NZ COVID Tracer app for Android and iOS

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#2527071 22-Jul-2020 13:05

MurrayM: I believe they contain a JSON structure of a few hundred characters) they need to be displayed optimally in order for the scan to work.

And therein lies the problem. They could probably get away with a v10 code (all they need is a store ID/business ID), which would be the easiest/most reliable to scan, but instead they go for the innately difficult-to-scan option.

The MoH app and its deployment is starting to look like a design example of how not to do something like this. Almost everything you can get wrong, they've got wrong. I can understand a few problems here and there, but not this end-to-end fail.

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#2527085 22-Jul-2020 13:24

neb:And therein lies the problem. They could probably get away with a v10 code (all they need is a store ID/business ID), which would be the easiest/most reliable to scan, but instead they go for the innately difficult-to-scan option.

It's not toooo long a string. But it is why I'm strong for encouragement to use a standard barcode scanner and double check. Cause it looks more and more by the time it takes me to scan the A4 (if it even does.. looking at you 'Z') vs the A3 - the shops are perhaps scaling down and hiding A4s because Head office has told them to do one, rather than make it super obvious and easy for the camera to decode.

https://www.geekzone.co.nz/forums.asp?forumid=161&topicid=270639&page_no=15#2492574

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#2527086 22-Jul-2020 13:29

ezbee:

Would the scanning problems be they are trying to pack too much data into the poster ?
Developers have all the best kit and never accounted for poorer cases , to have a robust solution.
How much data would you really need for unique id f?
Lower data density also allows more room for error correction and coarser codes easier to read under challenging circumstances.

A Munzee QR code contains a URL that uniquely identifies the Munzee. An example of a Munzee URL is: https://www.munzee.com/m/TheBitBandit/4158/927MOC/

The URL contains my Munzee username (TheBitBandit), a Munzee number that is unique to my username (4158) and a randomly generated secret code (927MOC). This Munzee QR code looks like this:

This is all that the Munzee app needs to uniquely identify the individual munzee and verify that I've found it. As you can see Munzee QR codes look a lot simpler than the Govt QR codes.

I've had a read of the MOH's official QR code spec and it looks like they're using Version 13 codes. An example of what they're storing in the QR code is:

{
"typ":"entry",
"gln":"0000000000000",
"opn":"Kaikōura Souvenirs and Gifts",
"adr":"Level 1\n123 Main Street\nKaikōura",
"ver":"c19:1"
}

So they're storing a lot more than a simple unique ID, which means they've had to go for a higher QR code version number in order to fit all that data in. I'd say they were going for maximum flexibility in designing the structure, which may have sacrificed some robustness with the actual scanning.

In perfect conditions (poster is perfectly flat, good lighting, no damage to the code, scanning straight on and not at an angle, etc) the Govt's codes scan just fine, as evidenced by the fact that I was able to scan the ASB's poster and also the North Harbour Gymnastics Mini Gym at the Glenfield Mall (both scanned in 1-2 seconds). But as can be seen from the Glenfield Countdown example it doesn't take too much to make the code difficult to scan.

richms

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#2527431 22-Jul-2020 19:24

Probably because the tinfoil hat idiots want it to run offline because otherwise people might get tracked. Ruined the whole idea of it to satisfy a few edge case people.

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neb

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#2527510 22-Jul-2020 23:13

MurrayM:
I've had a read of the MOH's official QR code spec and it looks like they're using Version 13 codes.

And that's the problem, the tail is wagging the dog in that design. Instead of saying "we'll aim for the most reliable, easy-to-scan code there is and adapt the data accordingly", they've said "we'll stuff a bunch of redundant JSON in there and have to use a hard-to-scan-reliably code to handle it all".

If you don't mind an online lookup, you need (say) 32 bits to map a unique business ID to its name and address, what's currently in the JSON. If you want to encode the entire address in the code itself you can use dictionary compression and variable-length coding and get it into maybe 80 bits. You couldn't get every obscure address, but for the 0.1% that can't be encoded in 80 bits you could use the harder-to-scan more complex QR codes. So go for minimum complexity, maximum error correction, and you've got the best chance of everything being able to scan the code.

MurrayM

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#2527565 23-Jul-2020 08:33

neb:
MurrayM:

I've had a read of the MOH's official QR code spec and it looks like they're using Version 13 codes.

And that's the problem, the tail is wagging the dog in that design. Instead of saying "we'll aim for the most reliable, easy-to-scan code there is and adapt the data accordingly", they've said "we'll stuff a bunch of redundant JSON in there and have to use a hard-to-scan-reliably code to handle it all". If you don't mind an online lookup, you need (say) 32 bits to map a unique business ID to its name and address, what's currently in the JSON. If you want to encode the entire address in the code itself you can use dictionary compression and variable-length coding and get it into maybe 80 bits. You couldn't get every obscure address, but for the 0.1% that can't be encoded in 80 bits you could use the harder-to-scan more complex QR codes. So go for minimum complexity, maximum error correction, and you've got the best chance of everything being able to scan the code.

