如何解密简单的XOR加密 [英] How to decrypt simple XOR encryption

问题描述

我发现在互联网上以下XOR加密功能：

I found the following XOR encryption function on the internet:

void xor_encrypt(char *key, char *string)
{
    int i, string_length = strlen(string);
    for(i=0; i<string_length; i++)
    {
        string[i]=string[i]^key[i];
        printf("%i", string[i]);
    }
}

这完美的作品，但我想也解密字符串。

It works perfect, but I would like to decrypt the string also.

例如：

void xor_decrypt(char *key, char *encrypted_string)
{
    //decrypt method goes here
}

所以基本上我后加密字符串，我会使用相同的加密密钥来解密previously加密的字符串。

So basically after I encrypt the string, I would use the same encryption key to decrypt the previously encrypted string.

我是pretty新的节目，我只是想知道如何解密previously加密的字符串。感谢所有帮助AP preciated。

I'm pretty new to programming and I would just like to know how to decrypt the previously encrypted string. Thanks, all help is appreciated.

推荐答案

一个关于XOR加密很酷的事情是，当你申请两次，你回来原始的字符串 - 看的http://en.wikipedia.org/wiki/XOR_cipher 。

One of the cool things about XOR encryption is that when you apply it twice, you get back the original string – see http://en.wikipedia.org/wiki/XOR_cipher.

在你的函数，xor_decrypt，你把字符串键和返回的字符串^键。如果，现在，你异或与一次该键，你会得到（字符串^键）^键=字符串^（^键键）=串^身份=字符串
（通过XOR运算符的属性：<一个href=\"http://en.wikipedia.org/wiki/Exclusive_or#Properties\">http://en.wikipedia.org/wiki/Exclusive_or#Properties)

In your function, xor_decrypt, you take string and key and return string ^ key. If, now, you xor that with the key again, you get (string ^ key) ^ key = string ^ (key ^ key) = string ^ identity = string (by properties of XOR operator: http://en.wikipedia.org/wiki/Exclusive_or#Properties)

因此​​，你可以运行你的函数，xor_encrypt，就先xor_encrypt输出第二次。

Thus, you can just run your function, xor_encrypt, a second time on the output of the first xor_encrypt.

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