Question

我只能加密，但我不知道如何解密。有人请帮忙。我必须声明一个bool变量吗？或者是其他更好的方法吗？

                string UserInput = "";
                int shift;
                Shift OBSHIFT = new Shift();
                Console.Write("\nType a string to encrypt:");
                UserInput = Console.ReadLine();
                Console.Write("How many chars would you like to shift?: ");
                shift = int.Parse(Console.ReadLine());
                Console.WriteLine("\nApplying Caesar cipher ... ");
                Console.Write("Your encrypted string is: ");
                Console.WriteLine(OBSHIFT.Cshift(UserInput, shift));
                Console.Read();
        }
    }
class Shift
{
    public string Cshift(string str, int shift )
    {
        string UserOutput = "";
        char[] A = null;
        A = str.ToCharArray();
        int temp;
        for (int i = 0; i < str.Length; i++)
        {
            char c = A[i];
            if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'))
            {
                temp = (int)(A[i] + shift);
                if ((c >= 'A' && c <= 'Z' && temp > 'Z') || (c >= 'a' && c <= 'z' && temp > 'z'))
                    temp = temp - 26;
                else
                    temp = (int)(A[i] + (shift));
            }
            else
                temp = c;
            UserOutput += (char)temp;
        }
        return UserOutput;
    }
}

}

Answer 1

谈到凯撒密码，你可以简单地否定shift并获得原始字符串。

即，cshift(cshift(string, x), -x) == string。

使用您的Shift课程：

int sh = 17;
string original = "abcdefgh";

string encrypted = shift.Cshift(original, sh);
string decrypted = shift.Cshift(shifted, -sh);

Console.WriteLine(decrypted == original); // true

为方便起见，您可以创建一个方法Decrypt，它将执行此操作：

class Shift
{
    public string Encrypt(string originalString, int shift)
    {
        string userOutput = "";
        char[] a = originalString.ToCharArray();
        for (int i = 0; i < originalString.Length; i++)
        {
            char c = a[i];
            int temp;
            if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'))
            {
                temp = (int)(a[i] + shift);
                if ((c >= 'A' && c <= 'Z' && temp > 'Z') || (c >= 'a' && c <= 'z' && temp > 'z'))
                    temp = temp - 26;
                else
                    temp = (int)(a[i] + (shift));
            }
            else
                temp = c;
            userOutput += (char)temp;
        }
        return userOutput;
    }

    public string Decrypt(string cipherString, int shift)
    {
        return Encrypt(cipherString, -shift);
    }
}

请注意，我还做了一些代码改进，例如：

合并A
将temp移至内部范围
为局部变量（小写）

如何在没有特殊字符的情况下为我的解密编写代码

1 个答案: