On 04/29/2012 04:48 AM, Dave Ketchum wrote:
Computers do well at performing the tasks they are properly told to
perform - better than humans given the same directions. Thus it would
make sense to direct the computers and expect them to do what is needed
accurately.
Still, we sometimes wonder exactly what the computers have been told to do.
I keep remembering a case where it took me some studying to sort out how
a computer program seemed to perform magic:
Got a diskette and was told it could not be copied - because the owner
of the program wanted to get paid for each new diskette the program was
copied to.
Curious, though not intending theft, I copied all the records to another
diskette and tried running it.
New diskette knew it was not an original, and refused to run. Looked at
records on the diskette - there were no instructions in the copied
records to do such a test - anyway, presumably the records had been
copied accurately, so their content could not indicate this was a copy.
Look more carefully - there was an odd collection of odd words. Turns
out that, when it was time to check, this collection became instructions
to look at the noise next to a particular record on the diskette and see
if the "password" was there, as it would be on the original. After
making the test, put those instructions back into their hidden form.
Ah, copy protection. They've come a long way since then: the most
difficult programs to reverse engineer now uses virtual machines with
purpose-made machine code for "processors" that don't exist outside of
the VM. The people who craft protection schemes know that it ultimately
comes down to "jump here if you've been good / if you've been bad", so
they try to bury that under layers and layers of obfuscation.
I digress :-) But this is something I've become familiar with, so I just
thought I should say it.
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