I looked into this area a while ago, doing some cracking of my own purely
for "educational" purposes. You'd be surprised how much a then newbie coder
can do with a few hacking faq's and howto's.
It seems no one method will fix it on its own, and if someone is determined
enough they will crack your program. However, that is no excuse to make it
easy for them. The three checks I would make are:
1. File size, check a number of times throughout your program the file
sizes. Do it in a number of places so that disabling it is difficult. If you
can't bypass the file size checking, cracking becomes a whole lot more
difficult.
2. As I think Nahum suggested, call the registration key with a bad code
expecting a false return. Do it a number of times in your code, without
calling one function. This really screws with crackers minds.
3. Don't leave obvious strings lying around in the executable such as
"Please enter your registration code" or other important constants. Try
searching a standard executable, you'd be surprised how easy it is to find
them. Instead encode them so they look like binary, ie add 100 to the Ascii
value, then decode it at run time.
The idea is to make the hackers work hard, consider it a game, if you don't
win first time
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Nahum Wild
Sent: Friday, 13 August 1999 12:29
To: Multiple recipients of list offtopic
Subject: RE: [DUG-OFFTOPIC]: Cracks
> Not really... you can do a search for the setup code used to generate the
call to
> the authentication routine... Once it lights up 30 or so located - the
hacker's
> gonna get real busy circumnavigating the code inside the routine rather
than the code
> calling the routine...
But if you have a check by sending a bad regcode to the authentication
routine expecting it to return false then you catch the case of 'someone has
circumnavigated the code inside the routine making it return true all the
time'. Don't you? That would be the hope anyway.
Nahum
-----Original Message-----
From: Aaron Scott-Boddendijk [mailto:[EMAIL PROTECTED]]
Sent: Friday, 13 August 1999 10:46
To: Multiple recipients of list offtopic
Subject: Re: [DUG-OFFTOPIC]: Cracks
> This MIGHT be a good thing in some ways. IF you just have a generic
routien
> that you call to check if reg. or not, and do it in heaps of places, then
> the cracker is likly to get board and give up, not cos. its too
complicated,
> but cos there would be some many place.
> They wouldn't ness. know this straight awat either...
Not really... you can do a search for the setup code used to generate the
call to
the authentication routine... Once it lights up 30 or so located - the
hacker's
gonna get real busy circumnavigating the code inside the routine rather than
the code
calling the routine... Also never call your authentication code directly -
always use a
function pointer and have each module carry it's own copy of the function
pointer.
Add a couple of dummy parameters so that the search for call setup code
isn't
consistent and therefore hard to spot. Use several types of authentication
such as
code verification, CRC checks, file-date stamping.
--
Aaron Scott-Boddendijk
Jump Productions
(07) 838-3371 Voice
(07) 838-3372 Fax
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