To achieve full-stack Software Freedom on mobile phones, I think it makes sense to
Back in August, I listened to an episode of the Free as in Freedom oggcast that included a FOSDEM 2013 talk by Aaron Williamson titled “Why the free software phone doesn’t exist”. The talk actually didn’t include much discussion of the driver situation and instead devoted a lot of time to talking about services that phones connect to and the interaction of the DMCA with locked bootloaders.
Also, I stumbled upon the Indie Phone project. More on that later.
Looking at existing systems, it seems that software close to the hardware on mobile phones tends to be more proprietary than the rest of the operating system. Things like baseband software, GPU drivers, touch sensor drivers and drivers for hardware-accelerated video decoding (and video DRM) tend to be proprietary even when the Linux kernel is used and substantial parts of other system software are Free Software. Moreover, most of the mobile operating systems built on the Linux kernel are actually these days built on the Android flavor of the Linux kernel in order to be able to use drivers developed for Android. Therefore, the driver situation is the same for many of the different mobile operating systems. For these reasons, I think it makes sense to separate the discussion of Software Freedom on the driver layer (code closest to hardware) and the rest of the operating system.
For software above the driver layer, there seems to be something of a default assumption in the Free Software circles that Replicant is the answer for achieving Software Freedom on phones. This perception of mine probably comes from Replicant being the contender closest to the Free Software Foundation with the FSF having done fundraising and PR for Replicant.
I think betting on Replicant is not a good strategy for the Free Software community if the goal is to deliver Software Freedom on phones to many people (and, therefore, have more of a positive impact on society) instead of just making sure that a Free phone OS exists in a niche somewhere. (I acknowledge that hardline FSF types keep saying negative things about projects that e.g. choose permissive licenses in order to prioritize popularity over copyleft, but the “Free Software, Free Society” thing only works if many people actually run Free Software on the end-user devices, so in that sense, I think it makes sense to think of what has a chance to be run by many people instead of just the existence of a Free phone OS.)
Android is often called an Open Source system, but when someone buys a typical Android phone, they get a system with substantial proprietary parts. Initially, the main proprietary parts above the driver layer were the Google applications (Gmail, Maps, etc.) but the non-app, non-driver parts of the system were developed as Open Source / Free Software in the Android Open Source Project (AOSP). Over time, as Google has realized that OEMs don’t care to deliver updates for the base system, Google has moved more and more stuff to the proprietary Google application package. Some apps that were originally developed as part of AOSP no longer are. Also, Google has introduced Google Play Services, which is a set of proprietary APIs that keeps updating even when the base system doesn’t.
Replicant takes Android and omits the proprietary parts. This means that many of the applications that users expect to see on an Android phone aren’t actually part of Replicant. But more importantly, Replicant doesn’t provide the same APIs as a normal Android system does, because Google Play Services are missing. As more and more applications start relying on Google Play Services, Replicant and Android-as-usually-shipped diverge as development platforms. If Replicant was supposed to benefit from the network effects of being compatible with Android, these benefits will be realized less and less over time.
Also, Android isn’t developed in the open. The developers of Replicant don’t really get to contribute to the next version of AOSP. Instead, Google develops something and then periodically throws a bundle of code over the wall. Therefore, Replicant has the choice of either having no say over how the platform evolves or has the option to diverge even more from Android.
Instead of the evolution of the platform being controlled behind closed doors and the Free Software community having to work with a subset of the mass-market version of the platform, I think it would be healthier to focus efforts on a platform that doesn’t require removing or replacing (non-driver) system components as the first step and whose development happens in public repositories where the Free Software community can contribute to the evolution of the platform.
Let’s look at the options. What at least somewhat-Free mobile operating systems are there?
First, there’s software from the OpenMoko era. However, the systems have no appeal to people who don’t care that much about the Free Software aspect. I think it would be strategically wise for the Free Software community to work on a system that has appeal beyond the Free Software community in order to be able to benefit from contributions and network effects beyond the core Free Software community.
