[MUSIC]
All right, without further ado,
I would like to present LaForge,
who will be speaking today,
Demystifying eSIM Technology.
Please, take it away.
[APPLAUSE]
Okay.
Yeah, thanks.
So we can get started.
Demystifying eSIM Technology.
So, yeah, so, well, very quick slide about me.
I'm a recovering Linux kernel hacker.
I did a lot of work in the OsmoCom project.
It's open source mobile communications.
That's like the actual communications part,
not eSIM so much.
It's a completely different topic.
Yeah, participating at the CCC camps
and other events for quite some time.
I work mostly on implementing
various telecommunication protocols.
And in my spare time,
I also implement telecommunications protocols,
but going back to the like 70s and 80s and so on.
So historical telecommunications.
And as part of that, there's also an ISDN
and a PSTN network at the camp.
So if anyone wants to still connect to that,
come talk to us.
So after the advertisement break,
yeah, overview.
So what is this about?
Going to do a little bit of a recap
on classic SIM, USIM kind of stuff.
Then talk about principles behind eSIM,
the different variants of eSIMs,
and how all of this is put together.
Be warned, this is a rather complex topic.
Like probably almost anything in telecommunications.
And yeah, this is just a very brief glimpse
into what is happening technically.
I mean, this is like dozens and dozens
of specification documents and so on.
So yeah, let's look a bit at the classic SIM
to put this into context.
So SIM cards in the telecom networks,
as we know today, were introduced with GSM,
the 2G technology.
That means it was first deployed commercially in 1991.
The idea of the original SIM card is what we call
a single purpose smart card.
I mean, it's a smart card,
a card that's not just memory,
but has a processor and an operating system
and so on inside the card.
And it only has a single purpose,
which is to be used in the GSM network.
The fundamental purpose of that classic SIM card
is that you store network configuration data
on the card, so you can move the,
like have operator-specific configuration
that you move between the devices.
You have to move the card between devices.
Back then, also storage of contacts
and storage of SMS messages was an important feature.
And last but not least, maybe the most critical part
to serve as a secure element for the per subscriber
key material for authenticating the subscriber to the network.
These are the functions of the classic SIM card.
So then, you know, a decade later,
around 2000, UMTS 3G was introduced.
And in that, we went from SIM to USIM.
And this means also to UICC.
So now, U-SIM probably some people will have heard,
so it's the UMTS SIM, basically the 3G and beyond SIM card.
And they didn't just create another single purpose card,
but they also introduced an additional layer,
which is the UICC, the universal integrated chip card.
So it's a general purpose multi-application card,
where multiple applications can run on the card.
And the USIM is just one application on the card.
A classic SIM, in addition for backwards compatibility,
might be another application on that card.
And later on, when Volte came around for LTE,
there was also an additional ISIM application,
ISIM for IMS, subscriber identity module.
That's what SIM stands for.
So again, configuration data that's for the IMS core,
IMS being the IP multimedia system,
being the strange SIP derivative that is used in voice-over LTE
and voice-over Wi-Fi networks.
So by now, we really have thousands of parameters
and hundreds of files in configuration on that.
But still, fundamentally, it's the functionality of the secure element
to authenticate the subscriber to the network.
And with the USIM also to authenticate the network to the subscriber.
Whereas in the classic GSM SIM, we only had one-way authentication.
Now with the USIM, we have mutual authentication.
The same USIM is used in 3G, in 4G, and in 5G.
There's no change to the authentication, nothing of that sort.
So a 3G SIM card works for 5G or for 4G or for 3G,
or even for 2G if it has the backwards SIM application on it.
Now with eSIM, basically, we arrive at a point where
technology has been created to virtualize the entire USIM.
So not the classic SIM card, but the USIM.
And what that means, we decouple, let's say, like in software virtualization,
we decouple the operating system and the software from the underlying hardware.
We do the same in the eSIM universe.
And that happens by having a special chip, which is called the EUICC.
We had the EUICC as the classic card on which the USIM
and potentially the iSIM application was running on top,
but it was still a plastic card that you plug into a phone.
And now we have the EUICC, the Embedded Universal Integrated Chip card,
which is a chip that's fixed most often.
It can also be a card form factor, we'll get to that later,
but in a general sense it is a fixed chip inside the device.
Also there's work being done to actually not have it as a separate chip,
but have it inside a multi-chip package or even have it virtualized inside a chip,
but that doesn't really matter to the eSIM specification point of view.
So you have something that behaves like an EUICC chip as specified,
and that is the physical secure element.
And then we have something called SIM profiles.
And the SIM profile is basically a software or data description format
that contains what a classic USIM would contain,
what meaning it contains.
Please mute your phone if possible, thanks.
So we have the contents of the USIM file system.
I think it was a slide, I didn't speak about it explicitly,
but all the configuration data is stored in files on a file system in the card.
And all the content of those files, basically there's a description format in ASN1 encoded
where you can say, well, this file with this name has this content,
and there's another file with some other content, and so on.
