-----------------Thwart----------------
A 4am crack                  2016-04-25
---------------------------------------

Name: Thwart
Genre: educational
Year: 1984
Publisher: Random House, Inc.
Media: single-sided 5.25-inch floppy
OS: DOS 3.3
Previous cracks: none
Identical cracks:
  #674 Word Walk
  #647 Galaxy Math
  #467 Snoopy To The Rescue
  #441 Garfield Double Dares
  #188 Garfield, Eat Your Words

                   ~

               Chapter 0
 In Which Various Automated Tools Fail
          In Interesting Ways


COPYA
  immediate disk read error

Locksmith Fast Disk Backup
  unable to read any track

EDD 4 bit copy (no sync, no count)
  copy works

Copy ][+ nibble editor
  all tracks use standard prologues
  (address: D5 AA 96, data: D5 AA AD)
  but modified address epilogue
  (AA DE EB instead of DE AA EB)

Disk Fixer
  ["O" -> "Input/Output Control"]
    set Address Epilogue to "AA DE EB"
  Success! All tracks readable!
  T00 -> looks like a DOS 3.3 RWTS
  T11 -> DOS 3.3 disk catalog
  T01,S09 -> startup program is "STEX"

Why didn't COPYA work?
  modified epilogue bytes (every track)

Why didn't Locksmith FDB work?
  modified epilogue bytes (every track)

EDD worked. What does that tell us?
  probably just structural protection
  (modified epilogue), no nibble check

Next steps:

  1. capture RWTS with AUTOTRACE
  2. convert disk to standard format
     with Advanced Demuffin
  3. patch RWTS to read standard format

                   ~

               Chapter 1
In Which We Attempt To Use The Original
    Disk As A Weapon Against Itself


[S6,D1=original disk]
[S6,D2=blank disk]
[S5,D1=my work disk]

]PR#5
CAPTURING BOOT0
...reboots slot 6...
...reboots slot 5...
SAVING BOOT0
CAPTURING BOOT1
...reboots slot 6...
...reboots slot 5...
SAVING BOOT1
SAVING RWTS

]BRUN ADVANCED DEMUFFIN 1.5

["5" to switch to slot 5]

["R" to load a new RWTS module]
  --> At $B8, load "RWTS" from drive 1

["6" to switch to slot 6]

["C" to convert disk]

                 --v--

ADVANCED DEMUFFIN 1.5    (C) 1983, 2014
ORIGINAL BY THE STACK    UPDATES BY 4AM
=======PRESS ANY KEY TO CONTINUE=======
TRK:...................................
+.5:
    0123456789ABCDEF0123456789ABCDEF012
SC0:...................................
SC1:...................................
SC2:...................................
SC3:...................................
SC4:...................................
SC5:...................................
SC6:...................................
SC7:...................................
SC8:...................................
SC9:...................................
SCA:...................................
SCB:...................................
SCC:...................................
SCD:...................................
SCE:...................................
SCF:...................................
=======================================
16SC $00,$00-$22,$0F BY1.0 S6,D1->S6,D2

                 --^--

]PR#5
]CATALOG,S6,D2

C1983 DSR^C#254
099 FREE

 A 093 HELLO
 T 002 S WORD
 B 004 GREXPA.4000
 A 022 CROSSWORD5
 T 066 TOP-TEN
 T 067 PREPOSITIONS
 T 066 WORDS
 B 023 TITLES.LNK
 B 011 STEX
 B 017 BOARDS.LNK
 A 090 CATALINK.3
 A 124 WB
 T 067 CONTRACTIONS
 B 034 BLANK
 A 067 KEYBOARD
 T 069 HOMONYMS
 T 068 COLORS
 T 067 PRONOUNS
 T 068 VERBS/IRREGULAR
 B 008 TBL
 B 030 HRCG2.ABS
 T 067 GAMES
 T 068 WORDS/COMPUTER
 T 068 TRANSPORTATION
 T 069 FOOTBALL
 T 068 STUDIES
 T 068 CLOTHING
 A 023 CROSSWORD5.UNC
 B 003 MUSIC
 B 002 MSC.LNK
 B 010 HRCG
 B 002 STS.OBJ0
 B 003 HREW5.OBJ0
 T 066 STAKE

]BRUN STEX
...works...

[S6,D1=demuffin'd copy]

]PR#6
...grinds then crashes...

My demuffin'd copy can not read itself,
because it's still looking for the non-
standard epilogue bytes. This is so
common, I wrote a tool to fix it for me
automatically: "Post-Demuffin Patcher".
(I am not good with names.) I included
the binary on my work disk, but you can
download the source code at
https://archive.org/details/
PostDemuffinPatcher4am

It does a lot more than just fix non-
standard epilogue bytes, but it looks
like that's the only thing this disk
needs. But let's find out!

                   ~

               Chapter 2
 In Which We Remove All Traces Of Copy
Protection Using An Automated Tool That
   I Wrote For Just Such An Occasion


[S6,D1=demuffin'd copy]
[S5,D1=my work disk]

]PR#5
]BRUN PDP

T00,S03,$91 change AA to DE
T00,S03,$9B change DE to AA
T00,S06,$AE change AA to DE
T00,S06,$B3 change DE to AA

Quod erat liberandum.

                   ~

           Acknowledgements


Many thanks to LoGo for supplying the
the original floppy disk.

---------------------------------------
A 4am crack                     No. 675
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