ADSB Anonymous Mode?

[moosepileit]

Two!

FWIW, browsing around, supposedly ATC will be eventually able to tag up your ADS- B anonymous 1200 VFR code symbol and see your ID.

Also, the "system" will store ALL tags and tracks in a searchable/reviewable format.

True/False?

[GWZ]

I don’t think they can ever tell who you are if you are in anonymous mode. They go through quite a bit to generate an “almost” random ICAO. It involves taking the 12 least significant bits from both the lat and long of your current position adding that together, multiplying that by 4096 then exclusive “ORing” it with your ICAO (if available). If your assigned ICAO isn’t available it uses current time. So really you don’t even need an assigned ICAO to fly around in anonymous mode.

[Steve Iacoviello]

Originally Posted by rv7charlie

Are you sure about that? I think that all it suppresses is your N number; isn't the raw code of the ADSB unit (which is tied to your N number in the FAA database) still transmitted?

As I understand it anonymous mode transmits a random code. If the random code was tied to your “N” number and could be decifered we would know about it. One would have to assume that manufacturers such as Garmin would be complicit. Not ready to believe that.

[snopercod]

Originally Posted by GWZ

It involves taking the 12 least significant bits from both the lat and long of your current position adding that together, multiplying that by 4096 then exclusive ?ORing? it with your ICAO (if available).

Very crypto-like.

[RVbySDI]

Originally Posted by Toobuilder

Maybe for the millennials, but this Gen Xer is going to cling to it until my deathbed.

+1 for this Baby Boomer as well.

[Larry DeCamp]

As much as I respect the VAF braintrust, this thread leaves me cluleless. I have no intention of doing wrong, and share disdain for big brother. But, can somone identify themselves as having bottom line credentials on the topic and tell us the bottom line ?

[Timberwolf]

I can say when a parameter wasn?t meeting spec on my navworx unit in anonymous mode, the FAA still called and knew exactly where to track me down to tell me it was out of spec. That confirmed it for me that it may be anonymous to other aircraft, but not to the FAA.

[Alan Carroll]

Originally Posted by moosepileit

Two!

FWIW, browsing around, supposedly ATC will be eventually able to tag up your ADS- B anonymous 1200 VFR code symbol and see your ID.

From FreeFlight Systems' web site:

"How does 978 UAT do it differently? The 978 UAT rules allow for an ?anonymous? operating mode for aircraft flying VFR, and most avionics manufactures? equipment support this (but it?s advised to check first ? it is the manufacturer option to decides if they want to include this feature). If the option is available, it can be enabled during the installation. When the aircraft is on the ground and during the first few minutes of flight (so ATC can establish a track), the 978 UAT sends out the ICAO code and Flight ID. After that, as long as the squawk is set to ?1200,? the 978 UAT automatically scrambles those two fields using a random encoding scheme. ATC is able to maintain track, so you are safely ?in the system? but other aircraft and observers on the ground with receivers (like ?Flight Radar24?) loses all of the identifying info ? with no way to correlate it back to a specific aircraft or aircraft owner."

If this is correct then the anonymous mode really only prevents third parties from seeing your flight ID.

[Larry DeCamp]

So I conclude I can eliminate a "switch" on the panel for anonymous if the purpose is to keep big brother at arms length. That said, why would I care about third parties if the FAA has the data, if a serious accusation should arise ?

[moosepileit]

I followed Gunter's post and read the 68 page RTCA ADSB UAT document. Alan's reply was the info I alluded to earlier.

Free, link below, if you are over-caffinated

https://www.google.com/url?sa=t&sour...=1550418096139

It has the schemes for all the data segments.

While the ICAO number is able to be anonomized "self assigned temporary number"- your CALL SIGN or for most here, our N#/registration number field is always active.

So, NOT really anonymous from ATC/FAA and possibly the "how/why" is my conclusion.

I might play with "978dumps" from adsbexchange to do a D.H. level test.

Flightaware and other sites can decode/upload 978mhz UAT, but most only use 1090mhz feeds. As long as they use the ICAO number field, there is the anonymity, to that extent.