So that's part of this eSIM profile description.
And then in addition we have the key material for the cellular network authentication,
meaning the K and OP or K and OPC values.
These are the shared secret key material that only exists at the cellular network operator
and inside the SIM, and here in this case in the SIM profile.
In addition to that we have further key material for over-the-air SIM card communication, that's OTA.
There have been many talks before at CCC events about how OTA works
and all kinds of security issues in at least previous OTA implementations and so on.
Feel free to refer to that if you're interested in that.
But that also is part of the SIM.
And that's not part of the file system, so it's listed separately.
Also you have all your PIN values, PIN2, PAC2, the admin PIN,
and also all the SIM toolkit applets, which are Java applets that the operator can run on your classic SIM or USIM.
And those are also part of the profile package that gets put together just to form the SIM profile.
And the eSIM profiles are specified, the format of those profiles is specified in what's called an EUICC profile package format
that is authored by the Trusted Connectivity Alliance, which formerly was the SIM Alliance.
That's a different standardization body than all of the other stuff that I'm going to talk about.
It's an interesting split of, well, some guys do some specification here and some other guys do specification over there.
So let's have a quick look at the EUICC.
I'm sorry for the low contrast in bright sunlight kind of rendering here.
Hopefully on the recording we have that then digital.
So this is taken from the specs, a schematic overview of the EUICC.
Not going to go through every acronym in here.
But basically we have a fundamental operating system at the bottom.
And then we have these two large, well, sort of rectangular objects here.
So-called MNO enabled profile and the MNO disabled profile.
So basically on this card that is symbolized by this diagram, we have two eSIM profiles residing on a single EUICC.
And one of the profiles is enabled and the other profile is disabled.
So you can have multiple or even many different profiles on an EUICC, but only one of those profiles is always active at any given point in time.
And you can switch between them.
Now each of those profiles contains a number of things.
We said already the file system, the access credentials, some certificate authority, security domain.
We have applets, we have policy rules and whatnot.
In general, the important part for also later slides and so on is that we have the issuer security domain of the provider, the ISDP here.
And we have outside of the profile the issuer security domain, the ISDR.
That's sort of the root of the EUICC.
So we have different security domains within the card operating system.
And every time you install an additional profile, there will be a new security domain and a new container that is isolated from all the other containers running on your EUICC.
And there's no way how, at least if everything behaves according to spec, of course,
these containers can escape their protection mechanisms and so on.
So why do we have this kind of complex setup?
The reason is, and it will get much more complex if you look at all the other parts of the system,
but the reason is in the end what we are talking about here is the core revenue generator for mobile operators.
They need to be able to securely identify their subscribers and they need to rely on the fact that SIM cards
or even virtual SIM cards in the form of SIM profiles cannot be cloned.
If they would, the business model would fall apart.
And now we have different operators who are competitors in the market who both install something on a shared chip.
So they all must trust that the security promises that this chip and the system and everything has
protects their vital shared secrets, the key material inside those containers or inside those profiles.
So that's why there's all this procedural security and certification approvals that we will get into shortly.
So what's the EUICC? Well, it's a smart card chip.
We have higher requirements in all kinds of ways on the security side, more crypto,
more guarantees of isolation between different things on the card,
various additional cryptographic routines compared to classic SIM cards,
and all the other bits are really the same. So the electrical interface is identical to a SIM card,
even though it might be physically packaged in a different package, but it's the same protocol, same transport protocol.
You can actually purchase also EUICCs in a plastic card form factor.
You can plug them into a device that doesn't have an EUICC built in or doesn't have an EUICC with the features that you want or something like that.
So this is really just a packaging aspect.
Each EUICC is identified by what's called an EID. That's the EUICC identifier, unsurprisingly.
So that's the unique identifier of the EUICC. That is different from the ICC ID,
which was the unique identifier of a traditional SIM card or used SIM card.
And since everything is virtualized, the ICC ID of a former physical SIM card now becomes part of the profile package.
So every profile has its own ICC ID, since it's a virtualized card.
So we need a new unique identifier for the actual physical card, which is the EID in this context.
So the other thing to always keep in mind when talking about eSIM stuff is that there are three different flavors of eSIMs.
There is the machine-to-machine eSIM, there is the consumer eSIM, and now there is, since this year, at least specification-wise,
I don't think anyone has it in the market yet, the so-called IoTs.
Now, of course, the first question that every nerd asks me, "Well, where's the difference between M2M and IoT?
Is IoT not just the new acronym for M2M?" Yeah.
They could just also have called them the red, blue, and the green card.
Those names are just some random marketing terms.
Just, you know, there's three different systems with different properties and different aspects and so on,
which we will look into now in the remainder of the talk.
Just keep in mind those are different, and they're not interchangeable, and they're not compatible with each other.
So this is different systems.
They share a lot of technology, but they're intentionally different.
