加密和解密文件

Question

我需要下载 mp3 文件，必要时加密，以解密临时 mp3 并收听。

用作参考这个答案已经在 StackOverflow 中完成

Encrypting files with AES on Android

所有步骤都有效。但是当我为 MediaPlayer 发送生成的 mp3 文件时无法识别和中断。

这些是我的下载和加密方法

 public void executeAsyncDownload(String urlFile, String id, int position, HandlerCallback callback) {

    String encryptedName = Cypher.md5(id);

    if (MediaUtils.containsFile(encryptedName)) {
        callback.onDownloadFinish(position);
        return;
    }

    File dir = MediaUtils.getDestinationFolder(destination);

    if (!dir.exists()) {
        dir.mkdir();
    }

    try {
        if (canceled)
            return;

        callback.onDownloadStart(position);
        URL url = new URL(urlFile);
        URLConnection connection = url.openConnection();
        connection.connect();
        int tamFile = connection.getContentLength();
        String filePath = MediaUtils.getFilePath(MediaUtils.tempPath + encryptedName).toString();

        InputStream fis = new BufferedInputStream(url.openStream());
        OutputStream fos = new FileOutputStream(filePath);
        File file = new File(filePath);

        byte data[] = new byte[80192];
        int count;
        long total = 0;

        while ((count = fis.read(data)) != -1) {
            total += count;
            if (tamFile > 0) {
                int percentage = (int) (total * 100 / tamFile);
                if (percentage % 20 == 0)
                    callback.onDownloadProgress(percentage, position);
            }

            fos.write(data, 0, count);

            if (canceled) {
                MediaUtils.deleteFile(file);
                return;
            }
        }


        if (canceled)
            return;


        byte[] key = (salt + cryptPassword).getBytes("UTF-8");
        MessageDigest sha = MessageDigest.getInstance("SHA-1");
        key = sha.digest(key);
        key = Arrays.copyOf(key, 8);
        SecretKeySpec sks = new SecretKeySpec(key, "DES");
        Cipher cipher = Cipher.getInstance("DES/ECB/NoPadding");
        cipher.init(Cipher.ENCRYPT_MODE, sks);
        CipherOutputStream cos = new CipherOutputStream(fos, cipher);

        int b;
        byte[] d = new byte[8192];
        while ((b = fis.read(d)) != -1) {
            cos.write(d, 0, b);
        }

        OutputStream outputEncrypted = new FileOutputStream(dir + File.separator + encryptedName);
        outputEncrypted.write(d);
        outputEncrypted.close();


        fos.flush();
        fos.close();
        fis.close();

        MediaUtils.deleteFile(file);//delete temp file

        callback.onDownloadFinish(position);
    } catch (Exception e) {
        e.printStackTrace();
        callback.onDownloadError(position);
    }
}

这是我的解密方法

 @SafeVarargs
@Override
protected final File doInBackground(HashMap<String, Object>... params) {
    String path = (String) params[0].get(FILE_PATH);
    String fileName = String.valueOf(params[0].get(FILE_NAME));
    boolean encrypted = (boolean) params[0].get(ENCRYPTED);

    File root = android.os.Environment.getExternalStorageDirectory();
    File dir = new File(root.getAbsolutePath() + File.separator + path + File.separator);
    File file;

    if (!encrypted) {
        file = new File(dir + File.separator + fileName);
        return file;
    }

    file = new File(dir + File.separator + Cypher.md5(fileName));
    File tempMp3 = null;
    try {
        tempMp3 = File.createTempFile(TEMP, MP3, context.getCacheDir());
        tempMp3.deleteOnExit();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        FileInputStream fis = new FileInputStream(file);
        byte[] key = (DownloadManager.salt + DownloadManager.cryptPassword).getBytes("UTF-8");
        MessageDigest sha = MessageDigest.getInstance("SHA-1");
        key = sha.digest(key);
        key = Arrays.copyOf(key, 8);
        SecretKeySpec sks = new SecretKeySpec(key, "DES");
        Cipher cipher = Cipher.getInstance("DES/ECB/NoPadding");
        cipher.init(Cipher.DECRYPT_MODE, sks);
        CipherInputStream cis = new CipherInputStream(fis, cipher);

        FileOutputStream fos = new FileOutputStream(tempMp3);

        int b;
        byte[] d = new byte[80192];
        while ((b = cis.read(d)) != -1) {
            fos.write(d, 0, b);
        }

        fos.flush();
        fos.close();
        cis.close();

    } catch (IOException e) {
        e.printStackTrace();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        e.printStackTrace();
    }

    return tempMp3;
}

Answer 1

您的加密或解密方法似乎有错字。

在加密中：

    int b;
    byte[] d = new byte[8192];
    while ((b = cis.read(d)) != -1) {
        fos.write(d, 0, b);
    }

在解密中：

    int b;
    byte[] d = new byte[80192];
    while ((b = cis.read(d)) != -1) {
        fos.write(d, 0, b);
    }

解密时的字节数组 d 比加密时的字节数组大 10 倍左右。

Answer 2

这样做之后：

    CipherOutputStream cos = new CipherOutputStream(fos, cipher);

    int b;
    byte[] d = new byte[8192];
    while ((b = fis.read(d)) != -1) {
        cos.write(d, 0, b);
    }

    OutputStream outputEncrypted = new FileOutputStream(dir + File.separator + encryptedName);
    outputEncrypted.write(d);
    outputEncrypted.close();

outputEncrypted 文件将只包含最后一个充满数据的缓冲区。此外，这些数据不会被加密。