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pengo.cpp: schick decryption WIP (nw)

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Ivan Vangelista 2019-04-10 17:55:56 +02:00
parent 5bd849d96f
commit 8477c1229b
1 changed files with 76 additions and 1 deletions
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77
src/mame/drivers/pengo.cpp
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@ -927,7 +927,7 @@ void pengo_state::init_penta()
void pengo_state::decode_schick_extra(int size, uint8_t* rom)
{
// schick has an extra layer of encryption in addition to the penta encryption
for (int A = 0x0000; A < 0x10000; A++)
for (int A = 0x0000; A < 0x8000; A++)
{
uint8_t srcdec = rom[A];
@ -943,6 +943,81 @@ void pengo_state::decode_schick_extra(int size, uint8_t* rom)
rom[A] = srcdec;
}
for (int A = 0x8000; A < 0x10000; A++)
{
uint8_t srcdec = rom[A];
/* if we assume only bits we've seen changed by the 2nd layer are chagned by this then our bitswap possibilities are
6, 4, 0
6, 0, 4
4, 6, 0
4, 0, 6
0, 4, 6
0, 6, 4
and XOR possibilities are
00
01
10
11
40
41
50
51
*/
// copy+paste these + modify
//rom[A] = bitswap<8>(srcdec ^ xx, 7, 0, 5, 6, 3, 2, 1, 4);
//rom[A] = bitswap<8>(srcdec ^ xx, 7, 0, 5, 4, 3, 2, 1, 6);
//rom[A] = bitswap<8>(srcdec ^ xx, 7, 4, 5, 0, 3, 2, 1, 6);
//rom[A] = bitswap<8>(srcdec ^ xx, 7, 4, 5, 6, 3, 2, 1, 0);
//rom[A] = bitswap<8>(srcdec ^ xx, 7, 6, 5, 0, 3, 2, 1, 4);
//rom[A] = bitswap<8>(srcdec ^ xx, 7, 6, 5, 4, 3, 2, 1, 0); // no swap
if (rom == m_decrypted_opcodes)
{
// these are wrong
if (A & 0x1000) // might be more conditions too, but there's certainly a boundary at efff-f000 (jump table)
{
//rom[A] = bitswap<8>(srcdec ^ 0x10, 7, 0, 5, 6, 3, 2, 1, 4); // NO
rom[A] = bitswap<8>(srcdec ^ 0x10, 7, 0, 5, 4, 3, 2, 1, 6); // potential, but no
//rom[A] = bitswap<8>(srcdec ^ 0x10, 7, 4, 5, 0, 3, 2, 1, 6); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x10, 7, 4, 5, 6, 3, 2, 1, 0); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x10, 7, 6, 5, 0, 3, 2, 1, 4); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x10, 7, 6, 5, 4, 3, 2, 1, 0); // potential, but no (no swap)
//rom[A] = bitswap<8>(srcdec ^ 0x11, 7, 0, 5, 6, 3, 2, 1, 4); // NO(?)
//rom[A] = bitswap<8>(srcdec ^ 0x11, 7, 0, 5, 4, 3, 2, 1, 6); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x11, 7, 4, 5, 0, 3, 2, 1, 6); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x11, 7, 4, 5, 6, 3, 2, 1, 0); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x11, 7, 6, 5, 0, 3, 2, 1, 4); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x11, 7, 6, 5, 4, 3, 2, 1, 0);
}
else
{
//rom[A] = bitswap<8>(srcdec ^ 0x51, 7, 0, 5, 6, 3, 2, 1, 4); // NO
rom[A] = bitswap<8>(srcdec ^ 0x51, 7, 0, 5, 4, 3, 2, 1, 6); // promising, but no
//rom[A] = bitswap<8>(srcdec ^ 0x51, 7, 4, 5, 0, 3, 2, 1, 6); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x51, 7, 4, 5, 6, 3, 2, 1, 0); // NO
//rom[A] = bitswap<8>(srcdec ^ 0x51, 7, 6, 5, 0, 3, 2, 1, 4); // NO
// rom[A] = bitswap<8>(srcdec ^ 0x51, 7, 6, 5, 4, 3, 2, 1, 0); promising, but no (no swap)
}
}
else
{
// these are correct(?) give good text, good jump locations etc.
if (A & 0x10)
srcdec = bitswap<8>(srcdec ^ 0x11, 7, 0, 5, 6, 3, 2, 1, 4);
else
srcdec = bitswap<8>(srcdec ^ 0x51, 7, 4, 5, 0, 3, 2, 1, 6);
rom[A] = srcdec;
}
}
}
void pengo_state::init_schick()