So the first eSIM standard that was specified is the M2M model, the machine-to-machine SIM,
because that was apparently the driving force early on to have some kind of massive fleet of devices out there somewhere
that remotely the owner of those devices can provision new profiles and can switch between operators
without having to replace physical cards, which makes a lot of sense, of course, from the point of the owner of those devices.
So in the machine-to-machine model, the user interaction of the end device, the modem or the phone or whatever,
is not desired or even possible because either there may not be a human user in front of the device
or the device may not have a user interface at all.
So it's some, you know, whatever, you say card tracking device or some whatever machine-to-machine thing.
Now, it uses a server-driven push model to provision and manage profiles.
So the initiation of deploying new profiles on the card comes from the backend side, from the owner of those devices.
Basically, they decide they want to switch mobile operators and install a new eSIM profile into it.
So that's a push model coming from the backend side.
The actual download happens over what's called the BIP, the Bearer Independent Protocol,
which is something that exists also for, I think, well, 25 years or so.
It's a way how on-card entities, being Java applets or the SIM card itself or parts on the SIM card,
can communicate with something typically called the OTA platform or the over-the-air platform at an operator.
So it's a channel between some code on the SIM card and some code at the operator that is transparent
and where those two pieces of code can exchange data, whatever they want.
And this is also used in this context. All the management is remote.
And since all the management is remote, the EUICC must also contain a provisioning profile,
meaning an initial profile, SIM profile, that's on the EUICC so that it can log onto some random cellular network
to then discover, oh, another profile needs to be pushed to me.
Without that provisioning profile, you have a chicken-and-egg situation.
That's different from the consumer model and other models.
So the elements, I mean, yeah, this diagram is probably hard to read here on the projector.
We have a couple of network elements here. We have the EUICC in the device.
We have the EUM, that's the EUICC manufacturer, so the company that produces the EUICCs.
We have the CI, the certificate infrastructure. We have the SMSR, the secure router.
And we have the SMDP, the acronyms. We will get to that in actually two slides, I think.
So, yeah, the data preparation, my bad, sorry.
So the SMDP is sort of the heart of the backend infrastructure of all of the three eSIM flavors that exist out there.
So data preparation in this context basically means putting together this eSIM profile from various different data sources,
signing it properly, delivering it properly to the EUICC and so on.
So it's the preparing, storing and protecting those SIM profiles and downloading those into the EUICCs that are somewhere in the field.
We have an additional component, the SMSR, which only exists in the machine-to-machine eSIM sphere.
SR is for secure routing. It's a bit of a sort of, let's say, a one-to-one relationship between the EUICC and an SMSR.
So an SMSR is some backend software thing running somewhere at some operator in the cloud or wherever.
And the EUICC is the chip that's in the phone.
And when the EUICC gets produced, there is a key material that ties it to one specific SMSR on the backend side.
So those are owned by the same entity or at least initially.
And SMDPs, there can be many. There can be many providers that operate SMDPs and that have SIM profiles and there's like a market and competition and so on.
But the EUICC and the SMSR are tied together.
And that's sort of the representation of the EUICC somewhere on the backend side.
The association is created by the manufacturer.
According to the spec, it's possible to replace it and move to a different SMSR operator.
But somehow the business and the commercial side of the technology don't really enable that to the extent that the specification authors would have envisioned.
So you again have a lock-in situation, right?
Previously, you were locked into the cellular operator of the physical card you put into your remote IoT or M2M device.
And now you're locked to an SMSR operator without whom you cannot deploy new SIM profiles to your cards.
So you've given control basically from one entity that you have no control over to another entity that you have no control over.
So it doesn't really solve the problem of enabling the owner of a fleet of M2M devices to actually do whatever they want remotely on their devices and switch operators as they please.
So this is an overview slide of the larger process.
So we have the mobile network operator on the left hand side that provides a profile description, meaning all this contents of the file system and whatever or not, to the SMDP operator.
The DP again is the data preparation, the core.
So there's many SMDP operators. I think it's like 20 or 30 even.
There's a list of GSMA accredited as a competition in the market.
And then they create first what's called an un-personalized profile.
And then there's additional personalization data that's also something that exists in classic SIM cards.
The personalization data is then basically the per subscriber unique data, right?
There's data that's shared across all the subscribers like the configuration which roaming networks and what not.
That's the identical on all the cards or SIM profiles.
But then there is card individual data like your IMSE, MSISD and all these kinds of things, ICC ID.
And that then gets part of that in the personalization process.
And then you end up with a personalized profile.
And then that profile gets encrypted and signed.
And then you have a protected profile.
And the protected profile then is downloaded onto the EU ICC through the SMSR.
So the SMSR is the gatekeeper, the proxy, the representation of the EU ICC.
And you must go through the SMSR.
And again, the entity who controls the SMSR controls what you do with your EU ICCs.
So, okay, that's the machine to machine model.
Now, for most of you guys probably more exciting, the consumer model, what you actually have on your smart devices,
is different where we have a pull model.
