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June 14, 2004
A: FROM STUDENT MEMBER SARAH U-M IN CA
All encryption algorithms require one or more "keys"--
user-inputted strings of data. Key length is usually
measured in bits (a bit is a single 1 or 0). The
larger the key length, the greater the number of
possible values for the key, called the "keyspace".
Every bit added doubles the keyspace.
The goal in creating an algorithm is to somehow make
it so no information can be deduced from the
ciphertext alone. (Kerckhoff's principle: "the
security of a cryptosystem should depend only on the
secrecy of the key.") Thus, the best way an enemy has
to decipher an intercepted message is to try every
key, one by one. This is known as a "brute-force
attack". The larger the keyspace in an ideal
cryptosystem, the longer a message will take to
decipher.
From a simplistic point of view, computers have simply
sped up the key-checking process. I'm more interested
in the mathematics than the history of
cryptography/cryptanalysis, but I believe the first
machines designed for breaking ciphers were the
"bombes" used by Turing and Welchman at Bletchley
Park
in WW II. I'll second Ms. Kane-- Alan Turing rocks....
I don't know too much about computing pi. I believe
the same result occurs: basically, computers make
calculating a lot faster. Google should have all you
need to know.
I could babble on about finding primes and the
difference between public and private keys for longer
than even the mentors would want to listen, so I'll
stop here. It's awesome that you're interested in
this: there are so few female crypto enthusiasts I
know of and none are my age. I'd love to chat sometime
with anyone who's interested. Check out sci.crypt for
a good time.
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June 11, 2004
A: FROM MENTOR LORI KANE IN
MA
Computers have brought us from ancient times, where ciphers
were as simple
as substituting one letter for another, to technology such
as the Enigma,
which was an electro-magnetic machine used by the Germans
in the second
World War, to the electronic forms we have today. Today we
mostly use two
kinds of encryption: public and private key cryptography (and
the key
systems that you've probably heard of: DES, RSA, etc.). This
technology
encrypts information using an algorithm that is computationally
difficult
to solve (within a practical amount of time) without having
the key.
One of the most important code breakers in history is Britain's
Alan
Turing. He is considered one of the founders of code breaking
and computer
science. Turing is most famous for cracking the Enigma cipher
machine
which greatly helped the Allies win the battle of the Atlantic
and
eventually the war. You can read about his fascinating life
and tragic end
on the following sites:
http://www.turing.org.uk/turing/
http://www.alanturing.net/turing_archive/
Here are other good sites for information on cryptography:
http://www.busan.edu/~nic/networking/puis/ch06_01.htm
http://www.vectorsite.net/ttcode.html
The Code Book by Simon Singh is also a great source on the
history of
cryptography (and can be found at most book stores).
...I'll have to let one of the other mentors talk about pattern
finding.
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