Re: Clever ways to hide a compare

I did say if you are using DOS. This won't work for Windows NT unless you
know a lot about the internals of the kernel and then even self modifying
code is possible with device driver support. How can you have a buffer
overflow if you write the code correctly. You are setting things based upon
decisions you have made and not on user input. It might be a side effect of
user input in that you might change the code flow based upon that input, but
you will have checked and validated the input before you start making these
type of modifications.

"Aslan" <spamtrap@xxxxxxxxxx> wrote in message
news:1127634980.916261.122630@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> David J. Craig yazdi:
>> Depending upon the register/data size, you can use a subtract, add,
>> multiply, or divide. You can do a translate and come up with some
>> interesting possibilities. If this is DOS and not Windows NT, you can
>> have
>> self modifying code that can do wonderful things. Translate an
>> instruction
>
> Isn't is possible under Windows NT? How 'bout a buffer overflow attack
> against your code on purpose? Is it a good idea or bad idea?
>
>> to something good if the value is good. Otherwise change it to something
>> that will lead to headaches.
>>
>> "jonathon" <spamtrap@xxxxxxxxxx> wrote in message
>> news:1127603005.082317.85010@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> >
>> > Suppose you are writing a protection scheme, and need to compare 2
>> > values. Is there a clever way to do this without an outright 'cmp'
>> > instruction? Of course it's always possible to use the value in a
>> > calculation that is needed for correct functionality of the program,
>> > but I was wondering if there is a way to have 2 values compared in a
>> > sneaky way where it is not immediately evident what is happening.
>> >
>


.

Relevant Pages

  • Re: which way is faster?
    ... Then we can compare the framerate. ... I never heard of speed comparisons between dos and windows. ... No theoretical reason you couldn't do it from dos, but you'd need a routine to detect what card you had, and routines to implement hardware acceleration for as many cards as you'd like to support. ...
    (alt.lang.asm)
  • Re: Clever ways to hide a compare
    ... > decisions you have made and not on user input. ... >> David J. Craig yazdi: ... If this is DOS and not Windows NT, ...
    (comp.lang.asm.x86)
  • JOptionPane
    ... i do a simple program which runs in Dos. ... When user input a keyword, ... dialog box will pop up but it hides behind all the windows forms i have ...
    (comp.lang.java.programmer)
  • Re: Clever ways to hide a compare
    ... > I did say if you are using DOS. ... This won't work for Windows NT ... It might be a side effect of user input in that you might ... You can do self modifying code on NT without any problems, ...
    (comp.lang.asm.x86)
  • ~~~~~~~~~~~~~~ FILE NAME ~~~~~~~~~~~~~~
    ... adapter description file file name extension ... apple script to change file names ... batching file name changes in windows ... change short file names in dos ...
    (sci.misc)