Cryptography Reference
In-Depth Information
could ever create.
Father and son embrace in a happy ending unspoiled by confusion or
misdirection.
14.2 Spreading the Information
Many of the algorithms in this topic evolved during the modern dig-
ital era where bits are bits, zeros are zeros and ones are ones. The
tools and the solutions all assume that the information is going to be
encoded as streams of binary digits. Tuning the applications to this
narrow view of the world is important because binary numbers are
the best that the modern machines can do. They are still capable of
hair-splitting precision, but they do it by approximating the numbers
with a great deal of bits.
The algorithms in this chapter take a slightly different approach.
While the information is still encoded as ones or zeros, the theory
involves a more continuous style. The information at each location
can vary by small amounts that may be fractions like
993
.
This detail is eventually eliminated by rounding them off, but the
theory embraces these fractional values.
This is largely because the algorithms imitate an entire collec-
tion of techniques created by radio engineers. Radio engineers at-
tacked a similar problem of hiding information in the past when
they developed spread-spectrum radio using largely analog ideas.
In the beginning, radios broadcast by pumping power in and out of
their antenna at a set frequency. The signal was encoded by chang-
ing this power ever so slightly. Amplitude modulated radios (AM)
changed the strength of signal while frequency modulated radios
(FM) tweaked the speed of the signal a slight amount. To use the
radio engineers words, all of the “energy” was concentrated at one
frequency.
spread-spectrum radio turned this notion on its head. Instead of
using one frequency, it used several. All of the energy was distributed
over a large number of frequencies— a feat that managed to make
radio communication more secret, more reliable, more efficient and
less susceptible to jamming. If the signal lived on many different fre-
quencies, it was much less likely that either intentional or uninten-
tional interference would knock out the signal. Several radios could
also share the same group of frequencies without interfering. Well,
they might interfere slightly, but a small amount wouldn't disrupt the
communications.
Many of the techniques from the spread-spectrum radio world
are quite relevant today in digital steganography. The ideas work well
.
042
or
1
.
