文件夹中的数据来提供安全性，即使设备已经生根，
我遇到AES加密的一种方法，但我想知道是他们的方式，我们可以这样做到一个文件夹，或者我们可以创建一个文件，我们可以在其中访问已下载的必要图像或pdf，并且与最终用户保持距离。

How to provide security to data which were stored in app internal folder by restricting user to open it even if the device is rooted, One method i have encountered AES Encryption but i want to know is their way we can do this to a folder or can we create a file in which we can access necessary image or pdf which were downloaded and stay far reach from end user.

推荐答案

对于加密

public void encryptFile(View v) {
    Bitmap bitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory() + "/img.png");
    // Write image data to ByteArrayOutputStream
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);


    // Encrypt and save the image
    saveFile(encrypt(key, baos.toByteArray()), "enimg.png");
    Toast.makeText(getApplicationContext(), "The image is encrypted", Toast.LENGTH_LONG).show();

    image.setImageURI(Uri.parse(Environment.getExternalStorageDirectory() + "enimg.png"));

}

private byte[] encrypt(byte[] skey, byte[] data) {
    SecretKeySpec skeySpec = new SecretKeySpec(skey, "AES");
    Cipher cipher;
    byte[] encrypted = null;
    try {
        // Get Cipher instance for AES algorithm
        cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        // Initialize cipher
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(iv));
        // Encrypt the image byte data
        encrypted = cipher.doFinal(data);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return encrypted;
}

解密

public void decryptFile(View v) {
    try {
        // Create FileInputStream to read from the encrypted image file
        FileInputStream fis = new FileInputStream(Environment.getExternalStorageDirectory() + "/enimg.png");

        // Save the decrypted image
        saveFile(decrypt(key, fis), "deimg.png");

        Toast.makeText(getApplicationContext(), "The image is decrypted", Toast.LENGTH_LONG).show();

        image.setImageURI(Uri.parse(Environment.getExternalStorageDirectory() + "/deimg.png"));
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

private byte[] decrypt(byte[] skey, FileInputStream fis) {
    SecretKeySpec skeySpec = new SecretKeySpec(skey, "AES");
    Cipher cipher;
    byte[] decryptedData = null;
    CipherInputStream cis = null;
    try {
        cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(iv));
        // Create CipherInputStream to read and decrypt the image data
        cis = new CipherInputStream(fis, cipher);
        // Write encrypted image data to ByteArrayOutputStream
        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
        byte[] data = new byte[2048];
        while ((cis.read(data)) != -1) {
            buffer.write(data);
        }
        buffer.flush();
        decryptedData = buffer.toByteArray();


    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            fis.close();
            cis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    return decryptedData;
}

将这些文件保存在某个位置

To save these file at a location

public void saveFile(byte[] data, String outFileName) {
    FileOutputStream fos = null;
    try {
        fos = new FileOutputStream(Environment.getExternalStorageDirectory() + File.separator + outFileName);
        fos.write(data);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally {
        try {
            fos.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

密钥用于加密并解密声明全局 //获取密钥
key = getKey（）;
// Get IV
iv = getIV（）;

the key is made to encrypt and decrypt declare it global // Get key key = getKey(); // Get IV iv = getIV();

private static byte[] getKey() {
    KeyGenerator keyGen;
    byte[] dataKey = null;
    try {
        // Generate 256-bit key
        keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(256);
        SecretKey secretKey = keyGen.generateKey();
        dataKey = secretKey.getEncoded();
    } catch (NoSuchAlgorithmException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return dataKey;

}

对于加密jst需要调用函数 encryptFile 和 decryptFile 进行解密

For encryption jst need to call the function encryptFile and decryptFile for decryption

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