site_archiver@lists.apple.com Delivered-To: bluetooth-dev@lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:message-id:mime-version:subject:date:in-reply-to:cc:to :references; bh=FkqGwId1E6MvbIQ7RKay1Kv8gvzYP4L8abD1zGa5Lto=; b=aG5GLjl3OVk4DN4lRbo3bM8J/aOtWQu7xDFn/Asyh187biqCd4k4Pj/NXcR+lfvGFa qo+S19qWNR/CvRavL/PLGXrfdnnpPe5HSvljIRxqYSE3rwajfZ0HV1QMZ7Rq6NAADuyR F2Nv+ubUUkA3yGR3tFf+/2qAODaPaOclylYnq8LbtQUBN4+00Qlrd+B8me49gpcSS7mp Ue2WCkT1kKvQuZFshSe5Btd0Z5IWqyq46GzBzww5wd+g6ri2PoJeMS8LCB226+eDNGVS /ziFC+s3xo3/qp+weBgS/6liBtq/6dZkp8dp4o1ntcwGngo/32i05bSzngK2nUF5n4ID IDcQ== I’ve been playing around with this today, testing with my own code and looking at the NHS App. The NHS App is doing nothing special, as far as I can see It advertises a service, and in the background iOS puts the service in the “overflow” (one-hot encoded <https://crownstone.rocks/2018/06/27/ios-advertisements-in-the-background>) Android looks for this specific one hot encoded value. Actually, it doesn’t look for a specific bit set, but a fixed set of bytes, so if other Apps are advertising services in the background on iOS the NHS App on Android might fail to discover it. This seems like a bug, although I’m not sure if they could work around it It attempts to keep connections (and the process) alive for as long as possible by sending “keep alive” data every 8s (under the 10s execution window apple provides) It is susceptible to the problems other Apps are (restarting the phone, quitting the app etc can break scanning and discovery) but it helps to overcome this through notifications to the user to reopen the app. I’m not sure if Apple imposes a time limit on scanning for/advertising services in the background although presumably there is a notification for this in the NHS App if it does. With the user notifications, if users actually respond to them it might work well enough to be effective. But I could see users ignoring the notifications if there are too many, and particular when out and about and busy these may get ignored. If they are ignored, the App may not work for a long period of time. It seems the UK government may be reconsidering the centralised approach now anyway: https://www.telegraph.co.uk/news/2020/05/06/nhs-explores-feasibility-moving-... <https://www.telegraph.co.uk/news/2020/05/06/nhs-explores-feasibility-moving-contact-tracing-app-apple-google/?fbclid=IwAR2qT77qzPkMlefQWYRFKmy-zj3Y_z2-Ip2peuUE9nCdokHldxuEIC1Ze64> I’d be keen to hear any further insight into how the App is working or background bluetooth can made to work better. Nick Brook NRB Tech W: https://nrbtech.io <https://nrbtech.io/>

On 7 May 2020, at 21:17, Darren Jones via Bluetooth-dev <bluetooth-dev@lists.apple.com> wrote:

There is no location permission in the app. Which is a good job as the questions over privacy would explode more than they already have.

Sent from my iPhone

...

On 7 May 2020, at 21:14, Diego Alfarache <dalfarache@gmail.com> wrote:

 These apps are going to have background location permission, which effectively gives them free reign to run almost anything in the background.

I created a framework for a client that would act as both a peripheral and central while executing in the background, but only when they had “always” location permission.

Diego

From: "Jan Lübeck via Bluetooth-dev (Fyrastudio)" <bluetooth-dev@lists.apple.com> Reply-To: "Jan Lübeck (Fyrastudio)" <jan@fyrastudio.com> Date: Thursday, May 7, 2020 at 3:04 PM To: Darren Jones <djonesuk@me.com> Cc: <bluetooth-dev@lists.apple.com> Subject: Re: Background CoreBluetooth

Apple did announce that they are sharing their APIs with specific developers. Maybe UK NHS is one of them? ______ Jan Lübeck Chief Technology Officer fyrastudio.com <http://fyrastudio.com/>

On Thu, May 7, 2020 at 3:48 PM Darren Jones via Bluetooth-dev <bluetooth-dev@lists.apple.com <mailto:bluetooth-dev@lists.apple.com>> wrote: Unless you have your head buried in the sand, I’m sure everyone has noticed the sagas going on with countries creating their own COVID-19 contact tracing apps.

I have personally tried many times over the years to create an app that can broadcast and scan in the background to trigger a ‘contact trace’ and always failed. Yet the UK NHS are claiming they have an app that does just that.

I’d love to hear from anyone that’s had experience with background BT. Is it possible? Can a background CBPeripheral be detected by a background CBCentral?

If not, is there a definitive time period when discovery becomes impossible?

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