[Cryptography] Spooky quantum radar at a distance

[John Denker]

I wrote:

>> This bag has been catless for many years.  I reckon stealth technology
>> is still effective against bush-league opponents, but I would be very
>> surprised if anybody could fly into Chinese airspace without being
>> picked up.

On 09/24/2016 03:49 PM, Watson Ladd wrote:

> Picked up is one thing. Shoot down?

Two words:  "Kill chain."

Initial detection is the first link in the chain.  Subsequent links
generally use technology that differs from the first.

>  If you don't have any
> interceptors, you will be relying on SAM missiles. 

That's fallacious.  Ex falso quodlibet.  The fact is, non-bush-league
operators have interceptors, with air-to-air missiles.  (Of course
they have surface-to-air missiles also.)

> Vietnam-era designs
> like the S-75 use shorter frequencies for technical reasons I don't
> recall, and so will not be effective against stealth planes.

That's irrelevant.  In the security business, it is bad policy to
assume the other team hasn't done anything or learned anything in
the last 40 years.  This applies equally to cryptology and missilery.

>  Bistatic installations cannot be easily mobile

That's false.  Assertions like this are easy to check.  I get 60,000
hits from:
   https://www.google.com/search?q=airborne+bistatic+OR+multistatic+radar

Even if such things were not already widely known, it would be prudent
to assume the opposition has such things in the closet, or under
development.  They would be stupid not to.

> Stealth is not about perfect undetectability, but about reducing the
> effectiveness of long-range radar based weapons

In missilery -- as in cryptology and a thousand other disciplines --
it is pointless to talk about "reducing" something without specifying
how much it is reduced, and at what cost.

If stealth "reduces" your chance of getting shot down from 100% to
99%, that's a "reduction" but it's not good enough, especially if
it comes at the cost of range, speed, rate of climb, maneuverability,
payload, and affordability.

> which for physics reasons have to use high frequencies.

Really?  What physics is that?  Please be specific.

Or don't bother, because even if it were true, it would be irrelevant.
Low frequencies aren't the only game in town.  Stealth aircraft still
show up on IR and on multistatic X-band.

>  The engagement range of a
> stealth aircraft is longer than that of its opponent, providing ample
> opportunities to destroy the opponent first.

That's untrue if the opponent also has stealth, and is combining long-
wave, multistatic, and IR to see you, while you can't see him because
you made a long string of false assumptions.

It's also untrue if the opponent is playing defense and you are intruding
on his turf, even if you have stealth and he doesn't.  He can have a
bazillion cheap unmanned transmitters in the rear echelon, which you can
see, plus a bazillion receivers and launchers along the front, which you
can't see.  By the time you get close enough to shoot at the transmitters,
the launchers can shoot you.

Even if you manage to get the shot off, you're using a 300,000 dollar
anti-radiation missile to take out a 10000 dollar unmanned transmitter.
Not a good exchange.  And then you discover that every transmitter
has several backups that you didn't know about, because they had never
previously been turned on.

> You cannot fit an L band
> antenna onto a SAM missile without serious size problems.

That's partly untrue and entirely irrelevant.  If you don't need
monostatic directionality, you can use a very small antenna.
 *) The 700 MHz cell-phone band has a long wavelength, longer even
  than L-band, yet can be sent and received by cell phones that are
  quite a bit smaller than a missile.  That's relevant, because if
  you do multistatic interferometry, resolution depends not on the
  size of each antenna but rather the size of the array.
    http://space-geodesy.nasa.gov/techniques/images/VLBI2.jpg
  This is related to the idea of "track-by-missile".

  That means you can launch 2N missiles to shoot down N supposedly
  stealthy intruders.  At $100,000 per missile and $100,000,000 per
  airplane, that's a good exchange.

 *) Instead, or in addition, you can fit a relatively prosaic L-band
  radar into an AWACS or even a fighter.
    http://www.ausairpower.net/APA-2009-06.html
  You can use that to vector the missiles to the right general vicinity.
  Then, for the last links in the kill chain, the missiles can use their
  own monostatic IR and/or multistatic short-wavelength radar, which do
  fit quite nicely.

====================

Here's a crypto-related tangent:  Reportedly, according to the Snowden
documents, the NSA believes a cyberattack from China purloined a great
many technical documents about the B-2, F-22, and F-35.
  http://www.spiegel.de/spiegel/print/d-126149146.html

One may conjecture that the Chinese were ROTFL when they saw the F-35.
  http://www.thedailybeast.com/articles/2016/03/17/military-admits-billion-dollar-war-toy-f-35-is-f-ked.html
  https://warisboring.com/fd-how-the-u-s-and-its-allies-got-stuck-with-the-worlds-worst-new-warplane-5c95d45f86a5