Cryptography Reference
In-Depth Information
your life and putting bad relationships behind you is an
even better cure for the human heart. That's the message
I think that is encoded in those three-point shots.
CM:
We're back from the time out now. Let's see what the Shot
Shooters can do.
PBPM:
The Shot Shooters put the ball in play. Carter pauses and
then passes the ball over halfcourt to Martin. He fakes
left, goes right. It's a wide open lane. He's up and bam,
bam, bam. That's quite a dunk. The Passmakers didn't
even have a defense.
CM:
Whoa. That sends a message right there. A dunk like
that just screams, “You think three-point shots scare me?
You think I care about your prissy little passing and your
bouncy jump shots? There was no question where this
ball was going. Nobody in the stands held their breath to
see if it would go in. There was no pregnant pause, no
hush sweeping the crowd, and no dramatic tension. This
ball's destiny was the net and there was no question about
it.” He's not being steganographic at all.
15.2 Created Worlds
Many of the algorithms for sound and image files revolve around
hiding information in the noise. Digitized versions of the real world
often have some extra entropy waiting for a signal. But advances in
computer graphics and synthesis mean that the images and sound
often began life in the computer itself. They were not born of the
real world and all of the natural entropy constantly oozing from the
plants, the light, the animals, the decay, the growth, the erosion, the
wind, the rain and who knows what else. Synthetic worlds are, by
definition, perfect.
At first glance, perfection is not good for hiding information.
Purely synthetic images began as mathematics and this means that a
mathematician can find equations to model that world. A synthetic
image of a ball in the light has a perfect gradient with none of the dis-
tortions that might be found in an image of an imperfect ball made
by worn machinery and lit by a mass-produced bulb powered by an
overtaxed electrical system.
These regularities make it easy for steganalysis to identify images
with extra, hidden information. Even slight changes to the least sig-
nificant bit become detectable. The only advantage is that the in-
creasing complexity of the models means that any detection pro-
cess must also become increasingly complex too. This does pro-
