Cryptography Reference
In-Depth Information
to equate this phase with the appearance of public-key
cryptography, but that is too narrow a view. Cryptology's
third phase was the inevitable consequence of having to
devise ways for electronic information to perform all of
the functions that had historically been done with the aid
of tangible documents.
The impacT of elecTronics
In the years immediately following World War II, the
electronic technology developed in support of radar and
the recently discovered digital computer was adapted to
cryptomachines. The first such devices were little more
than rotor machines in which rotors had been replaced
by electronically realized substitutions. The advantage
of these electronic machines was speed of operation; the
disadvantages were the cryptanalytic weaknesses inher-
ited from mechanical rotor machines and the principle of
cyclically shifting simple substitutions for realizing more
complex product substitutions. In fact, rotor machines
and electronic machines coexisted into the 1970s and
early '80s. There is little information in the open literature
about the electronic cipher machines used by the various
national cryptologic services, so the most reliable indica-
tion of cryptographic developments in the period from
the final generation of rotor machines—the KL-7 devel-
oped by the United States for the North Atlantic Treaty
Organization (NATO)—to the appearance of DES and
public-key systems in 1976 is to be found in commercial
equipment. (The KL-7 was withdrawn from service in
June 1983; in 1985 it was learned that the Walker family spy
ring had turned over a KL-7 device and keying material to
the Soviets.)
