hey can anyone help me with the decrypt part...cant seem to get it to work....
#include <iostream>
using namespace std;
unsigned char s[256];
unsigned int i, j;
void swap(unsigned char *s, unsigned int i, unsigned int j)
{
unsigned char temp = s[i];
s[i] = s[j];
s[j] = temp;
}
void rc4_KSA (const char *key, unsigned int keylen)
{
int a=0, b=0;
for (a = 0; a < 256; a++)
{
s[a] = a;
}
for (a = 0, b = 0; a < 256; a++)
{
b = (b + key[a % keylen ] + s[a]) % 256;
swap(s, a , b);
}
}
unsigned char rc4_PRGA()
{
i = (i + 1) % 256;
j = (j + s[i]) % 256;
swap(s, i, j);
return s[(s[i] + s[j]) % 256];
}
int main()
{
string input;
string plainText;
do {
cout << "Please enter a 16 character key (signifying 16 bytes):";
getline(cin, input);
if (input.length() > 16)
{
cout << "Entered key is more than 16 characters." <<endl;
}
else
{
break;
}
} while (true);
const char* key = input.c_str();
//create the keystream
rc4_KSA(key, strlen(key));
cout << "Generated Key stream:" << endl;
for (int t = 0; t < 256; t++)
{
cout << s[t];
}
cout << endl;
//plaintext is taken from user.
cout << "Enter plain text (upto 1024 characters long):";
getline(cin, plainText);
int size = plainText.length();
//allocate new memory blocks to hold the data
const char* memblock = plainText.c_str();
char* enblock = new char [size];
//encrypt
for (int x = 0; x < size; x++)
{
enblock[x] = (memblock[x] ^ rc4_PRGA());
}
cout << "Generated Encrypted stream:" << endl;
for (int y = 0; y < size; y++)
{
cout << enblock[y];
}
cout << endl;
system("pause");
//reset keyStream (s array)
rc4_KSA(key,strlen(key));
//decrypt
for (int x = 0; x < size; x++)
{
enblock[x] = (enblock[x] ^ rc4_PRGA());
}
//print out the plaintext
for (int x = 0; x < size; x++)
{
cout << enblock[x];
}
delete[] memblock;
delete[] enblock;
return 0;
}
thanks