Open webOS is not on an upwards trajectory (on phones despite there having been a watch announcement at CES). (Addition 2015-01-24: There exists a project called LuneOS to port Open webOS to Nexus phones, though.) Tizen (on phones) has been delayed again and again and became available just a few days ago, so it’s not (at least quite yet) a system with demonstrated appeal (on phones) beyond the Free Software community, and it seems that Tizen has substantial non-Free parts. Jolla’s Sailfish OS is actually shipping on a real phone, but Jolla keeps some components proprietary, so the platform fails the criterion of not having to remove or replace (non-driver) system components as the first step (see Nemo). I don’t actually know if Ubuntu Touch has proprietary non-driver system components. However, it does appear to have central components to which you cannot contribute on an “inbound=outbound” licensing basis, because you have to sign a CLA that gives Canonical rights to your code beyond the Free Software license of the project as a condition of your patch getting accepted. In any case, Ubuntu Touch is not shipping yet on real phones, so it is not yet demonstratably a system that has appeal beyond the Free Software community.
Firefox OS, in contrast, is already shipping on multiple real phones (albeit maybe not in your country) demonstrating appeal beyond the Free Software community. Also, Mozilla’s leverage is the control of the trademark—not keeping some key Mozilla-developed code proprietary. The (non-trademark) licensing of the project works on the “inbound=outbound” basis. And, importantly, the development repositories are visible and open to contribution in real time as opposed to code getting thrown over the wall from time to time. Sure, there is code landing such that the motivation of the changes is confidential or obscured with codenames, but if you want to contribute based on your motivations, you can work on the same repositories that the developers who see the confidential requirements work on.
As far as I can tell, Firefox OS has the best combination of not being vaporware, having appeal beyond the Free Software appeal and being run closest to the manner a Free Software project is supposed to be run. So if you want to advance Software Freedom on mobile phones, I think it makes the most sense to put your effort into Firefox OS.
Replicant, Firefox OS, Ubuntu Touch, Sailfish OS and Open webOS all use an Android-flavored Linux kernel in order to be able to benefit from the driver availability for Android. Therefore, the considerations for achieving Software Freedom on the driver layer apply equally to all these systems. The foremost problems are controlling the various radios—the GSM/UMTS radio in particular—and the GPU.
If you consider the Firefox OS reference device for 2014 and 2015, Flame, you’ll notice that Mozilla doesn’t have the freedom to deliver updates to all software on the device. Firefox OS is split into three layers: Gonk, Gecko and Gaia. Gonk contains the kernel, drivers and low-level helper processes. Gecko is the browser engine and runs on top of Gonk. Gaia is the system UI and set of base apps running on top of Gecko. You can get Gecko and Gaia builds from Mozilla, but you have to get Gonk builds from the device vendor.
If Software Freedom extended to the whole stack—including drivers—Mozilla (or anyone else) could give you Gonk buids, too. That is, to get full-stack Software Freedom with Firefox OS, the challenge is to come up with hardware whose driver situation allows for a Free-as-in-Freedom Gonk.
As noted, Flame is not that kind of hardware. When this is lamented, it is typically pointed out that “not even the mighty Google” can get the vendors of all the hardware components going into the Nexus devices to provide Free Software drivers and, therefore, a Free Gonk is unrealistic at this point in time.
That observation is correct, but I think it lacks some subtlety. Both Flame and the Nexus devices are reference devices on which the software platform is developed with the assumption that the software platform will then be shipped on other devices that are sufficiently similar that the reference devices can indeed serve as reference. This means that the hardware on the reference devices needs to be reasonably close to the kind of hardware that is going to be available with mass-market price/performance/battery life/weight/size characteristics. Similarity to mass-market hardware trumps Free Software driver availability for these reference devices. (Disclaimer: I don’t participate in the specification of these reference devices, so this paragraph is my educated guess about what’s going on—not any sort of inside knowledge.)
I theorize that building a phone that puts the availability of Free Software drivers first is not impossible but would involve sacrificing on the current mass-market price/performance/battery life/weight/size characteristics and be different enough from the dominant mass-market designs not to make sense as a reference device. Let’s consider how one might go about designing such a phone.
In the radio case, there is proprietary software running on a baseband processor to control the GSM/UMTS radio and some regulatory authorities, such as the FCC, require this software to be certified for regulatory purposes. As a result, the chances of gaining Software Freedom relative to this radio control software in the near term seem slim. From the privacy perspective, it is problematic that this mystery software can have DMA access to the memory of the application processor-i.e. the processor that runs the Linux kernel and the apps. Addition 2015-01-24: There seems to exist a project, OsmocomBB, that is trying to produce GSM-level baseband software as Free Software. (Unlike the project page, the Git repository shows recent signs of activity.) For smart phones, you really need 3G, though.
