Cryptography Reference
In-Depth Information
Figure 10.6: The NSA's 50th Anniversary Exhibit.
This exhibit is in the NSA's National CryptologicMu-
seum, and is courtesy of the NSA. For more details see
http://www.nsa.gov/museum/museu00021.cfm
.
For more than half a century the NSA has been at the forefront of high-
tech development including paving the way for the first large-scale computer,
the first solid-state computer, the tape cassette, and modern semiconductor
10.39
technology. The NSA also employs certainly the largest number of mathemati-
cians in the United States, and arguably, in the world. Their cryptologists and
mathematicians help the agency to design ciphers and find deficiencies in enemy
cryptosystems.
In other words, their job is to make and break codes. In the NSA, this is
10.39
A
semiconductor
is a substance that selectively conducts electricity through the move-
ment of electrons and
holes
(which are electric charge carriers with positive charge, equal in
magnitude, but opposite in polarity to the charge of an electron). A semiconductor is interme-
diate between conductors (like copper that freely conducts electricity), and insulators (such
as rubber, which does not conduct an electrical charge). For instance, silicon is a semicon-
ductor, and usually microchips (sometimes called simply
chips
or
integrated circuits
(IC)s),
are fabricated on semiconductor substances such as silicon. The substance,
silicon
, present in
glass and sand, for instance, is the best known semiconductor material for electronic compo-
nents. Silicon will conduct electricity in a fashion depending upon the impurities added to it,
called
doping
. If the addition of impurities causes the majority of the charge carriers to be
negatively charged electrons, then this is called
N-type silicon
. If addition of impurities leads
to the majority of charge carriers being positively charged holes, then we have
P-type silicon
.
Typically silicon material used in electronics has both N- and P- type material.
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