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Nearby peer discovery without GPS using environmental fingerprints

svendewaerhert.com

21–27 of 27 posts

Re: Nearby peer discovery without GPS using environmental fingerprints

#21

Earlier quoted context omitted.

Thanks for the detailed response! I completely missed the band division / similarity plan - I’ll read more thoroughly next time. I thought about geo largely because it radically changes the order of magnitude of work necessary; it lets you segment ‘possible’ subsets of APs down to sets of say 100, not millions, and changes the combinatorics. A side effect is knowing a rough spatial location. Off the top of my head, I…

I see, this sheds some new light on your initial concerns. I'm aware an attacker can keep pretending to be inside an environment once they've seen it. I wasn't accounting for a scenario where an attacker has a huge database for queries like coords -> list of wifi networks. I was under the assumption services like Wigle only provided the reverse lookup (wifi -> coords). Indeed an attacker could potentially reverse the…

> I see, this sheds some new light on your initial concerns. I'm aware an attacker can keep pretending to be inside an environment once they've seen it. I wasn't accounting for a scenario where an attacker has a huge database for queries like coords -> list of wifi networks

I think this is the issue, is these datasets are out there and at least big tech companies have them since they're used to assist with GPS. I was about to post the same thing as above but saw vessenes beat me to it.

Without thinking about it too hard, the two directions I see are either making observations of the environment in real-time that is only relevant at that time (IE sniffing actual wireless frames, even if they're encrypted and making observations on them, however, most devices won't let you go into promiscuous mode and do this) or encrypting the messages in flight so only participants can decrypt them (IE a model like the signal protocol with E2E message encryption).

Anyways, this is a cool approach, but that risk occurred to me as well about the ability to just brute force the entire dataset to decode every location.

Re: Nearby peer discovery without GPS using environmental fingerprints

#22
This could be useful for dynamic clique routing used in mesh networking in large crowds. Although I would think one would need to do the peer discover prior to any Internet shutdown events. It gets around the problem of GPS spoofing, and physical barriers that traditional GPS based groupings have.

Re: Nearby peer discovery without GPS using environmental fingerprints

#23
post #7

There are a couple of difficult cryptographic-type problems with this plan. (Which I like, by the way). I don’t think it’s privacy preserving, and I also don’t think it works well for finding shared locations as currently specified. Also, the privacy and the finding are in direct opposition to each-other, which isn’t always a comfortable system dynamic. On the one hand, a simple hash of ESSIDs near you, if you take a…

> Also, the privacy and the finding are in direct opposition to each-other, which isn’t always a comfortable system dynamic. ... or some sort of group key sharing

Perhaps you might consider a pinsketch in the manner proposed for cryptographic biometric security. https://arxiv.org/abs/cs/0602007

I contributed to a fast implementation of the underlying algorithim: https://github.com/bitcoin-core/minisketch

With it two peers could compare their BSSID environments and learn ~nothing about each other unless they were nearly matching.

I can see how one could use it for location based key agreement for mutual authentication-- not as obvious to me how to apply it to privacy preserving location.

The latter would probably just best be accomplished by downloading the whole database, or (less optimally) using PIR to probe for the locations of single BSSIDs.

Re: Nearby peer discovery without GPS using environmental fingerprints

#24

Earlier quoted context omitted.

Thanks for the heads up! Good to know what's out there. Interesting that I independently arrived at something possibly similar.

>Good to know what's out there. It opens you up to legal risk for knowingly infringing patents. If possible you never should look at a patent.

That is somewhat outdated advise post seagate: https://www.stblaw.com/docs/default-source/cold-fusion-exist...

Re: Nearby peer discovery without GPS using environmental fingerprints

#25
post #23
post #7

There are a couple of difficult cryptographic-type problems with this plan. (Which I like, by the way). I don’t think it’s privacy preserving, and I also don’t think it works well for finding shared locations as currently specified. Also, the privacy and the finding are in direct opposition to each-other, which isn’t always a comfortable system dynamic. On the one hand, a simple hash of ESSIDs near you, if you take a…

> Also, the privacy and the finding are in direct opposition to each-other, which isn’t always a comfortable system dynamic. ... or some sort of group key sharing Perhaps you might consider a pinsketch in the manner proposed for cryptographic biometric security. https://arxiv.org/abs/cs/0602007 I contributed to a fast implementation of the underlying algorithim: https://github.com/bitcoin-core/minisketch With it two…

Oooh, this is very interesting and timely. Thank you, reading it now.

Out of curiosity, what's the motivation for Bitcoin-Core? Is it comparing mempool txs?

Re: Nearby peer discovery without GPS using environmental fingerprints

#26
post #23

Earlier quoted context omitted.

> Also, the privacy and the finding are in direct opposition to each-other, which isn’t always a comfortable system dynamic. ... or some sort of group key sharing Perhaps you might consider a pinsketch in the manner proposed for cryptographic biometric security. https://arxiv.org/abs/cs/0602007 I contributed to a fast implementation of the underlying algorithim: https://github.com/bitcoin-core/minisketch With it two…

Oooh, this is very interesting and timely. Thank you, reading it now. Out of curiosity, what's the motivation for Bitcoin-Core? Is it comparing mempool txs?

Transaction relay.

Ideally nodes have lots of connections so that attackers can't so easy block transaction and block propagation and censor information. But lots of connections means lots of network bandwidth wasted relaying redundant information nodes already know about.

From day one bitcoin relayed transactions by offering just their hashes and only requesting what wasn't known. But even sending hashes ends up being a lot of data in total, and the bandwidth scales with peers*transactions. Using set reconciliation changes that to more like peers+transactions.

When using setrecon for authentication its important that the scheme is as close to information theoretically optimal as possible-- which makes approaches like pinsketch important.

For the transaction case faster but less communications efficient methods might be better except that latency is also a consideration for Bitcoin and minimizing latency means running reconciliation often. This stresses the inefficiencies of alternative tools as well as covers up for the quadratic decode cost of pinsketch.

I'm not aware of anyone using our minisketch library for authentication-ish uses but I'd be interested in seeing it.

Re: Nearby peer discovery without GPS using environmental fingerprints

#27
post #3
post #2

I've noticed many metro systems in cities do somehow receive GPS and cellular networks which I'm always impressed by. London on the other hand, has only recently started receiving signal for cellular networks, and rollout is slow. GPS does not work at all. I've always thought using the WiFi access points that have been installed on the underground could be a great addition to something like Citymapper to figure out w…

Phones already use WIFI for location.

Yep, you could actually fool phones into thinking they were somewhere else by just cloning a couple of ssids from another place (around 2014 iirc). I dont think this works anymore since phones now use multiple gnss bands etc. That said, my phone thinks its at my home station for the whole 20km’s ride underground, while 5g connectivity is excellent and i have wifi and gps turned on (edit, using Apple Maps).
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