Keys - Disappearing Cryptography - page 231

burgh.“Someofusneedtofocusonthesmallthingsandthedetails
to make progress. That's the key.”
Konstantine dismissed this objection and suggested that the vi-
rologists might make more progress if they avoided a narrow focus.
“The key insight, or perhaps I should say the true vision, is that
scientists who focus too narrowly avoid seeing the big picture. We
want more big pictures. If that means abandoning the hope for one
key, so be it.”
12.2 Extending Control
Most of the game of steganography involves finding a set of algo-
rithms that can make one chunk of data look like another. In some
instances, camouflaging the existence of the data is not enough.
Stronger attacks require stronger measures and one of the most ver-
satile is adding some key bits to the algorithm.
The key is some relatively small collection of bits that plays a
strong role in the algorithm. If someone doesn't hold the right key,
they can't unlock certain features of the algorithm. The bits of infor-
mation in the key are somehow essential for manipulating the data.
Most of the keying techniques used in steganography are exten-
sions of the solutions used in basic cryptography. Some of the basic
types include:
Secret Keys One key is used to hide the information and the same
key must be available to uncover the information. This is of-
ten called symmetric or private key steganography. The second
term isn't used in this topic to avoid confusion with public-key
approaches.
Public Mechanisms or Public Keys One key hides the information
and a different key uncovers it. Some call these asymmetric be-
cause the algorithms separate the functions. These solutions
are often useful for watermarking information because some-
one can uncover the information without the power to hide
new information— that is, the power to make new copies with
the person's watermark.
None of the algorithms described here offer a solution with
any of the simplicity of the best public-key encryption systems.
They often rely on difficult problems or some obscurity to pro-
vide some form of a “private key”. In many cases, there is no
private key at all. The public key is just used to verify the signa-
ture.