One Billion Apples’ Secret Sauce: Recipe for Apple Wireless Direct Link Protocol | Hacker News Reader

One Billion Apples’ Secret Sauce: Recipe for Apple Wireless Direct Link Protocol

arxiv.org

145 pointsjonashoechst44 comments

"We have found that AWDL connections do not feature any security mechanism. All action and data frames are sent in plain and without authentication. AWDL delegates security functions to the transport and application layer, e. g., AirDrop uses TLS 1.2. The approach appears to be an informed decision to implement application dependant[sic] policies: a device might be trusted for sending an image file via AirDrop, but not for remote-controlling a Keynote presentation."

For that matter I don't like interference on the crowded WiFi bands.

It seems some creep uses AirDrop to send some lewds to somebody else on a plane every other week.

I want to know my mac is using my wired and wireless network the way I intend rather than degrading the performance of WiFi, Bluetooth, ZigBee, Z-Wave, and other protocols that keep piling into unlicensed airspace.

To be clear, this feature is standards-compliant WiFi. It uses standard 802.11 frames and leverages the vendor-specific features to allow custom payloads. It’s not “degrading the performance” of WiFi - it is WiFi.

Unlicensed spectrum is limited. There are just three channels in the 2.4 GHz, and not really more than in the 5 GHz band because most of the 5 GHz band is occupied by weather radar and you can only use that spectrum if you pay the patent trolls for the coexistence technology specified by law.

When you turn on a WiFi analyzer program and see many WiFi networks using the same spectrum, there is interference. It isn't that it "stops working" but you will get packet loss, reduced data transfer, etc. Every printer that sets up its own AP, every phone that is a hotspot, is interference.

If you want and really use these services that is one thing, but it is insane that people use WiFi to print at a mall store when they could hook up the printer to the register with a 6 foot cable.

The article itself shows a substantial degrade of WiFi performance on the Mac itself because the mac is momentarily disconnecting from the real network to stay synchronized with the lewds network.

The degradation happens only when you explicitly start using a service (such as AirDrop) that uses AWDL. The AWDL interface becomes inactive once there is no more traffic on the interface. In the measurements, we show the performance when both infrastructure and AWDL traffic is present (i.e., the Wi-Fi radio needs to switch channels in between).

In fact one could argue that AWDL actually reduces "interference" because two neighboring devices can communicate directly and do not need to go an additional one-hop detour over an access point.

What interference? It sounds like this is using vendor extensions to the 802.11 Wi-Fi standard.

I have no idea what the default for AirDrop is, I keep it open only for contacts. If it’s open by default everyone that’s crazy. Doesn’t sound like the kind of thing Apple would do today, although it wouldn’t surprise me if it was like that in the past.

> I want to know my mac is using my wired and wireless network the way I intend

Which it is, you can have AirDrop on or off and to accept connections from everyone or just your contacts. All modes have their uses.

Sounds like you should just turn off AirDrop.

One neat application is sharing WiFi passwords— I was recently at a friends place and when I went to sign in to their home WiFi on my iPhone I believe they got a pop up on their phone saying “share password with xyz’s iPhone?” And the whole thing was super seamless, with no need for them to look it up and no need for me to type it in.

so in the future - you can "war pop-up" random wifi's owners - by simply attempting to connect to the wifi and forcing a pop-up that says "Share wifi password with 'Save 15% of Geico's iPhone?"

No. It only works when you have each other within your Contacts list.

https://www.macrumors.com/how-to/share-your-wifi-password-wi...

So are they tracking your contacts or can you spoof it from your phone? If one is not possible the other should be.

On iPhone you have an iMessage acccount which is tied to the phone number. It can be done on the device, so it probably is.

Still waiting on an AirDrop client for non-Apple products. It works really well and is pretty convenient. Maybe this paper will help.

It really is just one of those things that works so well. I was traveling recently and met some folks at a hostel. At the end of the trip we wanted to share our photos and videos with each other. Our hostel's internet connection consisted of a weak wifi access point, connected to weak satellite internet, with dozens of people vying with each other for the available bandwidth.

One of us suggested AirDrop and we sent dozens of photos and videos between us within a few minutes time. Maybe this seemed more impressive to me, after several days of suffering a terrible internet connection. It definitely stood out for me as being one of those moments where technology can make things easier and magical.

I do wonder if there are patents on this, and if that has prevented other devices from adopting this kind of protocol?

I do wonder if there are patents on this, and if that has prevented other devices from adopting this kind of protocol?

WiFi has always had AdHoc mode which enables two devices to directly communicate like they were on the same Ethernet link, and I've used it a few times for a similar use-case to yours. It seems AirDrop is just a layer on top of that which facilitates the configuration required, but otherwise it would probably not be too difficult to "roll your own" similar app.

