NHS contact tracing app

[Andy Burns]

Yes, clearly they /have/ put some decent brains onto it.

if someone you've been "near" later reports that they're feeling ill, it will tell them to get tested and tell you to self isolate pending their result ... but after a few days if turns out they either weren't ill or didn't bother going for a test after all, it'll say you're ok to leave home again.

It seems to me that mechanism gives an anonymous way for people to go around "hooving up" bluetooth contacts, then falsely claiming to be ill, therby maliciously locking down the owners of the other devices at home for a few days?

[Andy Burns]

28 days it says.

[Andy Burns]

It does now, but the first few years (maybe not 5) were a bit grim.

[Jethro_uk]

Not quite.

Seems they clearly asked the decent brains for the solution, and then went out of their way to ignore every single point.

I long ago worked out the difference between "we have consulted with ..." and "we have actually paid attention to ..."

[alan_m]

Are these the same TV programmes that show a full number plate being rendered from a single pixel, and then the registration number being read from it?

[alan_m]

No it's just another way of enforcing a lock-down. You cannot leave your own house unless you have the phone with this app, and that it works.

The app could also track unnecessary journeys and automatically issue the £60 fine each time.

[Adrian]

Interesting, but something it doesn't answer.

I've played around with BLE Beacons in the past, and have a vague feel for the range on them. If I leave my phone on the bedside table overnight (which is against the party wall), and next door does the same, are our phones going to log each other as a close contact, lasting several hours, even though we've not been in anything resembling close contact ?

Adrian

[Chris B]

Yes but a lot of people (anybody with a fitbit wrist band and I suspect many other brands) will have BT on all day anyway. I certainly don't notice a significant penalty on battery life of having BT on all day.

[Andy Burns]

I would say yes, my tablet sees a TV, a fitbit and a laptop as unpaired devices (I know the latter is from my non-attached neighbour, I suspect the first two are from the attached neighbour).

[Chris B]

That too is an interesting read. I thought the headline a bit disingenuous "asks for your location" to most headline skimmers would mean GPS records, but in fact its just the first half of your home postcode, which is hardly your location.

Some of the other issues about not working if both phones are asleep or keeping the phones awake and unlocked permanently must surely have been issues resolved during the alpha testing.

If they are genuinely are still issues I can't see it being useful but perhaps the thinking/modelling is that it may not get 100% of the possible at risk contacts but x% (where X is some figure less than 100) would be enough to make it useful for the purpose.

[Chris B]

Bearing in mind that they are looking for something like 2m distance I would have thought they would be looking for a very strong BT signal. Would the party wall not attenuate the signal to such an extent that signal level would indicate 10m (or so) separation, even if in fact it is only the depth of the party wall/

[AJH]

Whether it can be tracked in real time by the police or not the phone will be camped on one or more cell toweres at any time, these tend to have 4 directional antenna and 64 IIRC time slots which are allocated the phone depending on its distance from the tower so that should narrow it down to a segment and radius fairly accurately.

[Dave Liquorice]

Thought I saw somewhere that it takes a couple of days from installation to become "active". Assumed that was to work out which devices it saw a lot of and therefore likely to be same household and thus not particulary relevant.

There really does need to be a proper technical explanation of what this app actually does. Some arty farty dummed down version for the masses isn't good enough.

From several descriptions of it a "contact" is not logged unless the two devices spend longer than 15 minutes closer than 2 metres. So why are worried about super markets when your not going to spend more than a minute within 10 metres of another shopper.

[Chris B]

Well the document I linked before does reference to the privacy and security design. (Although it does come with the caveat that

"It?s imperfect and not even complete (sorry!) but we thought it was better to get something out rather than wait to make it perfect."

[Adrian]

In message <r8s85c$jmv$ [e-mail], Chris B [e-mail]> writes

One of the BT devices that I spotted up was a Firestick, and from the name of it, I know that it was at the far corner of (attached) next doors house, rather more than 2M. Like wise, at one point I had a BLE beacon sat in my car, and I could "see" that at over 10M. I never worked out how to detect the range of the beacon, so I don't know how much attenuation there was as it passed through several walls and other household clutter.

Something else that may be significant, whilst playing around with the beacon, at times something (I don't know what) was effectively blocking the signal, even when I had the beacon next to the detector (a PI 3). If that is still happening, then it could screw up anything else trying to use BT.

Adrian

[alan_m]

Surely it only takes seconds to transfer the virus and it's practically impossible to keep 2 metres apart in a supermarket all of the time. During lockdown I've been to my local supermarket twice with people just standing in the isles for many minutes trying to decide what to buy with people who don't want to be out too long, or know exactly what they want, passing by these people within a foot. Where supermarket checkout queues with people two metres apart extend down the isles other shoppers travelling down those isles are also passing in very close proximity. Doesn't any such tracking/tracing app need to log every close proximity encounter irrespective of the duration?

Is there enough repeatable definition in the Bluetooth signal strength to establish, say, 10cm , 2 metres and 10 metres separations. What happen with a signal from someone travelling the opposite direction in a passing car?

What is the positional accuracy from cell tower? 50m? What is the positional accuracy from GPS in a building without a clear view to the sky? My phones' GPS performs rather badly when the phone is in my house away from any windows.

[Joshua Snow]

It isnt a tracking feature, ALL it does is keep track of is which phones you have been close enough to for long enough.

[Dave Liquorice]

which

If I did it's bollocks according to the document below...

Good read even if all the encryption stuff went whoosh. It tells us what is collected what is stored and for how long (though not what happens to any data uploaded).

[Dave Liquorice]

intervention

The NHSx app yes, but what does the Google/Apple decentralised system do?

[bert]

It's a low energy version of BT.