HIGH TECH TUESDAY
Unbreakable Code
Edited by B. Virtual
According to the ACLU, "ECHELON is perhaps the most powerful intelligence gathering organization in the world." Several credible reports suggest that this global electronic communications surveillance system presents an extreme threat to the privacy of people all over the world. According to these reports, ECHELON attempts to capture staggering volumes of satellite, microwave, cellular and fiber-optic traffic, including communications to and from North America. This vast quantity of voice and data communications are then processed through sophisticated filtering technologies.
This massive surveillance system apparently operates with little oversight. Moreover, the agencies that purportedly run ECHELON have provided few details as to the legal guidelines for the project. Because of this, there is no way of knowing if ECHELON is being used illegally to spy on private citizens.
Most people know little about computer security. They don't realize that their e-mail messages are not sent point-to-point. Instead, they are sent from one computer to another. In fact, e-mail is like sending a postcard--anyone who comes across it can read it.
So without the knowledge of either the sender or the recipient, e-mail can easily be intercepted and copied. To remedy this problem, there are quite a few systems for encrypting e-mail on the market today. PGP is the world's de facto standard for e-mail encryption and authentication, with more than 6 million users.
Don Fitzwater wrote in Computer User:
In conventional cryptosystems, such as the U.S. Federal Data Encryption Standard (DES), a single key is used for both encryption and decryption. This means that a key must be initially transmitted via secure channels so that both parties can know it before encrypted messages can be sent over insecure channels. This may be inconvenient. It also begs the question that if you already have a secure enough channel for exchanging keys, then why do you need cryptography in the first place?
Public-key cryptography solves this problem by using two keys instead. In public-key cryptosystems, everyone has two related complementary keys, a publicly revealed key and a secret key (frequently called a private key). Each key unlocks the code that the other key makes. Knowing the public key does not help you deduce the corresponding secret key. The public key can be published and widely disseminated across a communications network. This protocol provides privacy without the need for the same secure channels that a conventional cryptosystem requires.
Anyone can use a recipient's public key to encrypt a message to that person, and that recipient uses her own corresponding secret key to decrypt that message. No one but the recipient can decrypt it, because no one else has access to that secret key. Not even the person who encrypted the message can decrypt it.
Message authentication is also provided. The sender's own secret key can be used to encrypt a message, thereby signing it. This creates a digital signature of a message, which the recipient (or anyone else) can check by using the sender's public key to decrypt it. This proves that the sender was the true originator of the message, and that the message has not been subsequently altered by anyone else, because the sender alone possesses the secret key that made the signature. Forgery of a signed message is not feasible, and the sender cannot later disavow his signature.
Could the battle between code-makers and code-breakers be ending? Physicists are putting the finishing touches to a new way of encrypting messages that is more secure than any past cipher, writes contributing editor Justin Mullins in "Making Unbreakable Code" in the May 2002 issue of IEEE Spectrum.
The technique, known as quantum cryptography, combines a decades-old method of encryption, mathematically proven unbreakable, with a novel theft-proof method of distributing the encryption key, whose security is grounded in the laws of quantum mechanics.
The novelty is the technique's use of a quantum property of photons, their polarization. Should an eavesdropper listen in on the transmission of a key, the strange laws of quantum mechanics mean that the photons are inevitably--and detectably--disturbed. When eavesdropping is detected, a new key can be sent. Only when the sender and receiver are sure their key is secure do they use it to encrypt and transmit information over conventional channels such as e-mail.
Experimental encrypted messages are already being sent and received securely over tens of kilometers of optical fibers and through the air. The first portable quantum cryptography machine, unveiled last summer at the Los Alamos National Laboratories, can send encrypted messages through the air over dozens of kilometers and works day or night in good weather and in bad according to develooper Richard Hughes. And in Geneva, Switzerland, a small start-up called ID Quantique has begun marketing a commercial quantum cryptography device that works with an optical-fiber connection.
Researchers predict that it will not be long before ultra-secret messages are routinely transmitted this way. But because the technology used to implement quantum cryptography isn't perfect, some limitations remain, according to Mullins. So physicists and engineers still have some work to do before the technique becomes widespread.
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