And not a push model from some backend, but we have a pull model where the user does something on the user interface
in front of their devices.
And that triggers the process of then downloading and installing and activating a new profile on the device.
The profile download is actually specified to use TCP/IP, not just BIP.
BIP is just a stream of bytes.
It could be any protocol inside, but in the consumer it's actually TCP/IP that is used in this context.
It introduces another new element, the SMDS.
There's no SMSR.
The DS is the discovery service.
And also you have something called an LPA, the local profile assistant.
Now, the local profile assistant is a piece of code that typically runs on your smart phone,
which provides you with some user interface and which then talks to the eSIM backend universe
somewhere out there in some data center.
And on the other hand, it talks to your EU ICC inside the device.
So it's some software, some app that runs onto your device,
either as part of iOS or Android or whatever the flavor of operating system is that you're using.
Now, the diagram looks slightly different, as you can see here.
We have no SMSR, so the SMDP can talk directly to the LPA,
which is the local profile assistant in your device,
and that talks to the EU ICC, to the chip card or the physical chip, not a card necessarily, inside your device.
And you have all kinds of other interfaces and whatnot.
I'm not going into all the details here. That would go too far.
Now, the local profile assistant, I mentioned is software on your device.
Now, there's also an evolution of that code, and now that's like the LPA on the device is the LPAD,
the local profile assistant on a device.
Now, we also have an LPAE, the local profile assistant on the EU ICC.
So since the EU ICC itself is a smart card with an operating system and software and all kinds of things,
you can actually move the local profile assistant completely into the EU ICC,
and then you have an embedded local profile assistant,
and that is something you can use in a legacy device that does not have a local profile assistant on the device,
but it's inside the EU ICC.
So you can use a legacy device that's not eSIM enabled with an EU ICC that has an LPAE embedded in it.
That's sort of one of the use cases of that.
The standard case, though, is the LPAD in the consumer sphere.
So we have the SMDP+.
I noticed, well, you noticed too, I hope, in the M2M model we had the SMDP,
and now we have the SMDP+, because it does something more than the SMDP did in the machine-to-machine model.
So it's the enhanced data preparation.
It does basically all of the things that the SMDP did, all this profile, you know,
profile personalization, profile protection, and all that stuff,
but it also has some additional features in there.
Now, again, going through the steps of what the SMDP is doing, or the SMDP+ in this case,
we first generate the profile package, that's the UPP, the un-personalized package.
Then we have the PPP, the protected profile,
and then it gets bound, the binding, to one specific EU ICC,
so it gets cryptographically assigned to that single EU ICC.
We will get to the PKI infrastructure that's behind that in a second.
It stores that profile as well until it is delivered to the EU ICC.
It takes also care of the delivery into the EU ICC, and also some other bits,
which I skip in considering the timing issues in this talk.
So we also have the Discovery Service, and the Discovery Service is something like a,
I can say a notification delivery system, because as I said,
all of the things that I've been talking about are initiated by the user.
So the user does something on their smartphone, and it triggers something,
and it goes to talk to some backend.
But maybe the backend doesn't really have the data yet that it's asking for, or something like that.
So maybe the eSIM profile is not ready yet, due to overload or whatnot, or what kind of situations,
and in this case, the SMDP+ can basically register at the SMDS
that there is something pending, some operation, some, I want to notify these cards,
these EU ICCs, and the LPA in the device is then polling regularly the SMDS.
Well, do you have some kind of notifications for me, yes or no?
And if yes, then inside the notification, it will know which SMDP+ has some pending operation,
and then the LPA-D will go to that SMDP+ and grab whatever is there for this EU ICC.
So it's some kind of, yeah, you could think of a poor man's SMSC or something like that.
So we have the security domains. I touched that very briefly initially when we talked about the EU ICC.
So we have the security domain of the certificate infrastructure that's all behind this.
That's sort of the root security domain on the card, on the EU ICC.
Then we have the ISDR that represents the SMSR, the secure router, inside the EU ICC,
and we have the ISDP. That's then for each of the providers, for each of the mobile operators
of which you install the EU eSIM profile, each of those eSIM profiles has an issue
or security domain of the provider.
And there can be multiple such issues of security, multiple eSIM profiles, each of those has an ISDP,
and each of those could point to a different SMDP, so a different backend server
who has been creating these eSIM profiles for that card.
Now the actual delivery from the backend side to the card goes through several tunnels,
which is illustrated in this diagram.
Roughly, let's say there's an outer tunnel that utilizes the existing encrypted over-the-air protocols
that exist for classic SIM cards and eSIM cards, and the least common denominator
for transporting this over is actually SMS transport, believe it or not.
And then if devices have further capabilities, and for eSIM they should,
there's other protocols like CATTP or HTTPS in modern implementations,
and yeah, so that's sort of the outer transport channel.
And then inside there we have an additional encrypted transport channel that's based on SCP-03.
