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just some code to help analyse this encryption (nw)

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This commit is contained in:
David Haywood 2013-06-01 10:07:30 +00:00
parent e3751322cd
commit 729d3b48b9
1 changed files with 67 additions and 5 deletions
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72
src/mame/drivers/speedbal.c
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@ -354,6 +354,7 @@ ROM_START( speedbal )
ROM_LOAD( "sb6.bin", 0x08000, 0x08000, CRC(0e2506eb) SHA1(56f779266b977819063c475b84ca246fc6d8d6a7) )
ROM_END
//#define USE_DECRYPTION_HELPER
ROM_START( musicbal )
ROM_REGION( 0x10000, "maincpu", 0 ) /* 64K for code: main - encrypted */
@ -375,8 +376,24 @@ ROM_START( musicbal )
ROM_REGION( 0x10000, "gfx3", ROMREGION_INVERT ) // still contain Speed Ball logos!
ROM_LOAD( "07.bin", 0x00000, 0x08000, CRC(310e1e23) SHA1(290f3e1c7b907165fe60a4ebe7a8b04b2451b3b1) ) /* sprites */
ROM_LOAD( "06.bin", 0x08000, 0x08000, CRC(2e7772f8) SHA1(caded1a72356501282e627e23718c30cb8f09370) )
#ifdef USE_DECRYPTION_HELPER
/* speed ball code for decryption comparison help */
ROM_REGION( 0x10000, "helper", 0 )
ROM_LOAD( "sb1.bin", 0x0000, 0x8000, CRC(1c242e34) SHA1(8b2e8983e0834c99761ce2b5ea765dba56e77964) )
ROM_LOAD( "sb3.bin", 0x8000, 0x8000, CRC(7682326a) SHA1(15a72bf088a9adfaa50c11202b4970e07c309a21) )
#endif
ROM_END
#define MUSICBALL_XOR05 { rom[i] = rom[i] ^ 0x05; }
#define MUSICBALL_XOR84 { rom[i] = rom[i] ^ 0x84; }
#define MUSICBALL_SWAP1 { rom[i] = BITSWAP8(rom[i],2,6,5,4,3,7,0,1); }
#define MUSICBALL_SWAP2 { rom[i] = BITSWAP8(rom[i],7,6,5,4,3,0,2,1); }
// are bits 6,5,4,3 affected, or does this work on only the 4 bits?
DRIVER_INIT_MEMBER(speedbal_state,musicbal)
{
UINT8* rom = memregion("maincpu")->base();
@ -385,16 +402,61 @@ DRIVER_INIT_MEMBER(speedbal_state,musicbal)
for (int i=0;i<0x8000;i++)
{
rom[i] = rom[i] ^ 0x84;
// some bits are ^ 0x05
/*if ((i&0x30) == 0x00)
{
if ((( i & 0x0f ) > 0x08) && (( i & 0x0f ) < 0x0f)) MUSICBALL_XOR05
}
*/
if (i&0x0020) { rom[i] = BITSWAP8(rom[i],2,6,5,4,3,7,0,1); }
else { rom[i] = BITSWAP8(rom[i],7,6,5,4,3,0,2,1); }
if (i&0x0020) { MUSICBALL_XOR84 MUSICBALL_SWAP1 }
else
{
if (i&0x08) { MUSICBALL_XOR84 MUSICBALL_SWAP2 }
else { MUSICBALL_SWAP1 }
}
}
#ifdef USE_DECRYPTION_HELPER
UINT8* helper = memregion("helper")->base();
int speedball_position = 0x590c; // a block of text that should mostly match here (terminators seem to be changed 1F 60 <-> DD 52 tho)
int musicball_position = 0x6610; // it's mostly the pattern of where xor 0x05 gets applied we're interested in
int blocklength = 0x2e0; // there is a clear change in pattern > 6800
if (helper)
{
int bytecount = 0;
for (int i=0;i<blocklength;i++)
{
UINT8 music = rom[musicball_position+i];
UINT8 speed = helper[speedball_position+i];
if (bytecount==0) printf("%04x: ", musicball_position+i);
UINT8 display = music ^ speed;
// filter out the terminators
if (display == 0xc2) display = 0x00;
if (display == 0x32) display = 0x00;
if (display == 0xc7) display = 0x05;
if (display == 0x37) display = 0x05;
//printf("%02x-%02x, ", music, speed);
printf("%02x, ", display);
bytecount++;
if (bytecount==16) { bytecount = 0; printf("\n"); }
}
}
#if 0
{
FILE *fp;
char filename[256];