Interesting. Everyone seems so sure that DP-3T (the protocol that Google and Apple are adopting for their API) will work sufficiently well that the use of the PEPP/ROBERT protocol which is being used by NHSX, the French, and the Italians will be unnecessary. Since DP-3T discloses less information about your social graph to the central party (although in some edge cases more about your social graph to everyone in the network) this would mean that DP-3T is superior.
Clearly if they both work well, then the one that discloses less data is better.
It is important that we maintain context here: these are both "minimally disclosive" protocols which were designed to transmit as little information as possible while being effective tools. Compare this with the absolutely pervasive tracking being done in South Korea and other places. The difference is that NHSX and the designers of PEEP/ROBERT thinks that a higher level of disclosure is required than DP-3T to be effective. At the moment, we do not know if either of these will work, so it's not the case that we can say: "they both work, therefore only a surveillance state would pick the one that discloses more information". It is a balance and that will always lead to different people making different decisions.
I suspect we will know this week whether the app as currently setup will work from the IoW trials. If it doesn't work, kills the battery, etc. then I hope NHSX has a DP-3T alternative in the background. Given current levels of infection in the UK, this will become important in the last week of May onwards for releasing lockdown measures so they have a few weeks to get a solution that works.
Further more, any contact tracing app that uses a technological solution is limited in its usefulness anyway. Viral transmission is not well modelled by radio packet transmission. Bruce Schneier has views on this [1], as do the Uni of Cambridge Digital Research team who consulted on the NHS app [2].
In fact, this is a benefit of the centralised matching model proposed by the NHS. The algorithm, eg number of packets received, time window in which they are received, can be tailored to improve the model.
But in any case, using Bluetooth to model virus transmission risks becoming a massive red herring.
True. Jonathan Van-Tam was saying in the daily briefing a few days ago that they are definitely not relying on this as a magic bullet, there will have to continue to be substantial old school manual contact tracing.
I think if we did know exactly the mechanics of transmission then we could afford to be super minimalist about how much data was disclosed and restrict it only to the very least required. The problem is that we don't know what that minimum is. I think one difference between critics of this approach (and indeed Google/Apple) and the NHSX/Ministerial decision makers here is that the former are not accountable for controlling transmission. If it doesn't work then they tried to help and regrettably it didn't work. The latter are trying to thread a course between how many people will die, how many years we'll be paying off debt or suffering from economic chaos, and privacy implications. That doesn't mean we can just ignore the latter, that is too easy and only leads in one direction, but it also means that decision makers have to balance competing concerns.
If it were me (but I am neither an expert nor do I have the full set of data that they do) I would pursue the same course as they are but also have a team working on an alternate implementation as a plan B. I would also make binding public commitments about what we would do with this data, introducing new statute law if really required. Again though, that's easier said than done because they don't yet know exactly how they'll need to use this data.
Great comment, nice to see some rational/balanced thinking on this.
To me it seems overly paranoid to suggest that the UK government would be doing this merely so they could track citizens movements or whatever - and I'm pretty sure the intelligence services are capable of doing that already if they want to. There are definite upsides to their approach from a surpressing the infection point of view, obviously they believe they are worth the trade-offs.
It will be interesting to see how the trial plays out vs. other countries using the Apple/Google approach. I don't think the government would risk having another potential large failure in handling this crisis if the evidence clearly points to the Apple/Google approach being better.
I did see a quote yesterday to the effect that nothing is set in stone and they can change the approach they are using if necessary, can't find the source right now.
> To me it seems overly paranoid to suggest that the UK government would be doing this merely so they could track citizens movements or whatever
I agree, but don't ignore the rest of the argument, which is that the beta versions of the app failed the requirements to be included in the NHS App library; they're using weird version control so NHSX can't do correct tests on the app; it's already failed some security testing; and the contract was awarded to someone on Sage, who has a brother that works for Cummings.
The HSJ article really looks like it is both written by and sourced from people who are not too close to either this process no to software development.
I would expect at least some beta versions not to pass all tests, it is not even clear whether they have submitted it for formal testing yet.
They're not using "weird version control", they're using continuous release during development which is totally standard. They'll have to switch to version numbers and formal change control once they enter the NHS Digital approval process but I don't think they have yet.
NHSX is delivering the app. Faculty (which is run by Marc Warner) has other government contracts but I don't think building mobile apps is really what they do.
Clearly if they both work well, then the one that discloses less data is better.
It is important that we maintain context here: these are both "minimally disclosive" protocols which were designed to transmit as little information as possible while being effective tools. Compare this with the absolutely pervasive tracking being done in South Korea and other places. The difference is that NHSX and the designers of PEEP/ROBERT thinks that a higher level of disclosure is required than DP-3T to be effective. At the moment, we do not know if either of these will work, so it's not the case that we can say: "they both work, therefore only a surveillance state would pick the one that discloses more information". It is a balance and that will always lead to different people making different decisions.
I suspect we will know this week whether the app as currently setup will work from the IoW trials. If it doesn't work, kills the battery, etc. then I hope NHSX has a DP-3T alternative in the background. Given current levels of infection in the UK, this will become important in the last week of May onwards for releasing lockdown measures so they have a few weeks to get a solution that works.