The 140 foot radio telescope at Green Bank, West Virginia.
SETI is the Search for ExtraTerrestrial Intelligence. The primary (and maybe only) search method currently being used is scanning the sky for radio waves that show some type of pattern that may indicate the source is coming from an intelligent source. This would then start the process that could possibly prove that we are not alone in this great big universe. For more information than I'm going to cover please visit the SETI Institute site. There is also a publication about this subject, SETIQuest that I have found on the web for this subject as well as Astrobiology(!).
I have been thinking much lately about encryption and compression and how it will affect society down the road. I have been doing this mainly as research for a novel I hope to one day finish. This has had me thinking in idle moments about such things. One of the thoughts I had was that pretty soon, most of the radio traffic on this planet will be either compressed and/or encrypted. Maybe in the next 25 years, maybe as long as 100 years from now. I then saw this trend as a problem as it relates to the SETI (the Search for ExtraTerrestrial Intelligence) Project.
Allow me to do a little background explanation here. Currently most of what we are broadcasting out into space is analog signal. Think of an analog signal this way, like a telephone. A magnet in a coil vibrates from the air vibrations (sound) and makes an electric signal. This signal travels through wires to a speaker, which is a magnet in a coil similar to what we started with, but now, the signal makes the magnet move in the coil, recreating the original sound. This is pretty simplified, but I think you see the point. The signal is analog, as the signal can take on any necessary properties that make the sound. The signal can be any rated value. One of the issues with analog signals is that they can become weak or damaged, and data loss can occur.
Now a digital signal is one that uses certain levels to mark either 0 or 1, off or on. The letter A in 8-bit ASCII (a standard computer depiction for letters) is 01100001, which comes out to the decimal number 65. The number 9 in 8-bit EBCDIC (another standard depiction) is 11111001, which comes out to the decimal number 249. More and more signals are turning into digital signals. The United States has just passed a standard for High Definition TV (HDTV) that uses digital signals. One of the positive attributes to digital signals is that, since they are nothing but numbers, certain numeric functions can be done to ensure that the data being carried in that signal are exactly what the origin specified them to be. This is known as error detection and error correction. This is a seperate issue from the compression and encryption I will be talking about. Computers can understand digital signals a whole lot better than analog signals.
Compression is the process of taking an amount of information, and then reducing the information through various ways and reducing the space that this information takes up, in a computer's RAM or hard drive, or beaming it via electricty through copper wires, via photons through fiber optics, or via radio waves through just about everything. If I record a 30 second sound, I can compress it down to much shorter than 30 seconds. Of course, to make it understandable I have to be able to decompress it. Compression is usually lumped into two kinds, lossless (you get an exact copy of what you compressed when you decompress it) and lossy (you get a copy of what you compressed, but it certainly won't be an exact copy). In everyday WWW surfing, you run into both kinds. Files in .GIF format are lossless, and files in .JPG format are lossy.
It's probably not important, but I'll describe the differences between the two ways of compression. A .GIF file is a standard graphics format that Compuserve started that has a limit of 256 colors per image. The kind of compression that they decided to use ensures that the the image you get out of the file is exactly the same as what you started with.
A .JPG or JPEG file format is another standard graphic file format that allows up to 16 million different colors in an image. The raw uncompressed image of a .JPG is 3 times the size that of a .GIF of the same resolution. Surprising as it may seem, a .JPG is usually much smaller than a .GIF file, as .JPG uses lossy compression that looses some of the details when it compresses an image. An uncompressed image will not be the same as the original image. This is alright, as long as not too much detail is lost, and the eye will not miss it. Follow the above links for more information.
Encryption is a more of a process of creating a copy of information that is secure, such that only the intended recipient(s) can read the information. This usually entails compression at some stage as well. There are various ways of doing encryption, from single key (You have a key that both locks the information and unlocks it) such as DES encryption, to double key (one key locks the information, the other key unlocks it) such as RSA public/private key systems. There are probably others that I don't know as well.
One more thing about both of these technologies. Good compression or good encryption result in output (what you have to decompress/decrypt) that looks like pure random junk, just like tuning a radio or TV to a non-existent station. What is usually called "white noise". You might be able to make out the beginning and end, then again maybe not.
Let's look at radio, which is what the SETI project is essentially about. They are trying to find a pattern that can be recognized as intelligent. Radio is a very controlled resource, especially here in the United States. The Federal Communications Commission (FCC) controls most of the radio spectrum, with very few "open" bandwidths left for use. In fact, some of these bandwidths are reserved for listening. Since this is a limited resource, compression for these finite resources makes a whole lot of sense. Encryption will also be used in some form to keep those people from receiving information they shouldn't be because they have to pay for it, or other reasons. Satellite broadcasts are encrypted for this reason.
Radio is just a little over 100 years old now, since Marconi made his first 2.4 kilometer transmission. Now let's suppose that it's another hundred years before all radio broadcasts are compressed/encrypted. We'll have a span of about 200 years of radio history for others to listen for. After that?
If whoever is listening doesn't know how to decompress the broadcasts and how to decrypt them or doesn't have the keys to the encryption, what are they going to see? White noise. No discernable pattern, Earth just becomes another "natural" object pushing radio waves into the universe. Maybe it will stick out in power, then again, it may not.
This means that extraterrestrials have a two hundred year window (at best!) to find us, if they are doing the same kind of search that we are. That is, if they can figure out just what the devil we are spewing out to the universe. Are they going to be able to discern the difference between an audio signal and a video signal? And what about current digital signals, which may or may not already be compressed/encrypted? Frequency modulation or amplitude modulation? And what about spread spectrum broadcasting that was patented by Hedy Lamarr? The problems are far from trivial.
Now let's flip flop it. If we assume that other extraterrestrial civilizations are developing at the same rate we are, we have a 200 year window in their history to find them. Maybe more, maybe less. Let's assume for argument that they are an order of magnitude slower than us. We get a two millenia window. Sure that sounds like a lot of time. But in the total time frame of the universe, that's less than an eye blink. We have to be looking in the right direction at the right frequency at the right time. Once we do have a fix, then we need some way of transforming what we receive into something. Hopefully we'll catch them soon enough to figure out how their early TV's work and be able to get actual images of what they look like. But a two thousand year window out of potentially hundreds of millions of years is nothing. And I think that is being truly optimistic.
Will there by any "plain traffic" sent out in the future? The problem may be such that some benevolent person or country sets up a transmitter to broadcast an unencrypted and uncompressed signal for others to pick up. If we can think of it, maybe the aliens out there have thought about the situation too, if I can allow myself a little anthropomorphism. The problems are there for both sides, but they can be overcome.
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Bryan Price / me@bryanlprice.com / Last modified 3/97 