If anyone has ever done work with Java cards, they will know SCP-03 as the secure protocol
how external programs interface with Java applets and Java cards.
If HTTPS is used as the protocol to deliver, it's TLS version 1.2 with pre-shared keys
and using the algorithm specified there, so it's a fixed set of ciphers and a fixed TLS version.
Now any people doing stuff with TLS will be like, "Hmm, this is strange."
But think about, well, if you actually implement this inside the EU ICC,
you're talking a very small microcontroller with constrained resources,
so you maybe cannot do public key cryptography with X.509 and RSA and whatnot,
but you go to pre-shared key and sort of try your best given the constraints you are.
So this is a diagram of the certificate change and the security relationships between the different elements.
I'm not going to walk through the diagram, which is probably impossible to read anyway.
So basically there is one route of trust operated by the GSMA,
the GSMA being the members club of the public operators of cell phone networks,
and they have a root certificate, or somebody has that on their behalf,
and this certificate is used to sign all the different elements in this universe.
So the root certificate is used to sign certificates for the EU ICC manufacturers,
so they can sign per EU ICC certificates on each EU ICC,
and then also the root certificate of the GSMA is used to sign certificates of approved SMDP pluses and SMDSs and all these network elements.
So all of them have to have certificates derived from the same single route of trust operated by the GSMA,
and in order to get access to that I think I have some slides, compliance security, exactly.
So the EU ICCs, there's a common protection profile on EAL 4 plus that needs to be certified for the EU ICC,
then you have certifications for the production environment, the process security,
so there is different, yeah, the SAS UP for the EU ICC personalization that's on the EU ICC side,
there is the SAS SM for the subscription management platform, so all the backend infrastructure,
the software must be certified, the hosting must be certified, the business processes must be certified,
and of course, I mean, I don't know, but I guess it costs a shitload of money to have any of these things certified,
I mean, given the complexity of these systems.
Interestingly, AWS now has a GSMA accredited hosting or cloud product,
so basically if you have a GSMA certified software, you can now run it in a GSMA certified cloud environment by AWS if you want that.
So in this case, you can afford not to have your data center certified, but you know, Amazon is doing that for you.
Yeah, then also there's functional compliance testing, so all of these software elements actually need to be tested
and also certified again by GSMA approved scheme that they have delegated to some entities that do this certification,
and then of course, all these manufacturers and so on all need to be accredited, and it's all enforced via this PKI.
Basically, if you do not comply with any of those rules, you do not get a certificate or your certificate gets revoked or something like that,
and then you cannot participate in this club anymore.
And of course, you need to be a GSMA member as far as I know as well in addition to all of that.
So, okay, a lot of talk about a lot of things.
Now let's look a bit at the procedures.
So we now know there are different elements.
There's sort of these SM things in the backend, and we have the EUICC in the device and the local profile assistant in the device,
and now each of these, they talk to each other, and there's a couple of different things that they talk to each other.
The first group of things is remote provisioning, meaning operations called profile download initiation,
which is a common mutual authentication profile download installation, sort of self-explanatory,
and then there are so-called local profile management operations about enabling and disabling a profile, listing the profiles on an EUICC.
You can even set nicknames, you know, can give them cute names, your profiles on the card,
and there is local EUICC management such as reading the EID from the device,
because if the local profile assistant, the LPA, wants to talk to the backend, of course it needs to tell the backend which EUICC is actually making the request,
as memory, that stuff, and so on and so on.
So let's look at a couple of common operations.
So this is the first step. If you as a consumer are getting an eSIM,
that's the first step that's happening, is something called the download initiation,
and it starts by some kind of contractual relationship between you and the mobile network operator that is issuing this eSIM to you.
That means billing information, whatever is exchanged,
and then the operator goes through a backend interface, so the so-called ES2+ interface,
and talks to the SMDP+ operator, which most often is a separate company that's providing it as a service, it's not your mobile operator.
And the SMDP+ then does some stuff, generates additional identifiers, and so on,
and it generates, most importantly also, the code that you will use to actually then install the activation code,
or the most often displayed as a QR code, but actually it's just a string that contains the domain name of the SMDP+ plus some token
that sort of identifies which eSIM profile we're talking about here in this operation.
So that's a pure, it starts with a business operation between you and the mobile network operator,
it continues with some backend operation to the SMDP+ provider,
and nothing has actually happened by the end of the concluding that other than you being billed.
Now the next step is the download installation phase, and that's, I know it's small and so on,
but it's really just a very high level overview of what's happening there.
We have elements, we have the operator that's the mobile network operator that's selling you a SIM subscription,
we have the SMDP+ operator, the guy who operates the eSIM backend,
we have the LPAD, that's again your local profile assistant and the device, and we have the EUICC.
And now there's some talking going on, so the LPAD needs to query the EUICC,
like what is your EID and what's the default SMDP+ address, and so on and so on.
