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A Look At Public Key Encryption

A 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.

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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 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.


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