我是android的新手。我正在做一个应用程序,它可以将加密的png图像文件下载到SD卡,然后在解密后显示它。但是我注意到在解密下载的图像时我得到了“javax.crypto.IllegalBlockSizeException: last block incomplete in decryption image decryption
”。然后我发现下载的图像大小为0KB(原始 - 150KB)。然后我从浏览器下载了加密图像并进行了检查。我得到原始图像大小。我确定我的图像下载课有问题。但我无法弄明白。请帮我。提前谢谢。
图像下载AsyncTask类
public class DownloadImagesTask extends AsyncTask<String, Void, Bitmap>
{
private String fileName;
@Override
protected Bitmap doInBackground(String... urls)
{
//Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
return download_Image(urls[0]);
}
@Override
protected void onPostExecute(Bitmap result)
{
storeImage(result);
}
private Bitmap download_Image(String url)
{
Bitmap bm = null;
File file = new File(url);
fileName = file.getName();
try
{
URL aURL = new URL(url);
URLConnection conn = aURL.openConnection();
conn.connect();
InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
bm = BitmapFactory.decodeStream(bis);
bis.close();
is.close();
}
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 bm;
}
public void storeImage(Bitmap bm)
{
BitmapFactory.Options bmOptions;
bmOptions = new BitmapFactory.Options();
bmOptions.inSampleSize = 1;
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
{
bm.compress(Bitmap.CompressFormat.PNG, 100, outStream);
outStream.flush();
outStream.close();
Log.d("ScratchActivtiy", "Image Saved");
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
}
(所有图片都是由我加密的。我将它们托管在服务器中。加密或解密都没有问题。我测试了它们。一切正常。)
CryptClass
public class CryptClass
{
public byte[] encrypt(String seed, byte[] cleartext) throws Exception
{
byte[] rawKey = getRawKey(seed.getBytes());
byte[] result = encrypt(rawKey, cleartext);
// return toHex(result);
return result;
}
public byte[] decrypt(String seed, byte[] encrypted) throws Exception
{
byte[] rawKey = getRawKey(seed.getBytes());
byte[] enc = encrypted;
byte[] result = decrypt(rawKey, enc);
return result;
}
//done
private byte[] getRawKey(byte[] seed) throws Exception
{
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(seed);
kgen.init(128, sr);
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}
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;
}
private byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception
{
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
byte[] decrypted = cipher.doFinal(encrypted);
return decrypted;
}
}
答案 0 :(得分:2)
如果我理解正确您首先下载图像
BufferedInputStream bis = new BufferedInputStream(is);
bm = BitmapFactory.decodeStream(bis);
然后将其保存到PNG压缩文件:
bm.compress(Bitmap.CompressFormat.PNG, 100, outStream);
在对文件进行解密之后,对吧?
我认为您可能希望在将字节保存为png之前解密字节,甚至可能在使用decodeStream之前解密。否则,您正在解密解码流和PNG压缩的加密字节。
尝试跳过所有BitmapFactory内容,然后按原样保存初始文件,然后运行解密。在AsyncTask中:
String saveFilePath = <path to the temporary encrypted file>;
FileOutputStream outputStream = new FileOutputStream(saveFilePath);
int bytesRead = -1;
byte[] buffer = new byte[4096];
while ((bytesRead = is.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();
然后在保存的文件上运行解密内容