Question

我得到“要解密的数据长度无效。”我试图解密内存流时的异常。我是初学者，不知道什么是错的。怎么了？

public bool EncryptStream()
    {

        string password = @"myKey123"; // Your Key Here
        UnicodeEncoding UE = new UnicodeEncoding();
        byte[] key = UE.GetBytes(password);

        s_EncryptedStream = new MemoryStream();
        int NoOfBytes;
        byte[] b_Buffer = new byte[8192];

        s_MemoryStream.Seek(0, SeekOrigin.Begin);

        RijndaelManaged RMCrypto = new RijndaelManaged();

        s_CrytpoStream = new CryptoStream(s_EncryptedStream,
            RMCrypto.CreateEncryptor(key, key),
            CryptoStreamMode.Write);

        while (s_MemoryStream.Length < s_MemoryStream.Position)
        {
            NoOfBytes = s_MemoryStream.Read(b_Buffer, 0, 8192);
            s_CrytpoStream.Write(b_Buffer, 0, NoOfBytes);
        }

        s_MemoryStream.Seek(0, SeekOrigin.Begin);

        while (s_EncryptedStream.Position < s_EncryptedStream.Length)
        {
            NoOfBytes = s_EncryptedStream.Read(b_Buffer, 0, 8192);
            s_MemoryStream.Write(b_Buffer, 0, NoOfBytes);

        }
        s_CrytpoStream.Flush();
        s_CrytpoStream.Close();

        return true;

    }


    public bool DecryptStream()
    {


        string password = @"myKey123"; // Your Key Here

        UnicodeEncoding UE = new UnicodeEncoding();
        byte[] key = UE.GetBytes(password);

        int NoOfBytes;
        byte[] b_Buffer = new byte[8192];

        s_DecryptedStream = new MemoryStream();


        RijndaelManaged RMCrypto = new RijndaelManaged();

        s_CrytpoStream = new CryptoStream(s_MemoryStream,
            RMCrypto.CreateDecryptor(key, key),
            CryptoStreamMode.Read);

        s_MemoryStream.Seek(0, SeekOrigin.Begin);

        while (s_MemoryStream.Length > s_MemoryStream.Position)
        {
            NoOfBytes = s_CrytpoStream.Read(b_Buffer, 0, 8192);
            s_DecryptedStream.Write(b_Buffer, 0, NoOfBytes);
        }

        s_DecryptedStream.Seek(0, SeekOrigin.Begin);
        s_MemoryStream.Seek(0, SeekOrigin.Begin);

        while (s_DecryptedStream.Position < s_DecryptedStream.Length)
        {
            NoOfBytes = s_DecryptedStream.Read(b_Buffer, 0, 8192);
            s_MemoryStream.Write(b_Buffer, 0, NoOfBytes);

        }

        s_CrytpoStream.Flush();
        s_CrytpoStream.Close();

        return true;

    }

Answer 1

首先，这个while循环条件永远不对：

while (s_MemoryStream.Length < s_MemoryStream.Position)

这个职位如何超越这个长度？

复制流的常用模式是重复读取，直到返回的值不是正数，而不是使用流的长度。正如你在这段代码中两次这样做的那样，你也可以将其封装起来：

public static void CopyStream(Stream input, Stream output)
{
    byte[] buffer = new byte[8192];
    int read;
    while ( (read = input.Read(buffer, 0, buffer.Length)) > 0)
    {
        output.Write(buffer, 0, read);
    }
}

最好使用using语句来清理字符串。此外，Encoding.Unicode属性意味着您不必自己创建新的UnicodeEncoding。另外，我通常发现设置Position属性比使用Seek更具可读性。最后，如果一个值总是为true，那么返回一个值是没有意义的。所以，你的代码将成为：

public void EncryptStream()
{
    string password = @"myKey123"; // Your Key Here
    byte[] key = Encoding.Unicode.GetBytes(password);

    s_EncryptedStream = new MemoryStream();
    s_MemoryStream.Position = 0;

    RijndaelManaged RMCrypto = new RijndaelManaged();

    using (Stream crytpoStream = new CryptoStream(s_EncryptedStream,
        RMCrypto.CreateEncryptor(key, key),
        CryptoStreamMode.Write))
    {
        CopyStream(s_MemoryStream, cryptoStream);
    }

    s_MemoryStream.Position = 0;
    s_EncryptedStream.Position = 0;
    CopyStream(s_EncryptedStream, s_MemoryStream);
}

public void DecryptStream()
{
    string password = @"myKey123"; // Your Key Here
    byte[] key = Encoding.Unicode.GetBytes(password);

    s_DecryptedStream = new MemoryStream();
    s_MemoryStream.Position = 0;

    RijndaelManaged RMCrypto = new RijndaelManaged();

    using (Stream crytpoStream = new CryptoStream(s_MemoryStream,
        RMCrypto.CreateDecryptor(key, key),
        CryptoStreamMode.Read))
    {
        CopyStream(cryptoStream, s_DecryptedStream);
    }

    s_DecryptedStream.Position = 0;
    s_MemoryStream.Position = 0;

    CopyStream(s_DecryptedStream, s_MemoryStream);
}

即使修改了这段代码，感觉就像你在这里有太多的非局部变量。我不明白为什么任何应该在实例变量中。使流加密或解密为参数（连同密码）并返回带有加密/解密数据的内存流，或仅返回字节数组。

Answer 2

阅读输入数据后，您可能需要在FlushFinalBlock上调用CryptoStream方法。（即CopyStream之后的crytpoStream.FlushFinalBlock()）

Answer 3

我已经提出了一个解决方案，并将其发布在我的新博客上

constotech.blogspot.com/2009/05/net-encryption-using-symmetricalgorithm.html

“要解密的数据长度无效。” Rijndael解密期间的异常

3 个答案: