A Look at Public Key EncryptionEncryption 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 canbe read by anyone. Example of encryption can be found in history,for example in the era of the Cold War, the Solviet Union and theUnited States would send electronic messages to one militarypoint to another, encrypted. If the enemy intercepted themessage, they would have to crack this message to get theinformation. Typically when governments used encryption they useda very complex method of encrypting messages. Encryption does nothave to be complex; the Captain Video Decoder Rings that we hadas children used encryption. You’d encode your secret message,such as “Meet me by the swings,” by replacing the letters of thealphabet with substitute letters from a certain number of placesaway.

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For example, let’s say we decide to use the key “+4.” Thatwould mean we’d switch each letter in our message with the letterthat comes four places later in the alphabet. D would become H; Rwould become V, and so on.

You, or anyone else who knows the keycan easily switch the H back to a D, the V back to an R, andfigure out where to meet. Theses two examples are on oppositesides of the spectrum, but both have their similarities and theirdifferences.The major difference complexity, the government paysmathematicians to research complex algorithms by which to encodethe messages, like the system used by Captain Video but thesealgorithms are complex enough that if you tried to crack them itwould take you decades with even the most powerful computertoday.

This complex mathematical code is what makes the textsecure to anyone who tries to crack it. Some similarities we canfind in these two examples are their use of the key, theunlocking instructions, to decode the message. They only used onekey to encrypt and decrypt the messages. This creates problems,security problems.

The single key must itself be kept verysecret, while somehow still being transmitted to the personreceiving encoded messages. Even if the key is transmittedsafely, which you can never know for certain, the recipient cannever be sure received messages haven’t been intercepted by theenemy, altered, and passed along to create havoc and disarray.This was a major fault of the one key system that made it veryvulnerable. The answer to this problem can in 1976.

Up until 1976 no one outside the government or at least outsidethe government’s control, performed any serious work incryptography. The National Security Agency (NSA) was in charge ofall advancement of cryptography, and that changed when a 31-year-old computer wizard named Whitfield Diffie came up with a newsystem, called “public-key” cryptography.Diffie tended a complicated multi-user computer system atMIT. He became troubled with the problem of how to make thesystem, which held a person’s work and sometimes his or herintimate secrets, truly secure.

The traditional, top-downapproach to the problem- protecting the files by user passwords,which in turn were stored in the electronic equivalent of vaultstended by trusted system administrators- was not satisfying. Theweakness of the system was clear: The user’s privacy depended onthe degree to which the administrators were willing to protectit. Diffie recognized that the solution rested in a decentralizedsystem in which each person held the literal key to his or herown privacy. He tried to get people interested in taking on themathematical challenge of discovering such a system, but therewere no takers. It was not until the early 1970s, when the peoplerunning the ARPAnet were exploring security options for theirmembers, that Diffie decided to take it on himself.

By then hewas at Stanford, under the thrall of David Kahn’s work. Theproblem with the existing system of cryptography was that secureinformation traveled over insecure channels. In other words, amessage could be intercepted before reaching its recipient. Thepassing of the key Kahn realized also was a major problem. Theproblem got even worse when one tried to imagine encryptionemployed on a massive scale. The only way to do it, really, wasto have registries, or digital repositories, where keys would bestored.

As far as Kiffie was concerned, that system was screwed,you wound up having to trust the people in charge of theregistry. It negated the very essence of cryptography, tomaintain total privacy over your own communications.In May 1976, collaborating with Stanford computer scientistMartin Hellman, Diffie cracked both problems. His scheme wascalled public-key cryptography. It was a brilliant breakthrough.Every user in the system has two keys – a public key and aprivate key. The public key can be widely distributed withoutcompromising security; the private key, however, is held moreclosely than an ATM password- you don’t let anyone get at it.

Forrelatively secret mathematical reasons, a message encoded witheither key can be decoded with the other. For instance, if I wantto send you a secure letter, I encrypt it with your public key(which I received from you), and send you the ciphertext. Youdecipher it using your private key. Likewise, if you send amessage to me, you can encrypt it with my public key, and I’llswitch it back to plaintext with my private key.

This principle can also be used for authentication. Only oneperson can encrypt text with my private key-me. If you can decodea message with my public key, you know beyond a doubt that it’sstraight from my machine to yours.

The message bears my digitalsignature.By 1977, three members of this new community created a setof algorithms that implemented the Diffie-Hellman scheme. CalledRSA for its founders – MIT scientists Rivest, Shamir, and Adleman-it offered encryption that was likely to be stronger than theData Encryption Standard (DES), a government- approvedalternative that does not use public keys. The DES system islimited to a key size of 56 bits; RSA keys could be any size. Thelarger a key is the harder it is to crack, although with the sizeincrease the key runs slower with size.

The RSA algorithms wereeventually patented and licensed to RSA Data Security, suchbusinesses as Apple, Microsoft, WordPerfect, Novell, and AT;Timplemented the RSA software into there system.As the size and use of the Internet grows, the use of public keyencryption in our everyday lives will grow. The use of public keyis already found in transporting important information fromcomputer to computer on the Internet, such as credit cardnumbers. When someone purchases something from a store on-linethere card is encrypted by the browser using the stores publickey, and then sent to the store in ciphertext, the store receivesthe it and then decodes with there private key.

With the age ofdigital communication expanding everyday the use of public keywill become part of our lives just as using an envelope hasbecome yesterday’s way of encrypting a letter.

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