-----------Math in a Nutshell----------
A 4am crack                  2015-11-06
---------------------------------------

Name: Math in a Nutshell
Genre: educational
Year: 1985
Publisher: Learning Technologies, Inc.
Media: single-sided 5.25-inch floppy
OS: Diversi-DOS (T02,S02 has the string
  "C1983 DSR" backwards)
Previous cracks: none
Identical cracks:
  #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 "HELLO"

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


]CATALOG,S6,D1

C1983 DSR^C#254
221 FREE

*A 002 HELLO
*B 005 ASMRTN2
*B 021 LITAGM
*B 013 LTIM
*A 005 JELLO
*B 071 PICPIC
*B 021 P1
*B 033 TITLE.LTI
*A 018 JAME
*B 034 CHOOSEJMP
*A 018 JAME2
*B 034 DIR

]RUN HELLO
...crashes...

[S5,D1=DOS 3.3 master disk]

]PR#5
]RUN HELLO,S6,D2
...program loads and runs...

So it doesn't like Diversi-DOS 64K (the
DOS on my work disk). It's probably
accessing DOS functions directly or
assuming the RWTS parameter table is at
specific address, instead of using the
vectors on page 3. But it works when I
boot an unmodified DOS 3.3 first, so it
isn't checking for its original DOS at
runtime.

[S6,D1=demuffin'd copy]

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

The demuffin'd disk can't read itself.
This is not unusual.

                   ~

               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

; fix epilogue byte checking in RWTS
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

Side B has identical protection.

Quod erat liberandum.

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A 4am crack                     No. 487
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