Indeed, a smallish unique ID would have been much better from the point of it resulting in a much simpler QR code that would have a higher chance of being able to be scanned successfully in non-optimal conditions. They would have needed to have a central database to match each unique ID with it's actual location and to update that database as each QR code is generated for the posters. I don't know if they have a DB like that for the current system, maybe they were trying to avoid that by stuffing as much info into the QR code's JSON structure as possible?

neb

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#2527812 23-Jul-2020 14:29

MurrayM:
maybe they were trying to avoid that by stuffing as much info into the QR code's JSON structure as possible?

I doubt they even thought about it, if they were worried about space they (a) wouldn't have used JSON and (b) wouldn't have added a pile of completely useless fields that do nothing that bloat up the data size. Even if they don't want to do a central DB, and given that everyone who applies for a QR code gets recorded it's not like they don't have the info anyway, you could encode the vast majority of NZ addresses into about 80 bits from a back-of-the-envelope calculation.

The whole thing looks like a project carried out without any stakeholder involvement at all. The fact that the peanut gallery here has already come up with dozens(?) of no-brainer improvements indicates just how poorly thought-out it was.

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#2527826 23-Jul-2020 15:24

I wish they would just hurry up and enable bluetooth tracing using the official bluetooth covid API's in Android and iOS! Can't be bothered scanning codes everywhere.

Technofreak

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#2527967 23-Jul-2020 21:45

Yabanize:

I wish they would just hurry up and enable bluetooth tracing using the official bluetooth covid API's in Android and iOS! Can't be bothered scanning codes everywhere.

How does the Bluetooth option work? Is dependant on phone settings? If so I'd suggest that's will be ass useful as the current app.

Actually from what I understand of the current app if it it is ever implemented properly and promoted well it is the best solution.

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Oblivian

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#2527973 23-Jul-2020 21:50

Technofreak:

How does the Bluetooth option work? Is dependant on phone settings? If so I'd suggest that's will be ass useful as the current app.

Actually from what I understand of the current app if it it is ever implemented properly and promoted well it is the best solution.

https://www.google.com/covid19/exposurenotifications/

MoH could chose to re-launch another which hooks the API. Or integrate. Needs min Android 6

Random ID, looks for pairs. But of course everyone will still be convinced it's tracking them (more than the social media they just checked in on or got near a known WiFi point...)

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#2527980 23-Jul-2020 22:35

Looks like it's probably dependant on phone settings. Also Android 6 or later might be a bit limiting.

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freitasm

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#2528003 24-Jul-2020 07:45

Remember that any app that needs to be running in the background will utterly fail on Android - different OEMs make their own rules for "battery saving".

Oblivian

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#2528014 24-Jul-2020 08:38

And that was one of the PM's talking points at one stage.

If the user want's it, they wan't it automatically

BUT they don't want to be 'tracked'

If a user experience or device is impacted as a result - they'll stop or uninstall it or find a way that defeats the purpose

BUT they don't want to manually have to do anything

It's like a scene out of Matrix. Me me ME ME ME!

Rather than I and everyone, I and everyone, I and everyone

MurrayM

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#2528024 24-Jul-2020 09:27

freitasm:

Remember that any app that needs to be running in the background will utterly fail on Android - different OEMs make their own rules for "battery saving".

This is so true. I had to get a new phone recently and opted for an Oppo A5 2020. For the first few days I was wondering why I seemed to be not receiving some notifications, or I was getting them but they were delayed (text messages, Gmail notifications, IFTTT, etc). After some digging I found people reporting that Oppo used very aggressive power management to make their batteries last longer (I'm not sure if this is on all Oppo models or if I was just unfortunate enough to get it on mine). After I turned off "Smart Restriction of Background Running" for a bunch of apps I found that things mostly now work as I expect. I've never had this problem on other Android phones I've owned and I certainly wouldn't expect the average user to know about this or spend any time investigating it; they'd probably just blame the contact tracing app as not working.

Also, it seems that tracking via bluetooth wouldn't help you in the situation where an infected person visits a cafe and sneezes all over a table and then leaves, and I come along 5 minutes later and sit at the same table and pick the virus up from the table surface. Since I was never in the same space as the infected person at the same time our phones wouldn't have exchanged anything.

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#2528027 24-Jul-2020 09:42

You haven't experienced the Huawei aggressive power management... This is the only way Android can have any battery life.

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