I am interested in authentication - how identity is verified - in civilian aviation radio transmissions. I know that when someone is speaking on the radio he tells his call sign. But is there any other system that verifies the identity of the person speaking besides just the call sign that he claims to have?
I am interested not only in how ground ATC verifies which aircraft is speaking, but also in how aircraft ensure that they are speaking to a real ATC facility.
This is a reasonable question, and to an outside the simple answer of We don't / can't might seem a little bit jarring.
After-all, we live in a time of hacking, terrorism and so on and I can certainly see how this looks like a simple vector to create some havoc.
So, what's to stop somebody from setting themselves up with a Radio Transmitter and deciding to be Air Traffic Control for the day? Absolutely nothing. In fact, lower power handheld air-band transceivers can be purchased legally and cheaply by anyone. I have one near me - I could literally turn it on now and declare myself [Local Airport Tower]
However - the thing about Airband radio is that it's wonderful in its simplicity. At its core is AM radio which is basically unchanged since the early 1900's. This means a few things:
Pilots aren't automatons. We listen and build up a picture, we learn normal procedures and can hear stress in somebodies voice. We also know who we were speaking to. Combined with a decent situational awareness, we don't just do things without thinking - you can't just pipe up on the radio and ask an aircraft to fly into the ground.
And even if you did, and they initially believe you, real ATC is going to hear your readback and ask what the hell is going on.
By way of analogy, imagine you've snuck in on a conference call between an employee and a boss. And you start trying to speak on behalf of the boss - it's going to last all of 1 second before somebody realises something is going on. I think people tend to think of ATC as somewhat robotic, but it's still a human interaction and any good pilot will understand why they're being given instructions.
To attempt to interfere in Air Traffic Control in a way that is believable by the pilots is going to be incredibly difficult. You won't be able to use normal phraseology and cadence if you're attempting to step on real ATC, and that will concern the pilot. To do that for more than a few seconds and to to cause some kind of conflict with multiple aircraft is verging on the impossible.
The most likely outcome is more a denial of service, rather than some kind of spoof. It's not really a great vector to cause any damage. A nuisance, certainly and absolutely dangerous (and there's a reason it's very illegal!) but there are well established procedures for disruption in communications.
I've focused primarily on somebody trying to be ATC here, which is the way in which somebody on the ground would likely go about trying to make a mess. As for pretending to be a plane - firstly there are more technical difficulties because you'll be transmitting Ground -> Ground. I live within 2 miles of my local airport and often struggle to receive their transmissions when I'm at home.
Pretending to be a real plane that currently exists in the sky poses the same problems as above and any facility with RADAR is going to know something isn't right. Again, it might cause some initial confusion but you're unlikely to persuade somebody of something.
You could, in theory, pretend to be a light aircraft with no (or a faulty) transponder but really to what end? I guess you could cause a little disruption before somebody realises you're having a laugh but we're more into the realm of 'pranks' (Not that it's funny) now rather than serious risk.
So let's gloss over the technical details for getting a tower setup that is strong enough to reach far enough to really "drownd out" the proper ATC frequency. And keep in mind that while we are glossing over this, it's not the strongest transmitter wins, two or more transmitters would mesh and just make static and noise. But let's ignore that for now and say that got your setup working, and you're somehow, drowning out real ATC with your own signal.
First ATC is not in control of the plane, so if ATC asked a pilot to do something odd, the pilot can just refuse. There are very, very few instances where ATC has real authority. Mostly that authority is more like, yes you can enter this airspace, or no you can't. Media makes ATC (in movies) seem that it's in control and it tells pilots what to do. In fact, they are more of a service that makes sure planes don't smack into one another. That said if you ignore ATC you had better have a good reason because you're effectively ignoring the "thing" that is telling your X is safe and Y isn't.
Next, there are many "kinds" of ATC, and some of them have more communication with the pilot then others. For example, TOWER and APPROACH "levels" of ATC will talk a lot to pilots as it's their job to make sure planes are landing and taking off safely (glossing over a lot here). GROUND ATC is usually responsible for moving the plain around on the ground at an airport. CENTER level of control doesn't really talk to planes much, they're responsible for, essentially, all the space not around an airport, and generally, don't have much to do with the actual airplane. They don't sit around and go "Yeop your still ok, keep going that way." Though they can talk to planes it's usually to help them avoid other planes and to avoid weather.
Finally, there is the fact that there is a "normal" set of things each level of ATC may ask you to do. For example, GROUND will never tell you to change altitudes, TOWER only controls a very small space around the airport, etc. APPROACH and DEPARTURE may be the most "vulnerable" as they are the ones who handle making sure planes are not running into each other during takeoff and landing. BUT, every airport where it would be a problem has published SIDs and STARS along with approach procedures. So really all ATC does is say "Ok, you're not going to hit someone if you go do the published procedure". There are also published rules on how close planes can get to another. So again, even if you nailed the phraseology, you could not convince a small Cessna to get to close to a Airbus 320. As you stared to do things to move them close together, they would notice they're doing something wrong and refuse.
So while I suppose you could convince a pilot that you were ATC, all you could really do is actually do ATC's job. Not doing ATC's job correctly would just make the pilots go, "Umm, no"
Not that I am aware of. Usual protocol when a call is initiated by a pilot:
who you are calling (Clearance Delivery, Ground, Tower, Approach, Center)
who you are/type of plane
where you are
what you want to do.
Example: Hanscom Ground, (who you are calling)
Nxxxxx, Cessna Cardinal (who you are and what type plane)
on east ramp with Information Echo, (where you are and that you have the local wind and in-use runway information)
ready to taxi for departure. (what you want to do)
Who you are calling will read back who you are (they may be monitoring more than 1 frequency and not always catch it all), and then proceed from there.
If you don't announce yourself to start the "conversation" you will not be granted clearance into controlled airspace.
Civilian pilots are identified and tracked in the same manner an any other pilot in controlled airspace - radio communications. Certain airspace (class E and G) do not require radio communications with ATC. If no flight plan is on file or activated, they will be unknown targets. Another means to identify aircraft are, enter establishing ATC communications, they are assigned a specific transponder code which then is associate with their radar returns, making it easy for controllers to know who’s who.