Technically, data transfer between the application processor and various radios does not need to be fast enough to require DMA access or other low-level coupling. Indeed, for desktop computers, you can get UMTS, Wi-Fi, Bluetooth and GPS radios as external USB devices. It should be possible to document the serial protocol these devices use over USB such that Free drivers can be written on the Linux side while the proprietary radio control software is embedded on the USB device.
This would solve the problem of kernel coupling with non-free drivers in a way that hinders the exercise of Software Freedom relative to the kernel. But wouldn’t the radio control software embedded on the USB device still be non-free? Well, yes it would, but in the current regulatory environment it’s unrealistic to fix that. Moreover, if the software on the USB devices is truly embedded to the point where no one can update it, the Free Software Foundation considers the bundle of hardware and un-updatable software running on the hardware as “hardware” as a whole for Software Freedom purposes. So even if you can’t get the freedom to modify the radio control software, if you make sure that no one can modify it and put it behind a well-defined serial interface, you can both solve the problem of non-free drivers holding back Software Freedom relative to the kernel and get the ideological blessing.
So I think the way to solve the radio side of the problem is to license circuit designs for UMTS, Wi-Fi, Bluetooth and GPS USB dongles and build those devices as hard-wired USB devices onto the main board of the phone inside the phone’s enclosure. (Building hard-wired USB devices into the device enclosure is a common practice in the case of laptops.) This would likely result in something more expensive, more battery draining, heavier and larger than the usual more integrated designs. How much more expensive, heavier, etc.? I don’t know. I hope within bounds that would be acceptable for people willing to pay some extra and accept some extra weigh and somewhat worse battery life and performance in order to get Software Freedom.
As for the GPU, there are a couple of Free drivers: There’s Freedreno for Adreno GPUs. There is the Lima driver for Mali-200 and Mali-400, but a Replicant developer says it’s not good enough yet. Intel has Free drivers for their desktop GPUs and Intel is trying to compete in the mobile space so, who knows, maybe in the reasonably near future Intel manages to integrate GPU design of their own (with a Free driver) with one of their mobile CPUs. Correction 2015-01-24: It appears that after I initially wrote that sentence in August 2014 but before I got around to publishing in January 2015, Intel announced such a CPU/GPU combination.
The current Replicant way to address the GPU driver situation is not to have hardware-accelerated OpenGL ES. I think that’s just not going to be good enough. For Firefox OS (or Ubuntu Touch or Sailfish OS or a more recent version of Android) to work reasonably, you have to have hardware-accelerated OpenGL ES. So I think the hardware design of a Free Software phone needs to grow around a mobile GPU that has a Free driver. Maybe that means using a non-phone (to put radios behind USB) QUALCOMM SoC with Adreno. Maybe that means pushing Lima to good enough a state and then licensing Mali-200 or Mali-400. Maybe that means using x86 and waiting for Intel to come up with a mobile GPU. But it seems clear that the GPU is the big constraint and the CPU choice will have to follow from the GPU solution.
For the encumbered codecs that everyone unfortunately needs to have in practice, it would be best to have true hardware implementations that are so complete that the drivers wouldn’t contain parts of the codec but would just push bits to the hardware. This way, the encumberance would be limited to the hardware. (Aside: Similarly, it would be possible to design a hardware CDM for EME. In that case, you could have video DRM without it being a Software Freedom problem.)
So I think that in order to achieve Software Freedom on the driver layer, it is necessary to commission hardware that fits Free Software instead of trying to just write software that fits the hardware that’s out there. This is significantly different from how software freedom has been achieved on desktop. Also, the notion of making a big upfront capital investment in order to achieve Software Freedom is rather different from the notion that you only need capital for a PC and then skill and time.
I think it could be possible to raise the necessary capital through crowdfunding. (Purism is trying it with the Librem laptop, but, unfortunately, the rate of donations looks bad as of the start of January 2015. Addition 2015-01-24: They have actually reached and exceeded their funding target! Awesome!) I’m not going to try to organize anything like that myself—I’m just theorizing. However, it seems that developing a phone by crowdfunding in order to get characteristics that the market isn’t delivering is something that is being attempted. The Indie Phone project expresses intent to crowdfund the development of a phone designed to allow users to own their own data. Which brings us to the topic of the services that the phone connects to.
