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45 lines
1.9 KiB
Plaintext
45 lines
1.9 KiB
Plaintext
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This unhappy item appeared recently on a pirate BBS:
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---------------------------------------------------------------------
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MSG LEFT BY: RESET VECTOR
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DATE POSTED: MON OCT 29 1984 7:53:45 PM
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INFOCOM HAS GOTTEN A LITTLE SMARTER ON THEIR PROTECTION, AND
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CUTTHROATS WAS PROTECTED WITH BAD SECTORS, BUT A LITTLE SNOOPING
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WITH MIDIBUG PRODUCED THE FOLLOWING CRACK:
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COPY DISK WITH BLOCKSMITH
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USE BLOCK EDIT ON BLOCK 44 AND CHANGE BYTE 15D FROM 67 TO 60
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IT'S CRACKED!
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COURTESY OF RESET VECTOR, THE POSTMEN, MACDIVISION
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WE DELIVER!
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---------------------------------------------------------------------
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This bulletin board lists similar patches to protected software from
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several dozen other companies. Though all this software is for the Macintosh,
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the method being used to break it could apply to any micro with protected
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software. Thus, any of us who do copy-protection should be aware of it.
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DESCRIPTION OF THE "CODE-PATCHING" METHOD
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Code patching will generally alter the ZIP to ignore or bypass any
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copy-protection it may be using. It works if the protected section of the
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disk contains nothing critical to the rest of the program. (This suggests
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how to defeat it, see below.)
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In Mac disks, for example, the protected section contains data which
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is checked for certain values, then discarded. The ZIP reads the protected
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section and checks for those values, returning a simple TRUE or FALSE.
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The patch listed above mungs the ZIP to ignore the check result and return
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an unconditional TRUE.
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DEFEATING THE "CODE-PATCHING" METHOD
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Code patching will fail if the contents of the protected section can't
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be ignored. Thus, protect part of the game code or the ZIP itself.
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Because the game code is subject to normal paging and $VERIFY operations,
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it's probably easier to extract and protect some chunk of the ZIP. The
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copy-protection check will then repair the ZIP's core image at boot time.
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