offline - 安卓离线播放视频加密

Question

我想从服务器下载 mp4 视频到我的 Android 设备。我希望这个视频以 block (加密)的形式存储，并且应该在视频播放时实时组合。如何着手解决这个问题。

Answer 1

对于这样的样本

public class AESdemo extends Activity {
boolean encryptionIsOn = true;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_aesdemo);
    // needs <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    String homeDirName = Environment.getExternalStorageDirectory().getAbsolutePath() +
            "/" + getPackageName();
    File file = new File(homeDirName, "test.txt");
    byte[] keyBytes = getKey("password");

    try {
        File dir = new File(homeDirName);
        if (!dir.exists())
            dir.mkdirs();
        if (!file.exists())
            file.createNewFile();

        OutputStreamWriter osw;

        if (encryptionIsOn) {
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");
            IvParameterSpec ivParameterSpec = new IvParameterSpec(keyBytes);
            cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);

            FileOutputStream fos = new FileOutputStream(file);
            CipherOutputStream cos = new CipherOutputStream(fos, cipher);
            osw = new OutputStreamWriter(cos, "UTF-8");
        }
        else    // not encryptionIsOn
            osw = new FileWriter(file);

        BufferedWriter out = new BufferedWriter(osw);
        out.write("This is a test\n");
        out.close();
    }
    catch (Exception e) {
        System.out.println("Encryption Exception "+e);
    }

    ///////////////////////////////////
    try {
        InputStreamReader isr;

        if (encryptionIsOn) {
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");
            IvParameterSpec ivParameterSpec = new IvParameterSpec(keyBytes);
            cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);

            FileInputStream fis = new FileInputStream(file);
            CipherInputStream cis = new CipherInputStream(fis, cipher);
            isr = new InputStreamReader(cis, "UTF-8");
        }
        else
            isr = new FileReader(file);

        BufferedReader in = new BufferedReader(isr);
        String line = in.readLine();
        System.out.println("Text read: <"+line+">");
        in.close();
    }
    catch (Exception e) {
        System.out.println("Decryption Exception "+e);
    }
}

private byte[] getKey(String password) throws UnsupportedEncodingException {
    String key = "";
    while (key.length() < 16)
        key += password;
    return key.substring(0, 16).getBytes("UTF-8");
}

使用 .mp4 代替文本文件