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A Brief History
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Modern Era | Why
is this imprtant?
The need to transfer information
has been around for a long time and does not necessarily have to
relate to computers, which is how we think about encryption and
coding today. Simply put, encryption is: scrambling data in a way
that only an authorized person (the intended recipient, hopefully)
can unscramble it. There is a small distinction that needs to be
made between the idea of hiding or concealing a message and the
idea of encoding a message. A code is rearranging the letters in
a word or the words in a sentence, where as concealing a message
is just that, using means such as invisible ink (which will be discussed
later).
These are some examples of the
concealment methods that were first used. The first one is the Scytale.
According to The History
of Cryptography Spartan generals used it during military campaigns.
It is a long, slender cylinder, or dowel, and it began with a thin
paper strip that was wrapped around it. The messages were written
along the length of the paper strip on the cylinder. After the paper
was unwrapped, the message could only be clearly read by wrapping
the paper around another cylinder of the same dimensions. Couriers
hid these paper strips in (or sometimes as) their belts or sashes.
Another, slightly more obscure
example is tattooing. According to The
History
of Encryption during the 5th century B.C., a Greek serving in
the Persian court sent a message back to Greece calling for an assassination.
The message was tattooed onto the scalp of a trusted slave. The
message was covered by his hair, which had since grown back. This
sort of method continued to be used as recently as WWI when agents
were sent across enemy lines with messages written onto their skin
in "invisible ink." This "invisible
ink" was really milk, fruit juice, or even urine, which darken
when heated, causing the message to "reappear."
The idea of language
itself being used to send coded messages was used during WWII. Messages
were sent via a little known language, Navajo. The language was
unknown to interceptors, so they were not able to deduce the content.
Another example mentioned by Professor Markham is the cockney rhyming
slang, using rhymed words to stand for other words "lid"
"kid" for example.
Now for another distinction,
this time between codes and ciphers. A code generally replaces an
entire word, while a cipher replaces the individual letters. Cipher
literally means "to number." Most are systematic in nature,
often making use of mathematical number techniques and formulas.
It replaces the individual letters in a message with different letters
or symbols and they require a key to solve. A very simple example
is known as the Caesar Cipher, where each letter is replaced with
the letter that followed it alphabetically by 3 places, so an A
would be a D and a B would be an E and so forth. Another example
is the grid cipher. The grid coordinates are used to substitute
for each letter in a message. 3-4, 4-3, 3-4 would be S-O-S. Altering
the patterns of letters in the matrix can change the cipher.
Modern Era
Enigma Cipher
The Enigma
Cipher Machine was invented by the Germans in World War II (1918)
to aid in the transmission of coded messages. It was based on a
system of three rotors that substituted plain text for coded letters.
The rotors would spin in synchrony with the others to produce shifts
similar to the Cesar Shift. For example, as a letter was typed on
the keyboard of the machine, it would pass through the three rotors
to create a substituted letter. This process allowed 17,576 possible
positions of the rotors. A particular letter would not be coded
as the same letter twice. ("B" could be an "m",
or a "k", or an "l"- depending on the position
of the rotors)
Since the settings were changed
on a daily basis the receiver (of the message) needed to know the
initial settings of the rotors to decipher the code. This security
feature put interceptors at a disadvantage because they were probably
too late in attaining and transmitting the code through the Enigma
Cipher. However, that did not stop them. As a consequence, the bombe
computer was developed to crack the German encryption machine.
One Time Pad
The development of the bombe
computer should not be interpreted as a failure of encryption because
it contributed to the development of the One
Time Pad. This new form of encryption was based on the idea
that a key, as long as the text, was used to filter the original
message to produce a coded message. What makes it so different?
Well, the Enigma Cipher was based on the same concept only that
it filtered the message letter by letter.
The most important security
measure was the use of a truly random filter to encode the message.
Similar to the German encryption machine, the One Time Pad produced
random data for every text message, so that the letter "a"
would unlikely be coded as an "m" every time it appeared
in a message. To decode the message the receiver had to be given
the original key used to encrypt the message.
Public Key Cryptography-Asymmetric and Symmetric
Ciphers (1970's)
You may be questioning yourself
about what these things are. Let us explain. Despite the breakthrough
of the One Time Pad, encryption still proved to be vulnerable to
interceptive attack. A major drawback was finding a way to securely
exchange a key over insecure lines. A solution was proposed! Whitfield
Diffie, Martin Hellman, and Ralph Merkle examined the problem of
key exchange and fortunately Hellman made his breakthrough (Draper).
He proposed the idea of having both a public and a private key.
The public key would serve to encrypt messages and the private key
would decrypt messages. This became known as an asymmetric
cipher (Draper). Prior to this advancement, cryptography
keys (or ciphers) had been symmetric.
This meant that in order to crack the code the recipient had to
reverse the function that encrypted it (Draper). This method has
been termed Public Key Cryptography and
is considered to be one of the most advanced technological innovations
in the field of cryptographic technology.
Steganography
Steganography, is widely thought
to have been a method used in planning recent terrorist events,
as you guys read in the articles. According to Cristobal
the word literally means "covered writing" and it is the
art and science of communicating which hides the existence of communication.
Its purpose is to convey a message to a receiver in such a way that
the presence of the message is undetectable by a third party. In
the computer world, it means hiding secret messages in graphics,
pictures, movies or sound.
A pre-existing image is used
as a "container." Computer images are composed of pixels
and one way to represent a pixel is with a numerical value. An 8-bit
number represents the value to the computer. The eighth digit in
the sequence, the one farthest to the right is called the least
significant bit. This is the number that is changed by someone wishing
to hide a message. The reason the image itself isn't altered is
because the 7 bits that remain unchanged contain enough information
to establish the correct pixel color of the original image, and
the picture still looks the same. Think of a bag of red jellybeans,
if you replace one red jellybean with a pink jellybean, at a distance
you cannot tell, they all just look red.
Why is This Information Important?
It is obvious
how quickly technological advances in Cryptography develop. Some
scholars will argue that encryption provides a security so tight
that is "virtually" impossible to break (Draper). Others
will refute that 100 % security does not exist.
As we have witnessed, the bombe
computer cracked the enigma machine. This led to the development
of the one time pad, which stood with many of its flaws to be corrected.
It seems as though there was always a constant struggle to determine
what was more efficient or secure. I do believe the same principle
stands today. Technology and communication are both fields undergoing
constant motion and development.
Since encryption may have played
a role in the World Trade Center attack it is extremely important
for us to develop a sense of knowledge about what may have helped
facilitate such a horrendous event. We may not have felt its direct
repercussions but I do believe that it has put our minds to work.
These frightful acts have caused a sense of apprehension about what
to expect. So I leave you with a thought to ponder about, how beneficial
is technology?
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