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Link 16 datalink

overscan (PaulMM)

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I really don't know much about Link 16 datalink. Here's a picture of a Link 16 display- has anyone researched this area?
 

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yahya

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From my old notes: Link-16 a.k.a. TADIL-J is a TDMA-based secure, jam-resistant, high-speed digital data link which operates in the 960–1215 MHz band. Information is typically passed at one of three data rates at least in the older implementations: 31.6, 57.6, or 115.2 kilobits per second, although the radios and waveform FHSS itself can support throughput values well over 1 Mbit/s. Mode of operation: Fixed Frequency or Frequency Hopping. Believed to have a 3 MHz bandwidth.
 

LukaszK

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Hi.
Look on game tutorial
I know this is only game but symbology and general approach may have sth from reality
 

ferpe

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This presentation covers the design of secure physical layer communication designs and includes Link 16/JTIDS. It's an L-band frequency hopping (960Mhz to 1215Mhz) Direct Sequence Spread Spectrum physical layer with a digital encryption layer.
 

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I remember a moderate amount of detail about it. Do you have any particular questions?

This is a decent introduction, albeit a little bit dated at this point. Since I have been out of that world for more than 20 years, I'm not sure how much has changed (a few quick googles suggest that sending J-series messages over IP bearers is very much a thing at this point - I suspect that is primarily between fixed nodes, but the Link-16 physical layer is just insanely profligate in terms of spectrum utilized per delivered message bit.
 

stealthflanker

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I'm curious if one can arbitrarily change the encryption key/generate encryption key on their own for this datalink system without requiring permission from US.

It could be a very rare case but we know Greece and Turkey are at odds, which might turn explosive. Should it went south, we know both nations have US made fighters and naturally both may have Link-16 in their posession. This opens up opportunity to "listen" to each other's emission and potentially gain access to each other's network.
 

marauder2048

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I'm curious if one can arbitrarily change the encryption key/generate encryption key on their own for this datalink system without requiring permission from US.

You mean allied key management? It's totally up to them. If they wish to share their keys with everyone else there are
formal/encrypted key sharing mechanisms for doing so.

They are free to share network keys for lower privilege networks while reserving higher privilege keys for their
own internal networks. It's how Link-16 was (kinda) designed; segregation by key.
 

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One thing that I don't know (and if I did know of course I could not say; thus I am free to speculate) is how cryptographically secure the hopping sequence is (note that link-16 uses different encryption for hopping (TSEC) and message content (MSEC)). The people who designed Link-16 were plenty smart, but I'm not sure how well they were able to predict the 2020 state of the art in fast cracking (a particular thing which is my speculation regarding the type of generator used for Link-16's pseudorandom hopping sequence).

Obviously anybody with Link-16 hardware and autonomous keymat generation capability can mount a chosen plaintext attack on the hopping sequence. If the sequence is crackable in near realtime, then it is also exploitable for both ELINT and jamming purposes. The frequency dwell time is about 13 usec (more precisely, the hop rate is 77 kHz - I'm too lazy to go back and look up the guard times :) ) so it is straightforward to create a frequency synthesizer that can match and jam or track it.
 

marauder2048

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One thing that I don't know (and if I did know of course I could not say; thus I am free to speculate) is how cryptographically secure the hopping sequence is (note that link-16 uses different encryption for hopping (TSEC) and message content (MSEC)). The people who designed Link-16 were plenty smart, but I'm not sure how well they were able to predict the 2020 state of the art in fast cracking (a particular thing which is my speculation regarding the type of generator used for Link-16's pseudorandom hopping sequence).

Obviously anybody with Link-16 hardware and autonomous keymat generation capability can mount a chosen plaintext attack on the hopping sequence. If the sequence is crackable in near realtime, then it is also exploitable for both ELINT and jamming purposes. The frequency dwell time is about 13 usec (more precisely, the hop rate is 77 kHz - I'm too lazy to go back and look up the guard times :) ) so it is straightforward to create a frequency synthesizer that can match and jam or track it.

For a datalink that's not particularly jam resistant, non LPI, not LPD, the vulnerability of a pseudo-random hopping sequence is about
the least of the major concerns.

Aside from as a weapons datalink, Link-16 is pretty much moribund in the high-end threat environment. For weapons, it doesn't really
matter if you crack the encryption in near-realtime since you've been hit and destroyed in hard realtime.
 
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stealthflanker

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You mean allied key management? It's totally up to them. If they wish to share their keys with everyone else there are
formal/encrypted key sharing mechanisms for doing so.

They are free to share network keys for lower privilege networks while reserving higher privilege keys for their
own internal networks. It's how Link-16 was (kinda) designed; segregation by key.

Are those keys assigned by US or the nation in possession of Link 16 can generate their own key ?
 

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