A Look at Public Key Encryptio
A Look at Public Key EncryptioA Look at Public Key Encryption
Encryption is the process of disguising information by transforming plain text into gibberish, or ciphertext, which cannot be understood by an unauthorized person. Decryption is the process of transforming ciphertext back into plaintext that can
be read by anyone. Example of encryption can be found in history,
for example in the era of the Cold War, the Solviet Union and the
United States would send electronic messages to one military
point to another, encrypted. If the enemy intercepted the
message, they would have to crack this message to get the
information. Typically when governments used encryption they used
a very complex method of encrypting messages. Encryption does not
have to be complex; the Captain Video Decoder Rings that we had
as children used encryption. You'd encode your secret message,
such as "Meet me by the swings," by replacing the letters of the
alphabet with substitute letters from a certain number of places
away. For example, let's say we decide to use the key "+4." That
would mean we'd switch each letter in our message with the letter
that comes four places later in the alphabet. D would become H; R
would become V, and so on. You, or anyone else who knows the key
can easily switch the H back to a D, the V back to an R, and
figure out where to meet. Theses two examples are on opposite
sides of the spectrum, but both have their similarities and their
differences.
The major difference complexity, the government pays
mathematicians to research complex algorithms by which to encode
the messages, like the system used by Captain Video but these
algorithms are complex enough that if you tried to crack them it
would take you decades with even the most powerful computer
today. This complex mathematical code is what makes the text
secure to anyone who tries to crack it. Some similarities we can
find in these two examples are their use of the key, the
unlocking instructions, to decode the message. They only used one
key to encrypt and decrypt the messages. This creates problems,
security problems. The single key must itself be kept very
secret, while somehow still being transmitted to the person
receiving encoded messages. Even if the key is transmitted
safely, which you can never know for certain, the recipient can
never be sure received messages haven't been intercepted by the
enemy, altered, and passed along to create havoc and disarray.
This was a major fault of the one key system that made it very
vulnerable. The answer to this problem can in 1976.
Up until 1976 no one outside the government or at least outside
the government's control, performed any serious work in
cryptography. The National Security Agency (NSA) was in charge of
all advancement of cryptography, and that changed when a 31-year-
old computer wizard named Whitfield Diffie came up with a new
system, called "public-key" cryptography.
Diffie tended a complicated multi-user computer system at
MIT. He became troubled with the problem of how to make the
system, which held a person's work and sometimes his or her
intimate secrets, truly secure. The traditional, top-down
approach to the problem- protecting the files by user passwords,
which in turn were stored in the electronic equivalent of vaults
tended by trusted system administrators- was not satisfying. The
weakness of the system was clear: The user's privacy depended on
the degree to which the administrators were willing to protect
it. Diffie recognized that the solution rested in a decentralized
system in which each person held the literal key to his or her
own privacy. He tried to get people interested in taking on the
mathematical challenge of discovering such a system, but there
were no takers. It was not until the early 1970s, when the people
running the ARPAnet were exploring security options for their
members, that Diffie decided to take it on himself. By then he
was at Stanford, under the thrall of David Kahn's work. The
problem with the existing system of cryptography was that secure
information traveled over insecure channels. In other words, a
message could be intercepted before reaching its recipient. The
passing of the key Kahn realized also was a major problem. The
problem got even worse when one tried to imagine encryption
employed on a massive scale. The only way to do it, really, was
to have registries, or digital repositories, where keys would be
stored. As far as Kiffie was concerned, that system was screwed,
you wound up having to trust the people in charge of the
registry. It negated the very essence of cryptography, to
maintain total privacy over your own communications.
In May 1976, collaborating with Stanford computer scientist
Martin Hellman, Diffie cracked both problems. His scheme was
called public-key cryptography. It was a brilliant breakthrough.
Every user in the system has two keys - a public key and a
private key. The public key can be widely distributed without
compromising security; the private key, however, is held more
closely than an ATM password- you don't let anyone get at it. For
relatively secret mathematical reasons, a message encoded with
either key can be decoded with the other. For instance, if I want
to send you a secure letter, I encrypt it with your public key
(which I received from you), and send you the ciphertext. You
decipher it using your private key. Likewise, if you send a
message to me, you can encrypt it with my public key, and I'll
switch it back to plaintext with my private key.
This principle can also be used for authentication. Only one
person can encrypt text with my private key-me. If you can decode
a message with my public key, you know beyond a doubt that it's
straight from my machine to yours. The message bears my digital
signature.
By 1977, three members of this new community created a set
of algorithms that implemented the Diffie-Hellman scheme. Called
RSA for its founders - MIT scientists Rivest, Shamir, and Adleman-
it offered encryption that was likely to be stronger than the
Data Encryption Standard (DES), a government- approved
alternative that does not use public keys. The DES system is
limited to a key size of 56 bits; RSA keys could be any size. The
larger a key is the harder it is to crack, although with the size
increase the key runs slower with size. The RSA algorithms were
eventually patented and licensed to RSA Data Security, such
businesses as Apple, Microsoft, WordPerfect, Novell, and AT&T
implemented the RSA software into there system.
As the size and use of the Internet grows, the use of public key
encryption in our everyday lives will grow. The use of public key
is already found in transporting important information from
computer to computer on the Internet, such as credit card
numbers. When someone purchases something from a store on-line
there card is encrypted by the browser using the stores public
key, and then sent to the store in ciphertext, the store receives
the it and then decodes with there private key. With the age of
digital communication expanding everyday the use of public key
will become part of our lives just as using an envelope has
become yesterday's way of encrypting a letter.