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diff --git a/plugins/ao/eng_qsf/kabuki.c b/plugins/ao/eng_qsf/kabuki.c
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-/***************************************************************************
-
-"Kabuki" Z80 encryption
-
-
-The "Kabuki" is a custom Z80 module which runs encrypted code. The encryption
-key is stored in some battery-backed RAM, therefore the chip has the annoying
-habit of stopping working every few years, when the battery dies.
-Check at the bottom of this text to see a list of all the known games which
-use this chip.
-
-
-How it works:
-The base operation is a bit swap which affects couples of adjacent bits.
-Each of the 4 couples may or may not be swapped, depending on the address of
-the byte and on whether it is an opcode or data.
-The decryption consists of these steps:
-- bitswap
-- ROL
-- bitswap
-- XOR with a key
-- ROL
-- bitswap
-- ROL
-- bitswap
-
-To know how to apply the bit swap, take the address of the byte to decode and:
-- if the byte is an opcode, add addr_key to the address
-- if the byte is data, XOR the address with 1FC0, add 1, and then add addr_key
-You'll get a 16-bit word. The first two bitswaps depend on bits 0-7 of that
-word, while the second two on bits 8-15. When a bit in the word is 1, swap the
-two bits, oherwise don't. The exact couple of bits affected depends on the
-game and is identified in this file with two keys: swap_key1 and swap_key2
-(which are just permutations of the numbers 0-7, not full 32-bit integers).
-
-
-Key space size:
-- swap_key1 8! = 40320
-- swap_key2 8! = 40320
-- addr_key 2^16 = 65536
-- xor_key 2^8 = 256
-- total 2.7274 * 10^16
-
-
-Weaknesses:
-- 0x00 and 0xff, having all the bits set to the same value, are not affected
- by bit permutations after the XOR. Therefore, their encryption is the same
- regardless of the high 8 bits of the address, and of the value of
- swap_key2. If there is a long stream of 0x00 or 0xff in the original data,
- this can be used to find by brute force all the candidates for swap_key1,
- xor_key, and for the low 8 bits of addr_key. This is a serious weakness
- which dramatically reduces the security of the encryption.
-- A 0x00 is always encrypted as a byte with as many 1s as xor_key; a 0xff is
- always encrypted as a byte with as many 0s as xor_key has 1s. So you just
- need to know one 0x00 or 0xff in the unencrypted data to know how many 1s
- there are in xor_key.
-- Once you have restricted the range for swap_key1 and you know the number of
- 1s in the xor_key, you can easily use known plaintext attacks and brute
- force to find the remaining keys. Long strings like THIS GAME IS FOR USE IN
- and ABCDEFGHIJKLMNOPQRSTUVWXYZ can be found by comparing the number of 1s
- in the clear and encrypted data, taking xor_key into account. When you have
- found where the string is, use brute force to reduce the key space.
-
-
-Known games:
- swap_key1 swap_key2 addr_key xor_key
-Mahjong Gakuen 2 Gakuen-chou no Fukushuu 76543210 01234567 aa55 a5
-Poker Ladies " " " " "" ""
-Dokaben " " " " "" ""
-Dokaben 2 unknown
-Pang / Buster Bros / Pomping World 01234567 76543210 6548 24
-Capcom Baseball " " " " "" ""
-Capcom World 04152637 40516273 5751 43
-Adventure Quiz 2 Hatena ? no Dai-Bouken 45670123 45670123 5751 43
-Super Pang 45670123 45670123 5852 43
-Super Buster Bros 45670123 45670123 2130 12
-Super Marukin-Ban 54321076 54321076 4854 4f
-Quiz Tonosama no Yabou 12345670 12345670 1111 11
-Ashita Tenki ni Naare unknown
-Quiz Sangokushi 23456701 23456701 1828 18
-Block Block 02461357 64207531 0002 01
-
-Warriors of Fate 01234567 54163072 5151 51
-Cadillacs and Dinosaurs 76543210 24601357 4343 43
-Punisher 67452103 75316024 2222 22
-Slam Masters 54321076 65432107 3131 19
-
-***************************************************************************/
-
-#include "cpuintrf.h"
-
-static int bitswap1(int src,int key,int sel)
-{
- if (sel & (1 << ((key >> 0) & 7)))
- src = (src & 0xfc) | ((src & 0x01) << 1) | ((src & 0x02) >> 1);
- if (sel & (1 << ((key >> 4) & 7)))
- src = (src & 0xf3) | ((src & 0x04) << 1) | ((src & 0x08) >> 1);
- if (sel & (1 << ((key >> 8) & 7)))
- src = (src & 0xcf) | ((src & 0x10) << 1) | ((src & 0x20) >> 1);
- if (sel & (1 << ((key >>12) & 7)))
- src = (src & 0x3f) | ((src & 0x40) << 1) | ((src & 0x80) >> 1);
-
- return src;
-}
-
-static int bitswap2(int src,int key,int sel)
-{
- if (sel & (1 << ((key >>12) & 7)))
- src = (src & 0xfc) | ((src & 0x01) << 1) | ((src & 0x02) >> 1);
- if (sel & (1 << ((key >> 8) & 7)))
- src = (src & 0xf3) | ((src & 0x04) << 1) | ((src & 0x08) >> 1);
- if (sel & (1 << ((key >> 4) & 7)))
- src = (src & 0xcf) | ((src & 0x10) << 1) | ((src & 0x20) >> 1);
- if (sel & (1 << ((key >> 0) & 7)))
- src = (src & 0x3f) | ((src & 0x40) << 1) | ((src & 0x80) >> 1);
-
- return src;
-}
-
-static int bytedecode(int src,int swap_key1,int swap_key2,int xor_key,int sel)
-{
- src = bitswap1(src,swap_key1 & 0xffff,sel & 0xff);
- src = ((src & 0x7f) << 1) | ((src & 0x80) >> 7);
- src = bitswap2(src,swap_key1 >> 16,sel & 0xff);
- src ^= xor_key;
- src = ((src & 0x7f) << 1) | ((src & 0x80) >> 7);
- src = bitswap2(src,swap_key2 & 0xffff,sel >> 8);
- src = ((src & 0x7f) << 1) | ((src & 0x80) >> 7);
- src = bitswap1(src,swap_key2 >> 16,sel >> 8);
- return src;
-}
-
-static void kabuki_decode(unsigned char *src,unsigned char *dest_op,unsigned char *dest_data,
- int base_addr,int length,int swap_key1,int swap_key2,int addr_key,int xor_key)
-{
- int A;
- int sel;
-
- for (A = 0; A < length; A++)
- {
- /* decode opcodes */
- sel = (A + base_addr) + addr_key;
- dest_op[A] = bytedecode(src[A],swap_key1,swap_key2,xor_key,sel);
-
- /* decode data */
- sel = ((A + base_addr) ^ 0x1fc0) + addr_key + 1;
- dest_data[A] = bytedecode(src[A],swap_key1,swap_key2,xor_key,sel);
- }
-}
-
-void cps1_decode(unsigned char *rom, int swap_key1,int swap_key2,int addr_key,int xor_key)
-{
- int diff = (512*1024)/2;
-
- kabuki_decode(rom, rom+diff, rom, 0x0000, 0x8000, swap_key1, swap_key2, addr_key, xor_key);
-}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-07 05:21:21 +0000