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The concept of coding information
has been around for a very long time.
Various methods have been used at various
times.
Methods
The substitution method, which was made
popular by secret decoder rings, was one
early approach. It worked - somewhat - but
in the modern computer age it wouldn't last
a minute.
In the old days, you could simply use a
language that the "other side" didn’t know.
But nowadays, that won’t work, since
everyone has access to all the languages
through computers and the Internet.
AltaVista's Babel Fish, anyone?
Using a book or well-known document and
picking words or letters from it works quite
well, if the source you pick from is not
well known and both parties have it. The
flaw in this method is that if you try for a
wide distribution and some of your people
get caught, the "enemy" can see which books
they have in common - and there goes your
code.
The most popular method of coding messages
now is encryption - basically assigning each
symbol you use a number, then transcribing
the message to numbers, and then performing
some sort of mathematical operation on the
numbers, using a "key" as the other
variable.
The very early encryptions failed when
computers became fast enough to do the grunt
work and just gave humans the best results
to look at and tweak.
But today encryption can be nearly
fool-proof, if you use a good key.
Encryption Keys
An encryption key is a series of numbers
that are used in an equation to give you new
numbers to put in the coded message. The key
is also used to reverse that operation, and
change the numbers back into the original
letters and symbols.
The best way to make breaking an encryption
key's code harder is to make the key longer.
A longer key will use each number in the key
fewer times, which will give the code
breaker fewer characters to work with to try
to figure out each part of the key. The
ideal key will be even longer than the
message it is encoding, so each part will be
used only once per message. There is no way
to break an encryption where each part of
the key is used only once, since each
character can have any value and there is no
way to compare this character to that
character.
Here is an example of how this would work
with a key 100 numbers long and a message
20,000 characters long. Each number in the
key will be used 200 times (20,000/100 =
200). Since the number in each place in the
key never changes, the more times that
number is used, the more limited its
possible values become, and the easier it
gets to figure out what the value of the
number in the key is.
Lets say you are using only lower case
letters - no numbers or symbols - except the
space. If the third number in the key is
used to code an “a” and a “z” then the two
coded values will be 26 places apart and it
will be simple to calculate the value of the
third number in the key. So now the person
breaking the key will know every character
in the third place of 100 in the given
message.
This is a perfect match, but with 200
letters coded with the same number in the
key, most possible values for all the
numbers in the key will be eliminated. “a”,
“b”, and “y” are all fairly common letters
so in 200 letters they should occur at least
once.
That explains why an extremely long key is
nearly impossible to break - if a place in
the key is used only once, there is nothing
to compare it to, and no way to limit what
it could be.
Espionage?
Far too many people now have an active
interest in hacking computers and accessing
the files on them, including hackers,
scammers, identity thieves, and con men.
Just tune into the news and you’ll hear
stories about how many times this
corporation or that government agency got
hacked and lost copies of thousands, or even
millions, of records, many including
personal data.
Your business competitors, suppliers, and
even your customers may have an interest in
getting at your files as well. Knowing your
actual costs, the lowest prices you will
really accept, knowing what projects you are
working on, and what weakness you are
concerned with can all help them and destroy
you.
Even the government seem to have an active
interest in what is on your computer.
Carnivore was a program they used to monitor
network traffic and emails.
http://email.about.com/od/staysecureandprivate/a/carnivore.htm
Magic lantern is a program the government
used to log keystrokes. These programs
represent just a small sample of what the
government admits to having and using - who
knows what all they really have! The
government has also requested the master
keys to some of the more common encryption
programs that are available to private
citizens, and may have them - which means
that when it comes right down to it, those
programs are useless.
Summary
You need to know who might be after your
information, how they are trying to get it,
and how to protect yourself.
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