CryEntryBuffer

struct rc4_state
{
    int x, y, m[256];
};

void rc4_setup(struct rc4_state *s, unsigned char *key, int length)
{
	int i, j, k, *m, a;

	s->x = 0;
	s->y = 0;
	m = s->m;

	for(i = 0; i < 256; i++)
	{
		m[i] = i;
	}

	j = k = 0;

	for(i = 0; i < 256; i++)
	{
		a = m[i];
		j = (unsigned char) (j + a + key[k]);
		m[i] = m[j]; m[j] = a;
		if(++k >= length) k = 0;
	}
}

//******************************************************************************

void rc4_crypt( struct rc4_state *s, unsigned char *data, int length)
{ 
	int i, x, y, *m, a, b;

	x = s->x;
	y = s->y;
	m = s->m;

	for( i = 0; i < length; i++)
	{
		x = (unsigned char) (x + 1); a = m[x];
		y = (unsigned char) (y + a);
		m[x] = b = m[y];
		m[y] = a;
		data[i] ^= m[(unsigned char) (a + b)];
	}

	s->x = x;
	s->y = y;
}

BOOL EntryptionBuf(char* Buf, DWORD dwlen)
{
	BYTE rc4_key[8] = {0x01,0x23,0x45,0x67,0x89,0xAB,0xCD,0xEF};
	rc4_state rc4_test;		
	memset(&rc4_test, 0, sizeof(rc4_test));

	try
	{
		rc4_setup(&rc4_test, rc4_key, 8);
		rc4_crypt(&rc4_test, (unsigned char*)Buf, dwlen);
	}
	catch (...)
	{
		return FALSE;		
	}

	return TRUE;
}

int main()
{
   EntryptionBuf(youBuf,youBufSize);
}