c＃中的autokey vigenere解密

Question

这是我解密autokey vigenere密码算法的代码

string cipherText = "zicvtwqngkzeiigasxstslvvwla";
string key = "deceptive";

key = key.ToLower();
cipherText = cipherText.ToLower();

int klength = key.Length;
int kslength = (int)(cipherText.Length - key.Length);

string pl = string.Empty;
char[] newpl = new char[cipherText.Length];
int a = Convert.ToInt32('a');
for (int i = 0; i < cipherText.Length - kslength; i++)
{
    int c = Convert.ToInt32(cipherText[i]) - a;
    if (c< 0) c += 26;
    int k = Convert.ToInt32(key[i]) - a;
    if (k < 0) k += 26;
    int p = (c - k);
    p %= 26;
    if (p < 0) p += 26;
    p += a;
    char temp = Convert.ToChar(p);
    newpl[i] = temp;

}

char[] NewKey = new char[cipherText.Length];
char[] ciphertext = new char[cipherText.Length];
char[] chars = new char[cipherText.Length];
int count =0;
for (int i = 0; i < key.Length; i++)
{
    NewKey[i] = key[i];
    count++;
}
int j = 0;
for (int i = count; i < cipherText.Length; i++)
{
    NewKey[i] = newpl[j];
    j++;
}

Console.WriteLine(NewKey);

for (int i = klength; i < cipherText.Length; i++)
{
    int c = Convert.ToInt32(cipherText[i]) - a;
    int k = Convert.ToInt32(NewKey[i]) - a;
    int p = (c - k);
    p %= 26;
    if (p < 0) p += 26;
    p += a;

    char temp = Convert.ToChar(p);
    newpl[i] = temp;
}
pl = new string(newpl);
Console.WriteLine(pl);

它给了我输出：

deceptivewearedisc

wearediscoveredsavlmleoopet

而正确的输出应该是：

deceptivewearediscoveredsav

wearediscoveredsaveyourself

输出的第一行是指自动生成的键

第二行是指解密的文本。

Answer 1

代码中的错误很少：

1）看看这一行：

for (int i = 0; i < cipherText.Length - kslength; i++)

kslength = cipherText.Length - key.Length所以你的代码是

for (int i = 0; i < key.Length; i++)

密钥长度<小于文本长度，因此您太早完成解密。

2)

char temp = Convert.ToChar(p);
newpl[i] = temp;

您解密了符号，但使用自动密钥解密，您应该将解密符号添加到您的密钥。

3)

for (int i = 0; i < key.Length; i++)

应该是NewKey.Length，因为key比我们在修复＃2后真正需要的更长。

固定代码：

string cipherText = "zicvtwqngkzeiigasxstslvvwla";
string key = "deceptive";

key = key.ToLower();
cipherText = cipherText.ToLower();

int klength = key.Length;

string pl = string.Empty;
char[] newpl = new char[cipherText.Length];
int a = Convert.ToInt32('a');
for (int i = 0; i < cipherText.Length; i++)
{
    int c = Convert.ToInt32(cipherText[i]) - a;
    if (c < 0) c += 26;
    int k = Convert.ToInt32(key[i]) - a;
    if (k < 0) k += 26;
    int p = (c - k);
    p %= 26;
    if (p < 0) p += 26;
    p += a;
    char temp = Convert.ToChar(p);
    key += temp;
    newpl[i] = temp;

}

char[] NewKey = new char[cipherText.Length];
int count = 0;
for (int i = 0; i < NewKey.Length; i++)
{
    NewKey[i] = key[i];
    count++;
}
int j = 0;
for (int i = count; i < cipherText.Length; i++)
{
    NewKey[i] = newpl[j];
    j++;
}

Console.WriteLine(NewKey);

for (int i = klength; i < cipherText.Length; i++)
{
    int c = Convert.ToInt32(cipherText[i]) - a;
    int k = Convert.ToInt32(NewKey[i]) - a;
    int p = (c - k);
    p %= 26;
    if (p < 0) p += 26;
    p += a;

    char temp = Convert.ToChar(p);
    newpl[i] = temp;
}
pl = new string(newpl);
Console.WriteLine(pl);

输出：

deceptivewearediscoveredsav

wearediscoveredsaveyourself