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The Internet and Public Key Encryption

February 1, 2005

A public radio commentary

As an eight year old I spent many enjoyable hours with a book on codes and ciphers, but in today's world cryptography is no longer child's play. Our networked, computer world depends on it. Everything from a credit card purchase on the web to international banking. This networked financial world runs only because of a revolutionary breakthrough in cryptography.

In the mid-1970s a handful of young computer wizards invented a new way to encode information. They were distrustful of the government since they'd lived through Vietnam and the Watergate scandal. So, they thought deeply about ways to preserve privacy in the emerging computer age. They solved an age-old problem with codes: How to tell the recipient of the coded message how to read it.

Julius Caesar, for example, sent messages to his generals encrypted by shifting the letters of the alphabet a fixed amount. In order for his generals to read the messages Caesar also had to send along the key by a separate courier, which could be intercepted by enemies. Think of how cumbersome this would be in our internet age.

Consider using your credit card to purchase something from a web site. If you encrypted your card number the way Caesar did, you'd need to also ship the key to the web merchant. It wouldn't be safe to send in the open via email, so you'd have to do something like to drive it there, or mail it, which might not be secure.

To overcome this these young mathematicians invented public-key encryption, which breaks apart the coding and decoding. Here's how it works: I list my public key anywhere - maybe on my web site. With this you can encrypt a message to me, but here's the special part: You cannot then decrypt the message. In fact, you don't need to give me any special instructions about how to read the message. I have instead what's called a "private key." I'm the only one that needs to have this. This truly revolutionary separation of encoding and decoding makes possible our web-based internet world. For example, your web browser uses a merchant's public key to encrypt credit card information, then the merchant uses their private key to read it. No mailing of secret stuff needed at all.

Now, of course, like all technological developments this has a down side. If you can send your credit card information so that prying eyes can't view it, then a terrorism group can plan with the same degree of privacy. This has put cryptography under attack from the U.S. government for years - including banning certain software and even prosecuting its developers. Cryptography seems so exotic, and so much the domain of spies and secret agents that we lose sight of how essential it is to our modern everyday world. So, like all measures against terrorism, it abridges our freedom whenever we restrict the use of encryption.

Copyright 2005 William S. Hammack Enterprises