Question

我正在尝试“解码”以下Base64字符串：

OBFZDTcPCxlCKhdXCQ0kMQhKPh9uIgYIAQxALBtZAwUeOzcdcUEeW0dMO1kbPElWCV1ISFFKZ0kdWFlLAURPZhEFQVseXVtPOUUICVhMAzcfZ14AVEdIVVgfAUIBWVpOUlAeaUVMXFlKIy9rGUN0VF08Oz1POxFfTCcVFw1LMQNbBQYWAQ ==

这就是我对字符串本身的了解：

原始字符串首先通过以下代码传递：

private static string m000493(string p0, string p1)
{
    StringBuilder builder = new StringBuilder(p0);
    StringBuilder builder2 = new StringBuilder(p1);
    StringBuilder builder3 = new StringBuilder(p0.Length);
    int num = 0;
Label_0084:
    while (num < builder.Length)
    {
        int num2 = 0;
        while (num2 < p1.Length)
        {
            if ((num == builder.Length) || (num2 == builder2.Length))
            {
                MessageBox.Show("EH?");
                goto Label_0084;
            }
            char ch = builder[num];
            char ch2 = builder2[num2];
            ch = (char)(ch ^ ch2);
            builder3.Append(ch);
            num2++;
            num++;
        }
    }
    return m0001cd(builder3.ToString());
}

代码中的p1部分应为字符串“_p0lizei.”。

然后通过以下代码将其转换为Base64字符串：

private static string m0001cd(string p0)
{
    string str2;
    try
    {
        byte[] buffer = new byte[p0.Length];
        str2 = Convert.ToBase64String(Encoding.UTF8.GetBytes(p0));
    }
    catch (Exception exception)
    {
        throw new Exception("Error in base64Encode" + exception.Message);
    }
    return str2;
}

问题是，我如何解码Base64字符串，以便找出原始字符串是什么？

Answer 1

简单：

byte[] data = Convert.FromBase64String(encodedString);
string decodedString = Encoding.UTF8.GetString(data);

Answer 2

m000493方法似乎执行某种XOR加密。这意味着可以使用相同的方法来加密和解密文本。您所要做的就是撤消m0001cd：

string p0 = Encoding.UTF8.GetString(Convert.FromBase64String("OBFZDT..."));

string result = m000493(p0, "_p0lizei.");
//    result == "gaia^unplugged^Ta..."

将return m0001cd(builder3.ToString());更改为return builder3.ToString();。

如何解码base64编码的字符串？

2 个答案: