Computer World. Матросова Т.А. - 105 стр.

UptoLike

ВУЗ: 

УлГТУ | Ульяновск

Составители: 

Рубрика: 

104
attack. The intercepted message had been from our own base. German cryptographers
were as expert as any in the world, and what had been done by an American student
cryptographer could surely have been done by German specialists.
The revelation was even more bitter because the cipher the young officer had
broken, without any knowledge of the system, was considered absolutely safe and
had long been used for most important and secret communications.
Cryptography and Digital Computers
Modern digital computers are, in some senses, the creations of cryptography.
Some of the first digital computers were built by the Allies to break messages that
had been encrypted by the Germans with electromechanical encrypting machines.
Code breaking is usually a much harder problem than code making; after the
Germans switched codes, the Allies often took several months to discover the new
coding systems. Nevertheless, the codes were broken, and many historians say that
World War II was shortened by at least a year as a result.
Things really picked up when computers were turned to the task of code making.
Before computers, all of cryptography was limited to two basic techniques:
transposition, or rearranging the order of letters in a message (such as the Spartan's
scytale), and substitution, or replacing one letter with another one. The most
sophisticated pre-computer cipher used five or six transposition or substitution
operations, but rarely more.
With the coming of computers, ciphers could be built from dozens, hundreds, or
thousands of complex operations, and yet could still enc rypt and decrypt messages in
a short amount of time. Computers have also opened up the possibility of using
complex algebraic operations to encrypt messages. All of these advantages have had
a profound impact on cryptography.
Modern Controversy
In recent years, encryption has gone from being an arcane science and the stuff
of James Bond movies, to being the subject of debate in several nations (but we'll
focus on the case in the U.S. in the next few paragraphs). In the U.S. that debate is
playing itself out on the front pages of newspapers such as The New York Times and
the San Jose Mercury News
On one side of the debate are a large number of computer professionals, civil
libertarians, and perhaps a majority of the American public, who are rightly
concerned about their privacy and the secrecy of their communications. These people
want the right and the ability to protect their data with the most powerful encryption
systems possible.
On the other side of the debate are the United States Government, members of
the nation's law enforcement and intelligence communities, and (apparently) a small
number of computer professionals, who argue that the use of cryptography should be
limited because it can be used to hide illegal activities from authorized wiretaps and
electronic searches.

Страницы