Unfortunately, Indie Phone is not about building hardware to run Firefox OS. The project’s Web site talks about an Indie OS but intentionally tries to make the OS seem uninteresting and doesn’t explain what existing software the small team is intending to build upon. (It seems implausible that such a small team could develop an operating system from scratch.) Also, the hardware intentions are vague. The site doesn’t explain if the project is serious about isolating the baseband processor from the application processor out of privacy concerns, for example. But enough about the vagueness of what the project is going to do. Let’s look at the reasons the FAQ gave against Firefox OS (linking to version control, since the FAQ appears to have been removed from the site between the time I started writing this post and the time I got around to publishing):
“As an operating system that runs web applications but without any applications of its own, Firefox OS actually incentivises the use of closed silos like Google. If your platform can only run web apps and the best web apps in town are made by closed silos like Google, your users are going to end up using those apps and their data will end up in these closed silos.”
The FAQ then goes on to express angst about Mozilla’s relationship with Google (the Indie Phone FAQ was published before Mozilla’s seach deal with Yahoo! was announced) and Telefónica and to talk about how Mozilla doesn’t control the hardware but Indie will.
I think there is truth to Web technology naturally having the effect of users gravitating towards whatever centralized service provides the best user experience. However, I think the answer is not to shun Firefox OS but to make de-centralized services easy to self-host and use with Firefox OS.
In particular, it doesn’t seem realistic that anyone would ship a smart phone without a Web browser. In that sense, any smartphone is susceptible to the lure of centralized Web-based services. On the other hand, Google Play and the iOS App Store contain plenty of applications whose user interface is not based on HTML, CSS and JavaScript but still those applications put the users’ data into centralized services. On the flip side, it’s not actually true that Firefox OS only runs Web apps hosted on a central server somewhere. Firefox OS allows you to use HTML, CSS and JavaScript to build apps that are distributed as a zip file and run entirely on the phone without a server component.
But the thing is that, these days, people don’t want even notes or calendar entries that are intended for their own eyes only to stay on the phone only. Instead, even for data meant for the user’s own eyes only, there is a need to have the data show up on multiple devices. I very much doubt that any underdog effort has the muscle to develop a non-Web decentralized network application platform that allows users to interact with their data from all the devices that they want to use to interact with their data. (That is, I wouldn’t bet on e.g Indienet that is going to launch with “with a limited release on OS X Yosemite”.)
I think the answer isn’t fighting the Web Platform but using the only platform that already has clients for all the devices that users want to use—in addition to their phone—to interact with their data: the Web Platform. To use the Web Platform as the application platform such that multiple devices can access the apps but also such that users have Software Freedom, the users need to host the Web apps themselves. Currently, this is way too difficult. Hosting Web apps at home needs to become at least as easy as maintaining a desktop computer at home-preferably easier.
For this to happen, we need:
(Having Software Freedom on the server doesn’t strictly require the server to be placed in your home, but if that’s not a realistic option, there’s clearly a practical freedom deficit even if not under the definition of Free Software. Also, many times the interest in Software Freedom in this area is motivated by data privacy reasons and in the case of Web apps, the server of the apps can see the private data. For these reasons, it makes sense to consider home-hostability.)
In this case, the hardware and driver side seems like the smallest problem. At least if you ignore the massive and creepy non-Free firmware, the price of the hardware and don’t try to minimize energy consumption particularly aggressively, suitable x86/x86_64 hardware already exists e.g. from CompuLab. To get the price and energy consumption minimized, it seems that ARM-based solutions would be better, but the situation with 32-bit ARM boards requiring per-board kernel builds and most often proprietary blobs that don’t get updated makes the 32-bit ARM situation so bad that it doesn’t make sense to use 32-bit ARM hardware for this. (At FOSDEM 2013, it sounded like a lot of the time of the FreedomBox project has been sucked into dealing with the badness of the Linux on 32-bit ARM situation.) It remains to be seen whether x86/x86_64 SoCs that boot with generic kernels reach ARM-style price and energy consumption levels first or whether the ARM side gets their generic kernel bootability and Free driver act together (including shipping) with 64-bit ARM first. Either way, the hardware side is getting better.
As for the apps, PHP-based apps that are supposed to be easy-ish to deploy as long as you have an Apache plus PHP server from a service provider are plentiful, but e.g. Roundcube is no match for Gmail in terms of user experience and even though it’s theoretically possible to write quality software in PHP, the execution paradigm of PHP and the culture of PHP don’t really guide things to that direction.
