/*
    NitroHax -- Cheat tool for the Nintendo DS
    Copyright (C) 2008  Michael "Chishm" Chisholm

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <string.h>
#include "encryption.h"
#include "key1.h"
#include "key2.h"
#include "tonccpy.h"

#define KEYSIZE 0x1048

static u32 keycode [3];
static u32 keybuf [KEYSIZE/sizeof(u32)];

void crypt_64bit_up (u32* ptr) {
	u32 x = ptr[1];
	u32 y = ptr[0];
	u32 z;
	int i;

	for (i = 0; i < 0x10; i++) {
		z = keybuf[i] ^ x;
		x = keybuf[0x012 + ((z>>24)&0xff)];
		x = keybuf[0x112 + ((z>>16)&0xff)] + x;
		x = keybuf[0x212 + ((z>> 8)&0xff)] ^ x;
		x = keybuf[0x312 + ((z>> 0)&0xff)] + x;
		x = y ^ x;
		y = z;
	}

	ptr[0] = x ^ keybuf[0x10];
	ptr[1] = y ^ keybuf[0x11];
}

void crypt_64bit_down (u32* ptr) {
	u32 x = ptr[1];
	u32 y = ptr[0];
	u32 z;
	int i;
	
	for (i = 0x11; i > 0x01; i--) {
		z = keybuf[i] ^ x;
		x = keybuf[0x012 + ((z>>24)&0xff)];
		x = keybuf[0x112 + ((z>>16)&0xff)] + x;
		x = keybuf[0x212 + ((z>> 8)&0xff)] ^ x;
		x = keybuf[0x312 + ((z>> 0)&0xff)] + x;
		x = y ^ x;
		y = z;
	}

	ptr[0] = x ^ keybuf[0x01];
	ptr[1] = y ^ keybuf[0x00];
}

static u32 bswap_32bit (u32 in) {
	u8 a,b,c,d;
	a = (u8)((in >>  0) & 0xff);
	b = (u8)((in >>  8) & 0xff);
	c = (u8)((in >> 16) & 0xff);
	d = (u8)((in >> 24) & 0xff);

	u32 out = (a << 24) | (b << 16) | (c << 8) | (d << 0);

	return out;
}

void apply_keycode (u32 modulo) {
	u32 scratch[2];
	int i;
	modulo = modulo / sizeof(*keycode);

	crypt_64bit_up (&keycode[1]);
	crypt_64bit_up (&keycode[0]);
	toncset (scratch, 0, 8);

	for (i = 0; i < 0x12; i+=1) {
		keybuf[i] = keybuf[i] ^ bswap_32bit (keycode[i % modulo]);
	}
	for (i = 0; i < 0x412; i+=2) {
		crypt_64bit_up (scratch);
		keybuf[i]   = scratch[1];
		keybuf[i+1] = scratch[0];
	}
}

void init_keycode (u32 idcode, u32 level, u32 modulo, int iCardDevice) {
	tonccpy ((u8*)keybuf, (iCardDevice ? gEncrDataTwl : gEncrData), KEYSIZE);
	keycode[0] = idcode;
	keycode[1] = idcode/2;
	keycode[2] = idcode*2;

	if (level >= 1) apply_keycode (modulo);	// first apply (always)
	if (level >= 2) apply_keycode (modulo);	// second apply (optional)
	keycode[1] = keycode[1] * 2;
	keycode[2] = keycode[2] / 2;
	if (level >= 3) apply_keycode (modulo);	// third apply (optional)
}