当Decrypting Image时,给出了javax.crypto.BadPaddingException:pad块损坏的Android

Question

嗨,我是Android和图像加密的新手.我的情况是这样的,

• 首先,我正在加密图像文件.
• 然后我将它上传到服务器
• 从我的应用程序我下载加密图像并将其保存在SD卡中.
• 然后我在将它设置为imageView之前解密它

(请参阅我已经使用的所有需要​​方法的底部..)

但是我得到了javax.crypto.BadPaddingException:解密时pad块被破坏了.我读了一些关于这个例外的文章,但都是关于文本加密的.你能帮我避免这个吗？先感谢您

Image Encrption使用...

private byte[] encrypt(byte[] raw, byte[] clear) throws Exception
{
    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
    byte[] encrypted = cipher.doFinal(clear);
    return encrypted;
}

在这里我也保存了其他几张图片,所有图像都成功保存在SD卡中...

for (int i = 0; i < imageUrls.size(); i++)
                {
                    File file = new File(imageUrls.get(i));

                    String metapath = CommonUtils.getDataFromPreferences("metaPath", "");
                    Log.d("metapath", metapath);
                    String extStorageDirectory = metapath + file.getName();

                    File wallpaperDirectory = new File(extStorageDirectory);
                    if (!wallpaperDirectory.exists() || wallpaperDirectory.length() == 0)
                    {
                        new DownloadImagesTask()
                            .executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, imageUrls.get(i));
                    }
                }
                Toast toast = Toast.makeText(ScratchDetailsActivity.this, "Lottery was purchased and saved to sdcard/E-Lottery",
                    Toast.LENGTH_LONG);
                toast.setGravity(Gravity.CENTER, 0, 0);
                toast.show();

图像解密......

在这里解密文件第一个参数是密钥,第二个是从SD卡获得的加密文件.

        decrpt = simpleCrypto.decrypt(KEY, getImageFileFromSdCard());
        bmpimg2 = BitmapFactory.decodeByteArray(decrpt, 0, decrpt.length);
        Drawable d = new BitmapDrawable(getResources(), bmpimg2);
        hiddenImage.setImageDrawable(d);

DownloadImageTask ..

public class DownloadImagesTask extends AsyncTask<String, Void, InputStream>{
private String fileName;

@Override
protected InputStream doInBackground(String... urls)
{
    //Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
    return download_Image(urls[0]);
}

@Override
protected void onPostExecute(InputStream result)
{
    storeImage(result);

}

private InputStream download_Image(String url)
{
    InputStream is = null;
    File file = new File(url);
    fileName = file.getName();
    try
    {
        URL aURL = new URL(url);
        URLConnection conn = aURL.openConnection();
        conn.connect();
        is = conn.getInputStream();
    }
    catch (OutOfMemoryError e)
    {
        Log.e("Hub", "Error getting the image from server : " + e.getMessage().toString());
    }
    catch (IOException e)
    {
        Log.e("Hub", "Error getting the image from server : " + e.getMessage().toString());
    }

    return is;
}

public void storeImage(InputStream is)
{

    String extStorageDirectory = CommonUtils.getDataFromPreferences("metaPath", "");

    Log.d("extStorageDirectory", extStorageDirectory);
    OutputStream outStream = null;

    File wallpaperDirectory = new File(extStorageDirectory);
    if (!wallpaperDirectory.exists())
    {
        wallpaperDirectory.mkdirs();
    }
    File outputFile = new File(wallpaperDirectory, fileName);
    if (!outputFile.exists() || outputFile.length() == 0)
    {
        try
        {
            outStream = new FileOutputStream(outputFile);
        }
        catch (FileNotFoundException e1)
        {
            e1.printStackTrace();
        }

        try
        {
            int bytesRead = -1;
            byte[] buffer = new byte[4096];
            while ((bytesRead = is.read(buffer)) != -1)
            {
                outStream.write(buffer, 0, bytesRead);
            }

            outStream.close();
            is.close();
            Log.d("ScratchActivtiy", "Image Saved");

        }
        catch (FileNotFoundException e)
        {
            e.printStackTrace();

        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}}

getImageFileFromSDCard方法

/**
     * This method fetch encrypted file which is save in sd card and convert it in byte array after that this file will
     * be decrept.
     * 
     * @return byte array of encrypted data for decription.
     * @throws FileNotFoundException
     */

public byte[] getImageFileFromSdCard() throws FileNotFoundException
{

    byte[] inarry = null;

    try
    {
        String metapath = CommonUtils.getDataFromPreferences("metaPath", "");

        File imageFolder = new File(metapath);
        File urlFile = new File(selectedLottery.getImage());

        for (File f : imageFolder.listFiles())
        {
            if (urlFile.getName().equals(f.getName()))
                metapath = metapath + f.getName();
        }
        File imageFile = new File(metapath);
        //Convert file into array of bytes.
        FileInputStream fileInputStream = null;
        byte[] bFile = new byte[(int) imageFile.length()];
        fileInputStream = new FileInputStream(imageFile);
        fileInputStream.read(bFile);
        fileInputStream.close();
        inarry = bFile;

    }
    catch (IOException e)
    {
        Log.d("Exception", e.getMessage());
    }

    return inarry;
}

Answer 1

有很多事情可能导致Bad Padding异常.要检查的明显事项是您正在使用的加密和解密:

1. 相同的密钥,即逐字节相同.

2. 相同的加密模式(通常为CBC,CTR或GCM).

3. 相同的IV/Nonce,再次逐字节相同.

4. 相同的填充(PKCS5或PKCS7是常见的).

不要依赖系统默认值,尤其是在一个系统上加密并在另一个系统上进行解密时,就像您似乎正在做的那样.如果系统默认值不同,则解密将失败.始终明确设置键,模式,IV和填充.在任何合理的加密库中都会有记录的方法.

如果这没有解决它,那么你将需要做更多的挖掘.暂时将解密方法设置为NoPadding您的库使用的等效方法.这将使解密方法忽略填充错误,并为您提供一些输出.查看输出并将其与原始输入进行比较; 你可能需要在这里查看十六进制转储以确定发生了什么.

其中的可能性包括:

1. 输出是完全垃圾:您的密钥错误,或者流密码或GCM模式或CTR模式的IV/Nonce错误.

2. 第一个块是垃圾,其余块与明文匹配:你在CBC模式下有错误的IV.

3. 输出与最后的一些额外的东西匹配:额外的东西是填充.设置您的解密方法以期望填充类型.

如果这些都没有发生,那么请在这里再次询问,描述症状.

获得解决方案后,必须重新设置解密方法以获得正确的填充.将其设置为NoPadding不安全,因为任何旧垃圾都可以添加到解密的明文中.