Question

我有两个用于计算SHA1的小片段。

一个是非常快但似乎它不正确而另一个非常慢但是正确我认为FileInputStream转换为ByteArrayInputStream是问题所在。

快速版：

MessageDigest md = MessageDigest.getInstance("SHA1");
FileInputStream fis = new FileInputStream("path/to/file.exe");
ByteArrayInputStream byteArrayInputStream =
    new ByteArrayInputStream(fis.toString().getBytes());
DigestInputStream dis = new DigestInputStream(byteArrayInputStream, md);
BufferedInputStream bis = new BufferedInputStream(fis);
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

int ch;
while ((ch = dis.read()) != -1) {
    byteArrayOutputStream.write(ch);
}

byte[] newInput = byteArrayOutputStream.toByteArray();
System.out.println("in digest : " +
    byteArray2Hex(dis.getMessageDigest().digest()));

byteArrayOutputStream = new ByteArrayOutputStream();
DigestOutputStream digestOutputStream =
    new DigestOutputStream(byteArrayOutputStream, md);
digestOutputStream.write(newInput);

System.out.println("out digest: " +
    byteArray2Hex(digestOutputStream.getMessageDigest().digest()));
System.out.println("length: " + 
    new String(
        byteArray2Hex(digestOutputStream.getMessageDigest().digest())).length());

digestOutputStream.close();
byteArrayOutputStream.close();
dis.close();

慢版：

MessageDigest algorithm = MessageDigest.getInstance("SHA1");
FileInputStream fis = new FileInputStream("path/to/file.exe");
BufferedInputStream bis = new BufferedInputStream(fis);
DigestInputStream   dis = new DigestInputStream(bis, algorithm);

// read the file and update the hash calculation
while (dis.read() != -1);

 // get the hash value as byte array
byte[] hash = algorithm.digest();

转换方法：

private static String byteArray2Hex(byte[] hash) {
    Formatter formatter = new Formatter();
    for (byte b : hash) {
        formatter.format("%02x", b);
    }
    return formatter.toString();
}

我希望有另一种可能性让它运行，因为我需要性能。

Answer 1

这样做：

MessageDigest md = MessageDigest.getInstance("SHA1");
InputStream in = new FileInputStream("hereyourinputfilename");
byte[] buf = new byte[8192];
for (;;) {
    int len = in.read(buf);
    if (len < 0)
        break;
    md.update(buf, 0, len);
}
in.close();
byte[] hash = md.digest();

性能来自于按块处理数据。这里的8 kB缓冲区应该足够块。您不必使用BufferedInputStream，因为8 kB缓冲区也可用作I / O缓冲区。

Answer 2

快速且不正确的原因是（我认为）它没有散列文件内容！

FileInputStream fis = new FileInputStream("C:/Users/Ich/Downloads/srware_iron.exe");
ByteArrayInputStream byteArrayInputStream = 
        new ByteArrayInputStream(fis.toString().getBytes());

fis.toString()调用不会读取文件的内容。相反，它给你一个字符串（我怀疑）看起来像这样：

"java.io.FileInputStream@xxxxxxxx"

然后您继续计算SHA1哈希值。 FileInputStream及其超类不会覆盖Object::toString ...

将InputStream的全部内容读取到byte[]的简单方法是使用Apache Commons I / O辅助方法 - IOUtils.toByteArray(InputStream)。

Answer 3

    public void computeSHAHash(String path)// path to your file
    {
            String SHAHash = null;
    try 
    {
        MessageDigest md = MessageDigest.getInstance("SHA1");
        InputStream in = new FileInputStream(path);
        byte[] buf = new byte[8192];
        int len = -1;
        while((len = in.read(buf)) > 0) 
        {
            md.update(buf, 0, len);
        }
        in.close();
        byte[] data = md.digest();
        try 
        {
           SHAHash = convertToHex(data);
        } 
        catch (IOException e) 
        {
           // TODO Auto-generated catch block
           e.printStackTrace();
        }
    } catch (NoSuchAlgorithmException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
      Toast.makeToast(getApplicationContext(),"Generated Hash ="+SHAHash,Toast.LENGTH_SHORT).show();  

   }
 private static String convertToHex(byte[] data) throws java.io.IOException
{
    StringBuffer sb = new StringBuffer();
    String hex = null;

    hex = Base64.encodeToString(data, 0, data.length, NO_OPTIONS);

    sb.append(hex);

    return sb.toString();
}

Android中SHA1哈希实现的问题

4 个答案: