Cryptography Reference
In-Depth Information
period to the other happened through a kind of break, of qualitative jump, which
enabled cryptologists to break free of the mechanical and conceptual constraints
which limited the blossoming of their art.
4
My purpose in this chapter is to provide a different account of the his-
torical evolution of cryptography—one that challenges an evolutionary
narrative that is perhaps a little too clean, perhaps a little too predictable.
Most important, this account questions the premise that the digital repre-
sents the final stage of a long struggle for information to emancipate itself
from the shackles of materiality, from the “mechanical constraints” that
had previously limited its potential. It is one argument of this topic that
the tendency to conceptualize digital information as immaterial has mar-
ginalized important dimensions of cryptographic theory and practice.
These repressed dimensions have now become recurrent stumbling blocks
for the fulfillment of the cryptographic community's scientific and social
aspirations.
In fact, cryptography's formal disengagement with the material dimen-
sion of information is a contemporary phenomenon. For much of its
history, cryptographers had recourses to methods for
hiding information
just
as much as they had to ciphers. Such methods involve the creative dis-
simulation of one signal within another—for example, embedding Morse
code in an ordinary document using the dots of the
i
s and
j
s and the dashes
of
f
s and
t
fs Rather than direct attack on the technical characteristics of
the mechanisms themselves, it is also through such material properties
that the effectiveness of many cryptographic schemes is often subverted.
In the previous century, for example, as the quantity of encrypted military
communications grew, methods of
traffic analysis
extracted considerable
intelligence from mere communication patterns, even if the content of
those communications remained inaccessible. Whether as marks on papers
or radio waves, the physical embodiment of cryptographic mechanisms
thus provides both resources and threats for the accomplishment of secu-
rity goals. As I shall explore in chapter 7, computerization has only exac-
erbated this state of affairs.
In this chapter, I read the history of cryptography as it unfolds together
with the various technologies that have successively dominated (military)
communications—namely paper, telegraph, radio, electromechanical
devices, and networked digital computers. Given that David Kahn's author-
itative survey,
The Codebreakers
, comes in at just under 1200 pages, the goal