And then there is one line here called just, well, refer to common mutual authentication procedures,
actions, such and such, and that expands into a diagram that's like three times the size of this,
which does the mutual authentication between the EUICC and the SMDP+.
So at the end of this mutual authentication process, by facilitating all these PKI X509 certificates in this entire chain,
the EUICC knows it's talking to a GSMA accredited and approved SMDP+,
and the SMDP+ knows it is talking to an EUICC that contains a profile that has been issued by an EUICC manufacturer
who has received a certificate from the GSMI public key infrastructure.
So basically they both know they can trust each other because they're part of the same chain of trust.
And from that point onward then, the actual profile building and so on gets started.
It goes on for some time, and then we come to a process called the profile installation,
where the LPAD and the EUICC exchange a number of commands, so-called APDUs, that's smart card packets,
basically communication packets that go back and forth.
And when all of this has happened, at some point we come to a profile that has been successfully installed on the EUICC.
Now, a newly installed profile is by definition explicitly not activated.
It's downloaded and installed, but it's not active.
The act of activation is something you have to do explicitly by using a local profile management operation
between your LPAD on your device and the EUICC.
And the next step is the enabled profile device, where really it's only the end user using the LUI,
the local user interface, doing some end user interactions, the thing that end users do.
And then we have the EUICC and the device baseband.
Now, where does the device baseband come into this?
If you switch your SIM profile, the baseband processor that handles all the cellular protocol stuff with the network,
it needs to invalidate all the information it may have ever read from the SIM before,
including the IMZ and everything else, because your SIM has completely changed now.
It basically needs to invalidate all that, and that happens by a so-called refresh command.
So during this process it's basically determined whether refresh is needed.
In most cases, yes.
And if a refresh is needed, the EUICC, using something called proactive SIM,
which inverts the direction of the SIM communication,
because a SIM card can normally not initiate communication to the baseband.
It's only the other way around.
So there's a piggyback mechanism, how it can tell basically the baseband,
hey, by the way, all the information you think you knew about the SIM card is now invalid.
You need to basically start from scratch.
And it comes, restarts, and starts to read all the information from the SIM card,
and it determines it now is a new IMZ, and it needs to roam to a different network,
and it does the network registration, and so on and so on.
So that's what's happening once you enable a new profile in the card.
Now, that is the consumer model.
Now let's get to the exciting new buzzword, the IoT model.
Now, machine-to-machine consumers and now IoT.
Now, the IoT model has been developed mostly to overcome problems
in the machine-to-machine eSIM model,
where I already hinted this, there's the problem of sort of the business side
and the legal side not really being able, the commercial side not being able to agree
on transferring sort of the SMSR from one SMSR operator to another
in the machine-to-machine case.
And now they created something which I think is actually really nice.
I'm rather happy with how it worked out.
So we take a lot from the consumer eSIM.
So the IoT eSIM has much more in common with the consumer eSIM
than with the machine-to-machine eSIM, which is sort of paradoxical if you think about it,
but it is the way, this is the way.
And it's sort of like a consumer eSIM that's remote controlled.
So instead of having this completely separate scheme with the SMSR
and whatever kind of operations and the push model,
what we do is we use the consumer model,
but instead of a local user entering an activation code,
we sort of have a remote user that injects the activation code
so it can do the thing to activate a new eSIM profile.
And that's nice in a way that we do away with this dependency on one entity
that has the control over this EU ICC,
and we get to the whatever, 30 or so entities that compete
which is slightly better than one entity.
And the way how they do it is they take the LPA,
so the local profile assistant that's running in your smartphone,
and they split that in half.
And the upper half of the LPA becomes the EIM, the EU ICC Identity Manager,
which is yet another piece of server software running somewhere in a data center.
And the lower part of it becomes the IPA.
It's not a beer unfortunately, it's the IoT profile assistant I think.
And the IPA is sort of a user interface less LPA
introducing an interface to the EIM, which is the server side infrastructure,
which then does the same thing as the user would have done,
such as sending an activation code to install a new eSIM profile in there.
So the goal I set was to work around these problems with SMSR migration and machine to machine.
So it turns out that IoT devices occasionally tend to be even smaller
in terms of CPU resources on their application processor
than the machine to machine devices in the past.
So it might be overkill to require that they actually implement a full blown HTTP and TLS stack
that might be difficult in some environments.
What they did is they worked this new interface between the IPA and the EIM,
the eSIM IoT Remote Manager, called ESIPA, that interface.
They designed this in a way that it can be spoken over.
First of all, there's two different encodings.
There's JSON encoding for high powered devices that can handle textual representation,
there's an ASN1 representation for low powered devices that need binary encoding formats,
and each of those encodings can be transported either over HTTPS or over CoAP,
which is an IoT related protocol for resource constrained devices with Datagram TLS,
which is simpler than the TCP based TLS as we know it in HTTPS.
You can even implement a completely custom transport if you want to,
because as an owner of a fleet of I don't know how many IoT devices out there,
you can of course put some code as IPA on your device and some other code as EIM in your backend
and they can talk about whatever protocol they want,
just as long as they can encapsulate all the operations and whatever that is needed.
