Cryptography Reference
In-Depth Information
seemingly primitive technology, nomenclators, ruled the cryptographic
world longer than any other technique, but could not be adapted to the
military requirements of the Civil War, while commercial codes provided
“good enough privacy” for business use. The effectiveness of any crypto-
graphic method can only be evaluated based on careful evaluation of the
totality of such factors rather than mere mathematical strength.
Cryptography Is Brittle and Key Distribution Difficult
Large-scale deployment of cryptographic systems, mostly observed in the
context of warfare, demonstrates the enormous practical difficulties in ens-
uring their proper functioning. In particular, procedures for key distribu-
tion, while integral to the security of these systems, must be precisely
adhered to. As a result, the practice of cryptography demands rigorous
discipline, rarely met even by trained operators. Cryptanalysis thus some-
times proceeds by direct attack on the mathematical properties of ciphers,
but mostly thrives on inevitable procedural errors. This is in part due to the
structural contradiction between the demand for systematic production of
randomness
in cryptographic procedures and cognitive needs of crypto-
graphic operators to
routinize
their behaviors, whether motivated by pro-
ductivity or fatigue. As Kerckhoffs's desiderata highlighted as early as 1883,
in cryptographic design, “easy” and “secure” exist in a space of constant
trade-offs.
Cryptography Is a Material and Embodied Activity
Cryptography cannot hide the very existence of a message, which com-
municates the desire for secrecy. Traffic analysis reveals the origin, destina-
tion, and size of messages, as well as overall communication patterns. A
Morse operator's “fist” is embedded in a radio signal. Computing and com-
munication always occur through some kind of material means, and—as
subsequent chapters will explore—the material basis of modern networked
computing offers new resources and challenges to cryptographic algo-
rithms. Steganography and cryptography thus exist in a more symbiotic
relationship than modern taxonomies of the field have allowed for.
Certainty Is Elusive
Cryptographic knowledge seems to constantly oscillate between the three
states succinctly articulated by Donald Rumsfeld in 2002 in a press confer-