Instead of relying on the PHP-based apps that are out there and that are woefully uncompetitive with the centralized proprietary offerings, there is a need for better apps written on better foundations (e.g. Python and Node.js). As an example, Mailpile (Python on the server) looks very promising in terms of Gmail-competitive usability aspirations. Unfortunately, as of December 2014, it’s not ready for use yet. (I tried and, yes, filed bugs.) Ethercalc and Etherpad (Node.js on the server) are other important apps.
With apps, the question doesn’t seem to be whether people know how to write them. The question seems to be how to fund the development of the apps so that the people who know how to write them can devote a lot of time to these projects. I, for one, hope that e.g. Mailpile’s user-funded development is sustainable, but it remains to be seen. (Yes, I donated.)
A crucial missing piece is having a system that can be trivially installed on suitable hardware (or, perhaps in the future, can be pre-installed on suitable hardware) that allows users who want to get started without exercising their freedom to modify the software but provides the freedom to install modified apps if the user so chooses and-perhaps most importantly-makes the networking part very easy.
There are a number of projects that try to aggregate self-hostable apps into a (supposedly at least) easy to install and manage system. However, it seems to me that they tend to be of the PHP flavor, which I think fundamentally disadvantages them in terms of becoming competitive with proprietary centralized Web apps. I think the most promising project in the space that deals with making the better (Python and Node.js-based among others) apps installable with ease is Sandstorm.io, which unfortunately, like Mailpile, doesn’t seem quite ready yet. (Also, in common with Mailpile: a key developer is an ex-Googler. Looks like people who’ve worked there know what it takes to compete with GApps…)
Looking at Sandstorm.io is instructive in terms of seeing what’s hard about putting it all together. On the server, Sandstorm.io runs each Web app in a Linux container that’s walled off from the other apps. All the requests go through a reverse proxy that also provides additional browser-site UI for switching between the apps. Instead of exposing the usual URL structure of each app, Sandstorm.io exposes “grain” URLs, which are unintelligible random-looking character sequences. This design isn’t without problems.
The first problem is that the apps you want to run like Mailpile, Etherpad and Ethercalc have been developed to be deployed on a vanilla Linux server by using application-specific manual steps that puts hosting these apps on a server out of the reach of normal users. (Mailpile is designed to be run on localhost by normal users, but that doesn’t make it reachable from multiple devices, which is what you want from a Web app.) This means that each app needs to be ported to Sandstorm.io. This in turn means that compared to going to upstream, you get stale software, because except for Ethercalc, the maintainer of the Sandstorm.io port isn’t the upstream developer of the app. In fairness, though, the software doesn’t seem to be as a stale as it would be if you installed a package from Debian Stable… Also, as the platform and the apps mature, it’s possible that various app developers start to publish for Sandstorm.io directly on one hand and with more mature apps it’s less necessary to have the latest version (except for security fixes).
Unlike in the case getting a Web app as a Debian package, the URL structure and, it appears, in some cases the storage structure is different in a Sandstorm.io port of an app and in a vanilla upstream version of the app. Therefore, even though avoiding lock-in is one of the things the user is supposed to be able to accomplish by using Sandstorm.io, it’s non-trivial to migrate between the Sandstorm.io version and a non-Sandstorm.io version of a given app. It particularly bothers me that Sandstorm.io completely hides the original URL structure of the app.
And that leads to the last issue of self-hosting with the ease of just plugging a box into home Ethernet: Web security and Web addressing are rather unfriendly to easy self-hosting.
First of all, there is the problem of getting basic incoming IPv4 connectivity to work. After all, you must be able to reach port 443 (https
) of your self-hosting box from all your devices-including reaching the box that’s on your wired home Internet connection from the mobile connection of your phone. Maybe your own router imposes a NAT between your server and the Internet and you’d need to set up port forwarding, which makes things significantly harder than just instructing people to plug stuff in. This might be partially alleviated by making the self-hosting box contain NAT functionality itself so that it could take the place of the NATting home router, but even then you might have to configure something like a cable modem to a bridging mode or, worse, you might be dealing with an ISP who doesn’t actually sell you neutral end-to-end Internet routing and blocks incoming traffic to port 443 (or detects incoming traffic to port 443 and complains to you about running a server even if it’s actually for your personal use so you aren’t violating any clause that prohibits you from using a home connection to offer a service to the public).
