[Coco] Copy Protection
Steve Ostrom
smostrom7 at comcast.net
Mon Jun 28 22:49:21 EDT 2010
I good friend of mine sent me a few disks that had some really great
programs on the disks. These programs are normally copy protected, but all
had the same scheme. If you type DIR, the directory is displayed but there
is also a title header in place of the first 10 or so lines of the
directory. This title was not spaced as if they were disk entries, but
looked just like a center-justified word processing document. Very neat.
One of the files on the disk was named "*". It contained a series of pokes
that created a small ML program. These same pokes were used for all of the
disks, no matter if they were Cer-Comp or Game Point Software. I
hand-disassembled the code - see below. I'm a bit rusty at this, but I
think that what I disassembled is close to accurate. Here is the code,
which is poked into address $01D1. I asssume this is the area of BASIC that
is hooked to auto start. Can anyone tell me exactly what is being done by
this code? Did I make any really bad disassembly blunders? I can't believe
that this snipit really defeats copy protection. Also, one of the disks was
definitely unprotected by Defeater by Carl England, but only one. The rest
used this scheme discussed above. Ideas???:
86 LDA#22
22
8E LDX#2600
26
00
8D BSR #0D -->A
0D
FC LDD $2600
26
00
10 CMPD #4F53
83
4F
53
26 BNE #03 -->E
03
7E JMP $2602
26
02
E 39 RTS
A 34 PSHS #2010
20
10
BE LDX $C006
C0
06
A7 STA 2,Y
22
86 LDA #02
02
A7 STA ,Y
A4
6F CLR 1,Y
21
6F CLR 3,Y
23
6C INC 3,Y
23
AF STX 4,Y
24
D 10 LDY $C006
BE
C0
06
A6 LDA 3,Y
23
81 CMPA #13
13
27 BEQ #12 -->B
12
AD JSR [$C004]
9F
C0
04
4D TST A
27 BEQ #06 -->C
06
6C INC 3,Y
23
6C INC 4,Y
24
20 BRA #E9 -->D
E9
C 7F CLR $FF40
FF
40
35 PULS #A0
A0
B 4F CLR A
20 BRA #F8 -->C
F8
Thanks!!
-- Steve --
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