Data Encryption

Data Encryption Defined

Data encryption refers to the transformation of data into a form that makes it unreadable by anyone without a secret decryption key. It ensures that messages can be read only by the intended recipient.

Public-Key Encryption

Until quite recently, encryption methodologies suffered two major drawbacks. The first is that the process of encrypting and decrypting was very slow and laborious. Modern computers have solved this problem. In fact, it is now possible to encrypt text or speech faster than it can be typed or spoken.

The other major problem had to do with security. If Joe wanted to send me a private message, he would encrypt the message with a secret encryption key. In order for me to decrypt and read the message, I would need to get that secret key from Joe. We would have to trust a third-party (e.g. courier), send it by mail (either postal or electronic), or communicate it over the phone. If the key was somehow intercepted or stolen, then the encrypted message could be read.

Public-key encryption has solved this problem. Each user receives two keys: a public key, which is published in a directory to which everyone has access, and a private key, which is known only to the individual user. In this system, if Joe wanted to send me a private message he would look up my public key and use it to encrypt the message. Once I receive the message, I simply use my private key to decrypt it. In this way, public-key encryption provides a high degree of security.

Public-key encryption also provides a means of verifying the sender of a message. If Joe also wanted to prove that the message was in fact written by him, he would encrypt the message using his private key. Upon receiving the message, I would look up Joe's public-key in a directory, and use it to decrypt the message. If I end up with a readable message and not gibberish, then I know the message was encrypted with Joe's private key. So, public-key encryption also provides a method of including the digital equivalent of a signature, a way of proving the origin of a message.

Pretty Good Privacy

Pretty Good Privacy (PGP) was developed by Phil Zimmerman in 1976. PGP makes use of public-key encryption to prevent e-mail messages and documents from being read by anyone but the intended recipient. It has proven itself quite capable of resisting even the most sophisticated forms of analysis aimed at reading encrypted messages.

Why should you encrypt your e-mail? E-mail should be encrypted for the same reason that you don't write all of your personal correspondence on the back of a post card. E-mail is far less secure or private than postal mail. Using an encryption package like PGP should not in any way imply illegal activity. It is just a way to keep personal thoughts personal. A proponent of PGP, known as Xenon, puts it this way:

Pretty Good Privacy is available as freeware all over the Internet. Check out the International PGP Home Page to find out how to get a copy.

Anonymous Remailers

An anonymous remailer allows people to send e-mail messages or to post messages to a Usenet group without the recipient knowing the sender's name or e-mail address. The anonymous remailer receives messages with the destination address attached, strips off the sender's name and location, and then resends the message to the given destination address.

Anonymous remailers can use public-key encryption to prevent an outside observer or spy from reading the destination addresses on intercepted messages coming in to a remailer. Suppose Jane wants to send e-mail to Bob without disclosing her identity. She would encrypt her message using Bob's public-key. Then she would use the anonymous remailer's public key to encrypt the destination address (Bob's address) together with the encrypted message to Bob. The remailer uses his private key to decrypt the message leaving him with a destination address he can read but a message that he cannot.

One potential problem with this method of maintaining privacy is that it is dependent on the reliability of the remailer. What if he is working for the spy or observer? The solution to this problem is to route the message through a number of anonymous remailers. So long as one of them is honest, there will be no way to match up the sender and receiver.

Anonymous remailing is a free service on the Internet. Of course it has to be free - how could the remailer administrator charge people who want to maintain maximum privacy? There are currently over 20 remailers available. A popular remailer is provided by Community ConneXion. You can practice by sending a message to yourself.

Key Escrow Encryption

One can easily imagine the use of encryption products for covering up serious criminal activity such as buying and selling trade secrets, tax evasion, or even the hiring of contract killers. All of these activities become much easier in a world where criminals can operate without revealing their physical location or proprietors.

Key-escrow encryption is a new type of encryption that attempts to ensure that legitimate privacy interests are maintained while still allowing authorized government officials to gain access to communications. An escrow is defined as:

Key-escrow encryption couples strong encryption with emergency decryption capabilities. In the event of an emergency, an organization can obtain their recovery key from their escrowed agent. Investigative or intelligence agencies can only gain access to the organization's recovery key if they follow strict procedures to obtain a court order. In this way, the communications and files of the organization remain completely private unless an authorized official, with a court order, deems it necessary to gain access (i.e the organization is suspected of being involved in illegal activity).

The Clipper Chip

The highly controversial Clipper Chip was introduced by the Clinton administration and uses key-escrow technology. It is purported to prevent terrorists, drug dealers and foreign spies from using modern technology to make themselves impervious to wire-taps but still provide ordinary citizens with the benefits of electronic privacy.

Each Clipper Chip has two keys built into it and both keys are required to decrypt any message encrypted by that chip. Two escrow agencies are established. One holds the first key (in a database) of every chip ever produced. The second escrow agency holds the second key of every chip ever produced. A law enforcer with a court order for a wiretap can take the court order and the serial number of the chip to be tapped to the escrow agencies and obtain the two keys.

Dorothy Denning of Georgetown University has written an interesting and thought-provoking article entitled Future of Cryptography. The article discusses key-escrow encryption, the Clipper Chip, and the realities of crypto anarchy.

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This page was written by Sandra McCallum.

Last modified March 28, 1996