Of course you won't be able to interoperate with other devices,
but technically it's possible in the spec even explicitly says,
"Yeah, if that's what you want to do, you can do it."
So, yeah, it can be remotely triggered.
So basically the customer of such an IoT subscription,
so you buy 100,000 IoT eSIM profiles and as a customer you would operate your own EIM
or you would contract some party, a third party that is neither your operator nor the EUICC manufacturer,
a third party that really just works for you to operate that EIM or your operator in-house.
And through this EIM you can remotely install whatever profiles you want on your IoT fleet of devices
and nobody else can basically tell you not to do that other than the GSMA,
but that's not their role.
So, yeah, that's sort of what's new in the IoT model.
Now, last part, just a couple of slides about eSIMs versus private networks,
which is a topic that's also relevant to here at the CCC because this private seller network operated here.
Now, the entire GSMA eSIM universe has been built around a couple of assumptions,
which I think were even wrong back then and they were even wrong right now.
So, well, a central root of trust, okay, I mean, if you're a GSMA, of course that's what you want, right?
I mean, you want to be the root of trust, that's sort of understandable.
GSMA members or accredited parties issuing profiles, okay, I can still understand that,
but then there is, for example, the requirement that you need public Internet access
to reach all of these SMDP, SMSR, SMDS devices, which, yeah, well, I have this private network of whatever.
I don't want those devices to talk to the public Internet,
but in order to install new eSIM profile, they now need Internet access.
Yeah, not the smartest idea.
And then also the OTA mechanisms, they all require an initial trigger of SMS.
So, in your private network where maybe you have data-only devices and you have no use for SMS or voice calls
and you would now have no technical reason to deploy that technology,
you now need to deploy an SMS service center just so you can trigger the HTTPS connection activation,
so you can download eSIM profiles over public Internet access from devices that you never wanted to have public Internet access before.
So, yeah, well, so in private networks, you know, and I'm talking about, you know, the event networks like here,
or also campus networks, let's say, at a car manufacturer or whatnot, that's not really what they want in the end.
Yeah, thanks. I'm coming to the end here.
Yeah, so, yeah, you might not be a GSMA member, your network might not be public,
you might not want public Internet access, and you might not want to have to deal with legacy SMS.
So, yeah, there is sort of a disconnect between what's happening in, you know, the cellular world and in the eSIM world to some extent.
Now, what you can do is basically give two options.
Either you are part of this GSMA world, and that means you have to comply with all those requirements and so on,
and your profiles are over the public Internet, and actually you're working in a system that's meant for public networks,
but actually you do use them in a private network because you have no other way,
or you theoretically, I don't think anyone does that, at least not yet, you would operate your alternative own route of trust,
like CA cert was created to sort of as an alternative to commercial CA's,
where then you would run your own SMTPs, SMSRs, and all that infrastructure.
The problem is then you cannot work with a normal consumer device because the EUICC in there has a certificate from the route of trust of GSMA,
and that would of course not accept any of the certificates of your own CA.
So that can only work in a situation where you produce your own devices and put EUICCs on those devices,
or like in a plastic form factory in a SIM slot that have certificates derived from your own PKI in there, right?
So that's sort of, yeah, both choices are rather bad.
So here at the camp the solution is obviously go for the first part because people come here with normal consumer devices,
so this time is the first time that the GSM team has some eSIMs available, if you ask them,
this is a limited supply because it's of course much easier to buy physical SIM cards than to buy a blob of data,
it's of course in much more limited supply than physical cards.
And the problem is, well, of course you have to do this through some service provider,
and it's all done by the service provider, you can't run off all of that, you can't run it on premises,
you can't control what's happening, it's basically all out of your hands, and that's sort of the negative part of it.
And it also means that this service provider then knows of course the EID of all the people who have joined this camp here,
and if you buy a physical card here nobody knows except maybe some of the people here,
but at least nobody off site and not some company somewhere.
So, yeah, I forgot, one more slide.
So me being an open source guy, what can we do with open source in this universe?
And the answer is, well, technically everything, but then how do we get all of this accredited and approved and whatnot,
and authorized so it can be used in production environments?
So all of the specs are public, you can implement all of that, but you can't really use it with consumer devices
because your software won't get the GSMA approval, and your hosting at home won't get GSMA approval,
and so yeah, sort of stuck there.
Now in the IoT eSIM, luckily there are two components which do not require GSMA certification,
which is the IPA, the local software running on the device, and also the EIM, the EICC identity manager,
which is the part that you as an operator of a fleet of IoT devices want under your control.
So there's some chance of at least having free and open source implementations there.
And for the LPA or IPA, Google actually released the one that's used in Chrome OS as open source software,
so if anyone wants to look at how this is done, you can do that and port that to a general,
you can buy an EICC in a normal form factor, plug that into your laptop,
and then try to run that local profile assistance from Chrome OS to get a feel of what's happening there,
what does the protocol messages look like, and so on. That's actually possible.
