Computer World. Матросова Т.А. - 104 стр.

UptoLike

ВУЗ: 

УлГТУ | Ульяновск

Составители: 

Рубрика: 

103
In modern times, cryptography's main role has been in securing electronic
communications, moon after Samuel F. B, Morse publicly demonstrated the telegraph
in 1845, users of the telegraph began worrying about the confidentiality of the
messages that were being transmitted. What would happen if somebody tapped the
telegraph line? What would prevent unscrupulous telegraph operators from keeping a
copy of the messages that they relayed and then divulging them to others? The
answer was to encode the messages with a secret code, so that nobody but the
intended recipient could decrypt them.
Cryptography became even more important with the invention of radio, and its
use in war. Without cryptography, messages transmitted to or from the front lines
could easily be intercepted by the enemy.
Code Mak ing and Code Bre ak ing
As long as there have been code makers, there have been code breakers. Indeed,
the two have been locked in a competition for centuries, with each advance on one
side being matched by counter-advances on the other.
For people who use codes, the code-breaking efforts of cryptanalysts pose a
danger that is potentially larger than the danger of not using cryptography in the first
place. Without cryptography, you might be reluctant to send sensitive information
through the mail, across a telex, or by radio. But if you think that you have a secure
channel of communication, then you might use it to transmit secrets that should not
be widely revealed.
For this reason, cryptographers and organizations that use cryptography
routinely conduct their own code-breaking efforts to make sure that their codes are
resistant to attack. The findings of these self-inflicted intrusions are not always
pleasant. The following brief story from a 1943 book on cryptography demonstrates
this point quite nicely.
The importance of the part played by cryptographers in military operations was
demonstrated to us realistically in the First World War. One instructive incident
occurred in September 1918, on the eve of the great offensive against Saint-Mihiel. A
student cryptographer, fresh from Washington, arrived at United States Headquarters
at the front. Promptly he threw the General Staff into a state of alarm by decrypting
with comparative ease a secret radio message intercepted in the American sector.
The smashing of the German salient at Saint-Mihiel was one of the most
gigantic tasks undertaken by the American forces during the war. For years that
salient had stabbed into the Allied lines, cutting important railways and
communication lines. Its lines of defense were thought to be virtually impregnable.
But for several months the Americans had been making secret preparations for
attacking it and wiping it out. The state was set, the minutest details of strategy had
been determined – when the young officer of the United States Military Intelligence
spread consternation through our General Staff.
The dismay at Headquarters was not caused by any new information about the
strength of the enemy forces, but by the realization that the Germans must know as
much about our secret plans as we did ourselves – even the exact hour set for the

Страницы