AirDrop can also use BT. I think it decides based on file size? Either way I imagine BT is used to help negotiate everything instead of just connecting to dozens of random ad-hoc networks.

Aren’t many devices limited to one WiFi network (whether ad-hoc or infrastructure) at once? That would mean many devices couldn’t do this without breaking normal WiFi.

Doesn't Ad hoc force you to disconnect from your current Access Point? I'm under the impression that this is not the case with Air Drop.

This is why AirDrop only works on some newer hardware: It requires Wi-Fi interfaces which can do Ad-Hoc and Infrastructure mode simultaneously.

Yes, unless your AP and ad hoc networks are on the same channel, you need two Wi-Fi radios to support this. AWDL "solves" this problem by quickly switching between these channels and schedules frame transmissions when the radio is tuned to the correct channel so the operation is (almost) transparent for the user (obviously, you loose some airtime for channel switching and your average latency increases).

Most cards nowadays support at least one ad-hoc and one infrastructure connection. Sometimes they have to be on the same frequency though, but it certainly wouldn't be hard for Apple to just buy one that supports multiple frequencies.

Not in most cases, but it is somewhat chip (and driver) dependent).

Miracast is another example of this - In most cases you can remain connected to your main network connection via Wi-Fi but also use Wi-Fi direct to run a casting session.

I've had the opposite experience with air drop... It's never worked for me even with a fair amount of tinkering. I end up just running an ssh server and scping stuff around...

Never really had an issue with it, even use it to send my details to others for contacts. Faster than handing phones around, and people then start sending me "happy birthday" texts as my contact info has that junk in it.

It depends on the user community and when.

Some of the older devices don’t support it, or people aren’t signed into iCloud or have a problem with their sign-in.

Little things like this add up to the whole customer experience which is, I believe, what they see as their competitive advantage. I don’t see a supported client coming any time soon.

Zapya is one of the apps that almost everyone in SE Asia seems to have on their phones for transferring files back and forth in the absence of wifi networks. From what I could tell it is the primary way that music and photos are shared in Myanmar. It’s clunkier than airdrop, but x-platform.

And I am waiting for iMessage to come to other platforms just like Apple Music on Android [1].

Even a basic Android app would do and I think it's perfectly fine if one can have an iMessage account on other platforms iff they have at least one Apple product with "Messages" app on it - an iPad, a Mac, or an iPhone etc.

It's a pretty good messaging service but almost useless to me (and I am sure to a lot of people) because very few among my friends have iPhones but a hell lot of them have Macs - like really a lot!

[1] https://play.google.com/store/apps/details?id=com.apple.andr...

I still have openairdrop.org available to link to the first open source project to implement this protocol.

Man it would be great to have an Android implementation. I like my MacBook running osx but I don't like iPhone hardware

Or lack of real software ownership e.g. no root allowed!)

There is not a lot of software on my phone I would care about “owning.” I am not writing code on my phone; I am using it for routine tasks. I don’t have a need to dig into the internals and the “benefits” of doing that are overshadowed by the security risks.

I am not sure that's the best example ..

Not being able to install any software without Apple acting as the middleman is very concerning for both 3rd party devs and consumers.

But that should not be something that has anything to do with root.

FWIW, Android does this better : you do have a play store but you can also sideload any app. You just need to confirm that you know what you are doing and the play store can still scan these apps against known malware signatures.

Wow. No love. Isn't lack of root like buying a house but the builder refusing to give you a master key or permission to change the locks?

I would say it's more like seller not allowing you to dig the whole house inside out and build one from scratch by choosing the size of brick, how much they were baked, brand of cement used and all that. Like they do not allow something like this in gated communities/apartments.

99% of Apple consumers think root is something that grows out of the bottom of a tree.

Are you sure you don’t mean 99% of all phone or computer users do not know what root means?

Interestingly, they seem to based some of their research on the leaked source code for a Broadcom driver, which has now been taken down. So much for reproducible research, I guess?

Nice, I really wish this protocol would be available for Android as the number of applications would be immense (Apple's Multipeer Connectivity Framework).

But it looks like Apple will deprecate this sooner or later, since they have joined The Thread Group [1]

[1] https://www.macrumors.com/2018/08/07/apple-thread-group-smar...

I really don’t see Thread as being in the same ballpark as AWDL - they have very different goals and use cases.

Air drop is fast for sure.

Feature request: make it work the same when you share videos and photos via messages or photos app.

Could you describe your feature in more detail? I am interested in what you are asking, but I don’t think I understand clearly.

Url changed from https://owlink.org, which points to this.

Secret apple sauce?

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