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]);
}
}
It works perfect, but I would like to decrypt the string also.
For example:
void xor_decrypt(char *key, char *encrypted_string)
{
//decrypt method goes here
}
So basically after I encrypt the string, I would use the same encryption key to decrypt the previously encrypted string.
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.
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.
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)
Thus, you can just run your function, xor_encrypt, a second time on the output of the first xor_encrypt.
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