Blowfish无效长度异常

Question

我正在用Blowfish算法加密我的文件，但我似乎对此一无所知。每当我尝试Encipher()时，它都会抛出一个异常，显示'Invalid Length‘。我计算出长度必须是0，当它被修改为8的时候，我认为这意味着应该有8乘8的流块来开始加密。我该怎么办？

Blowfish的加密方法：

public void Encipher(byte[] data, int length)
{
    uint xl, xr;
    if ((length % 8) != 0) <-- Exception Line
        throw new Exception("Invalid Length");
    for (int i = 0; i < length; i += 8)
    {
        // Encode the data in 8 byte blocks.
        xl = (uint)((data[i] << 24) | (data[i + 1] << 16) | (data[i + 2] << 8) | data[i + 3]);
        xr = (uint)((data[i + 4] << 24) | (data[i + 5] << 16) | (data[i + 6] << 8) | data[i + 7]);
        Encipher(ref xl, ref xr);
        // Now Replace the data.
        data[i] = (byte)(xl >> 24);
        data[i + 1] = (byte)(xl >> 16);
        data[i + 2] = (byte)(xl >> 8);
        data[i + 3] = (byte)(xl);
        data[i + 4] = (byte)(xr >> 24);
        data[i + 5] = (byte)(xr >> 16);
        data[i + 6] = (byte)(xr >> 8);
        data[i + 7] = (byte)(xr);
    }
}

我的加密方法：

private void EncryptFile(string szFilePath, string szInfoFile, string szKey, string szEncryptedFile = "")
        {
            // Blowfish
            Blowfish alg = new Blowfish(Encoding.Unicode.GetBytes(szKey));

            // Open file
            System.IO.FileStream originalStream = System.IO.File.OpenRead(szFilePath);

            // Store original file length
            long originalLength = originalStream.Length;
            System.IO.File.WriteAllText(szInfoFile, originalLength.ToString());

            Byte[] buffer = new byte[originalStream.Length + (originalStream.Length % 8)];
            originalStream.Read(buffer, 0, buffer.Length);
            originalStream.Close();

            // Encrypt
            alg.Encipher(buffer, buffer.Length);

            string szEncFile;

            if (szEncryptedFile != string.Empty) szEncFile = szEncryptedFile; else szEncFile = szFilePath;

            System.IO.FileStream stream = new System.IO.FileStream(szEncFile, System.IO.FileMode.Create);
            stream.Write(buffer, 0, buffer.Length);
            stream.Close(); 
        }

谢谢。

Answer 1

如果您要做的是将一个值向上舍入到可被8整除的下一个值，那么您应该这样做：

Byte[] buffer = new byte[originalStream.Length + (8-(originalStream.Length % 8))];

Answer 2

Peter Ritchie answered it。然而，下面有几个你应该考虑的习惯用法。一种是将IDisposable-implemented类(如FileStream)包装在using块中，以确保在处理过程中出现异常情况时处置资源。另一个是您放在一行中的if..then。这真的..。很奇怪。我已经将其替换为三元运算符，这似乎适合您使用的用法。祝你好运。

private void EncryptFile(string szFilePath, string szInfoFile, string szKey, string szEncryptedFile = "")
    {
        // Blowfish
        Blowfish alg = new Blowfish(Encoding.Unicode.GetBytes(szKey));

        // Open file
        using (System.IO.FileStream originalStream = System.IO.File.OpenRead(szFilePath))
        {
            // Store original file length
            long originalLength = originalStream.Length;
            System.IO.File.WriteAllText(szInfoFile, originalLength.ToString());

            Byte[] buffer = new byte[originalStream.Length + (originalStream.Length % 8)];
            originalStream.Read(buffer, 0, buffer.Length);
        }

        // Encrypt
        alg.Encipher(buffer, buffer.Length);

        string szEncFile;

        szEncFile = string.IsNullOrEmpty(szEncryptedFile) ? szFilePath : szEncryptedFile;

        using (System.IO.FileStream stream = new System.IO.FileStream(szEncFile, System.IO.FileMode.Create))
        {
            stream.Write(buffer, 0, buffer.Length);
        }
    }