[nabla9]

Don't even have to be encrypted. Just compressing the data makes it hard to separate from noise.

Turbo Codes and LDPCs used to transmit data over noisy channels (like NASA uses in deep space satellite communications or UMTS and LTE networks) look just like noise. I don't think Seti or astronomers have ever tried to analyze noise for some alien codec that might be transmitting.

[jerf]

"I don't think Seti or astronomers have ever tried to analyze noise for some alien codec that might be transmitting."

They can't. "It looks like noise" isn't a metaphor, it's a mathematical truth... it is indistinguishable from noise.

This is, IMHO, another one of those cases where people like to do a bit of social signaling with their fashionable misanthropism, but we actually know quite a bit about this problem. The optimal solution for using the electromagnetic spectrum for signaling, even with our current level of technology, is to use it in such a way that it looks like noise due to compression and due to not using any more power than necessary, in any direction other than the necessary one. Of course aliens do not sit there using four or five (if not six) orders of magnitude more power than necessary by broadcasting in all directions instead of using a directional beam, and of course they do not sit there and transmit in an uncompressed format that is an obvious signal, so of course we don't see their transmissions. It would be bizarre if it were otherwise. We have no reason to believe that aliens, who live in the same universe as us and are subject to the same engineering constraints as us, would be particularly prone to missing this incredibly obvious optimization.

(Math may be the one true cross-universe universal, but within this universe engineering is pretty universal too.)

[Dylan16807]

> They can't. "It looks like noise" isn't a metaphor, it's a mathematical truth... it is indistinguishable from noise.

That's a bold statement.

Encryption makes the bits look like noise, but you still have to turn bits into signals, and that has structure.

Efficient signaling methods look a lot like noise, but any safety margin makes it distinguishable from noise.

Beyond that, increases in noise in specific bands are still a notable event.

Even if it's spread across many or all bands, what is causing that.

Only highly directional signals would be hidden from us.

And of course transmissions might be too weak to see, but that is not what we're talking about here with the type of signal.

[TheOtherHobbes]

Problem - humans have been doing all of the above for decades, occasionally as a deliberate attempt to communicate, but mostly by accident.

So I can't see how your comment has any basis in fact.

You're only going to compress a data channel if you're in a hurry. When a message is going to take decades or centuries to get somewhere, you're more likely to keep the encoding as simple as possible to increase the chances of reception.

Besides that, I can't imagine radio being used for interstellar communication at all. It's fine for "Is anyone there?" but unless your aliens live at geological rather than biological rates, it's far too slow for almost anything else.

[jerf]

Compressing increases bandwidth, which is forever going to be at a premium. If you want to improve reception reliability, you put error correction on top of that. This is all off-the-shelf tech here on Earth, to say nothing of what aliens can come up with.

"Besides that, I can't imagine radio being used for interstellar communication at all. It's fine for "Is anyone there?" but unless your aliens live at geological rather than biological rates, it's far too slow for almost anything else."

Well, it's the fastest thing available unless you're basically willing to hypothesize magic. Anyone willing to do so is welcome to do so, and I'm serious about that; I just advocate that you be aware that you've switched to advocating magic. There's a difference between reasonable speculations based on real physics and arbitrarily advanced engineering, vs. new physics that despite all our research we still have little more than a whiff of, if that, and keeps crawling into ever more exotic energy domains to even peek at.

[rz2k]

I think we are talking about overhearing communication between aliens speaking the same "language", where compression makes even more sense over a difficult channel. Consider data transmitted from spacecraft in our own solar system. The signal is quiet, and the bitrate is very slow. They could send uncompressed data if it is were easier to receive, but instead they recognize the bitrate as a physical constraint and optimize for information per bit. Uncompressed data could provide an advantage in terms of redundancies making errors more apparent and often recoverable, but error correction algorithms are both more robust and more efficient.

The point is that compressed transmission actually is simpler, and a formalized error correction scheme is much more reliable than relying on redundancies that arise by chance.

What about the parent comment belies anything factual? There is no data on alien transmissions, and the efficiency of compression and formalized redundancies just is, as a result of the math, not as a finding of collected data, even if real world data confirms what is mathematically understood.