One way to solve this would be standardizing simple service were a service provider takes your credit card number and an ssh public key and gives you an IP address. The self-hosting system you run at home would then have a configuration interface that gives you an ssh public key and takes an IP address. The self-hosting box would then establish an ssh reverse tunnel to the IP address with 443 as the local target port and the service provided by the service provider would be sending port 443 of the IP address to this tunnel. You’d still own your data and your server and you’d terminate TLS on your server even though you’d rent an IP address from a data center.
(There are efforts to solve this by giving the user-hosted devices host names under the domain of a service that handles the naming, such as OPI giving the each user a hostname under the op-i.me
domain, but then the naming service—not the user—is presumptively the one eligible to get the necessary certificates signed, and delegating away the control of the crypto defeats an important aspect of self-hosting. As a side note, one of the reasons I migrated from hsivonen.iki.fi
to hsivonen.fi
was that even though I was able to get the board of IKI to submit iki.fi
to the Public Suffix List, CAs still seem to think that IKI, not me, is the party eligible for getting certificates signed for hsivonen.iki.fi
.)
But even if you solved IPv4-level reachability of the home server from the public Internet as a turn-key service, there are still more hurdles on the way of making this easy. Next, instead of the user having to use an IP address, the user should be able to use a memorable name. So you need to tell the user to go register a domain name, get DNS hosting and point an A record to the IP address. And then you need a certificate for the name you chose for the A record, which at the moment (before Let’s Encrypt is operational) is another thing that makes things too hard.
And that brings us back to Sandstorm.io obscuring the URLs. Correction 2015-01-24: Rather paradoxically, even though Sandstorm.io is really serious about isolating apps from each other on the server, Sandstorm.io gives up the browser-side isolation of the apps that you’d get with a typical deployment of the upstream apps. The only true way to have browser-enforced privilege separation of the client-side JavaScript parts of the apps is for different apps to have different Origins. An Origin is a triple of URL scheme, host name and port. For the apps not to be ridiculously insecure, the scheme has to be https
. This means that you either have to give each app a distinct port number or a distinct host name. On surface, it seems that it would be easy to mint port numbers, but users are not used to typing URLs with non-default port numbers and if you depend on port forwarding in a NATting home router or port forwarding through an ssh reverse tunnel, minting port numbers on-demand isn’t that convenient anymore.
So you really want a distinct host name for each app to have a distinct Origin for browser-enforced privilege separation of JavaScript on the client. But the idea was that you could install new apps easily. This means that you have to be able to generate a new working host name at the time of app installation. So unless you have a programmatic way to configure DNS on the fly and have certificates minted on the fly, neither of which you can currently realistically have for a home server, you need a wildcard in the DNS zone and you need a wildcard TLS certicate. Correction 2015-01-24: Sandstorm.io instead uses one hostname and obscure URLs, which is understandable. Despite being understandable, it is sad, since it loses both human-facing semantics of the URLs and browser-enforced privilege separation between the apps. To provide Origin-based privilege separation on the browser side, Sandstorm.io generates hostnames that do not look meaningful to the user and hides them in an iframe, but the URLs shown for the top-level origin in the URL bar contain equally obscure random-looking identifiers (even if an app could also supply a non-obscure part). I find it unfortunate that Sandstorm.io does not mint human-friendly URL bar origins with the app names when it is capable of minting origins. (Instead of https://etherpad.example.org/example-document-title
and https://ethercalc.example.org/example-spreadsheet-title
, you get https://example.org/grain/FcTdrgjttPbhAzzKSv6ESD
and https://example.org/grain/o96ouPLKQMEMZkFxNKf2Dr
.) Fortunately, Let’s Encrypt seems to be on track to solving the certificate side of this problem by making it easy to get a cert for a newly-minted hostname signed automatically. Even so, the DNS part needs to be made easy enough that it doesn’t remain a blocker for self-hosting a box that allows on-demand Web app installation with browser-side app privilege separation.
There are lots of subproblems to work on, but, fortunately, things don’t seem fundamentally impossible. Interestingly, the problem with software that resides on the phone may be the relatively easy part to solve. That is not to say that it is easy to solve, but once solved, it can scale to a lot of users without the users having to do special things to get started in the role of a user who does not exercise the freedom to modify the system. However, since users these days are not satisfied by merely device-resident software but want things to work across multiple devices, the server-side part is relevant and harder to scale. Somewhat paradoxically, the hardest thing to scale in a usable way seems like a triviality on surface: the addressing of the server-side part in a way that gives sovereignty to users.