Okay, and with that we come to further reading and the end of file,
and we hopefully still have a few minutes for questions and hopefully some answers as well.
Please raise your hand as a signal angel, and yeah, thanks.
[Applause]
Yeah, so we...
So we have decided to extend Q&A if there are questions.
We are extending Q&A, so hopefully there will be enough time for questions.
Yeah, please line up here with the gentleman in the shirt over here, the violet shirt.
Yeah, blue shirt.
Yeah, thank you for the talk.
So I have a question. So I have a phone that can do eSIM, and it has two SIM slots,
so I can install ten SIM cards to my phone, but I can only activate two of them, so in whatever combination.
What is the reason for this?
Well, that is a general issue with cellular networks and how they work in a sense that
the entire spec and everything is designed in a way that there's one subscriber using one modem being attached to one network,
and if you think of it physically, how it works, different operators get different spectrum,
and your modem needs to tune to one particular frequency, right, and it can only be at any given point in time on that one frequency.
Now, if you have a dual SIM phone, that usually means you have also a dual baseband phone, at least these days,
which means you basically have two complete cellular modems in there,
and they can be on two channels of two operators or two technologies and so on.
Thank you for talk. One thing I didn't get is you've succeeded in doing eSIM here,
which means that you got through a lot of hoops, but what is the limiting factor for the eSIMs in the camp?
No, I mean, first of all, I had no involvement with the eSIM here at the camp, just to be clear.
As in the GSM team, I don't know what they did and whom they talked to and whatnot,
but I guess it's basically those limited number, I think it's about 350 or something like that,
they got for free from some company and that's the quantity they got for free.
I guess that's sort of the...
They rely on the company that's generated...
Yes, of course. There's no other way you can do it with a general consumer device that has the GSM able to trust that you can't do anything else.
Hello, if I were to route my phone and have control of the operating system, would that solve the problem with the certificate?
No, it does not, because all of this happens inside the EU ICC itself.
So there is no reason... like you can do whatever you want on the phone, on the baseband, you can route it, you can do whatever you want,
but in the end, let's say the secure connection is always between...
encrypted connection is always between some code inside your SIM card and some code somewhere in the cloud.
So the goal here obviously is to just get some numbers over the year into your EU ICC.
In your professional opinion, if I may say so, was there any way that the protocol suit could have been made simpler without compromising usability or security?
Yeah, I don't really know, to be honest.
It's not really my... I've never designed any of these systems.
I just look at them and think about them and work with them.
So yeah, I don't really know.
As usual, when you have some kind of specification group, there's different people with different interests.
Some of them, well, a very small amount of them being technically, and all the other interests are commercial, and then they clash,
and then everybody wants to get their pattern in the standard and whatnot, and then you end up with something horribly complex, you know, designed by a committee.
Thanks for the talk.
If I wanted to have my own commercial device, like a consumer device, and connect it to my own network,
and I wanted to put an eSIM on there, what hoops... So I understand that I would need to have that signed by the GSMA.
What hoops would I have to jump through to get that done, assuming that I want to have my own set of parameters that I put in the unpersonalized profile and the personalized profile?
Well, basically you need to find an SMDP+ operator with whom you enter in a commercial arrangement,
so you can give the profile data to them and they would create the protected profile for you assigned in this chain of trust and so on.
Yeah, and I don't know the commercial terms and so on.
If you want a list of those companies, there's a GSMA website that lists all of these accredited SMDP+ operators.
Yeah, but I guess, you know, mostly they would be interested, like, if you want tens of thousands or hundreds of thousands, but not fewer than that.
So that's sort of a bit of a problem there.
Hey, thank you for the great talk.
On the M2M eSIM model, what would happen if the SMSR provider were to go bankrupt?
It's probably a question of the escrow language in your commercial contract with that provider.
I don't know whether there's any... I'm not... like, that's more, I say, a business process kind of thing.
It's not really... I'm looking at the technical specs here.
It might be that they have foreseen this and there is some kind of part of the eSIM specs that cover those business aspects,
but I'm not aware of, like, any requirement there.
Hi, thanks for the talk.
I think early on you mentioned the possibility of virtualizing the EU ICC within the general processor.
Does this perhaps hint at the possibility of an EU ICC where multiple EU ICCs could be run perhaps with different routes of trust?
Yes, potentially.
Though it would mean that, of course, you would have to be able to execute code in the context of wherever this EU ICC,
if you want to call it like that. I think it's called an EU ICC then or something like that.
I think I've heard that term in the industry.
Yeah, you would have to execute it with that level of trust and I'm not sure in which kind of secure enclave Voodoo in those processes they're trying to do that.
So, also doesn't look like a very easy path.
So, speaking of secure enclaves, if I understand correctly, any profile could be installed in any EU ICC,
which means that there is a single key extraction standing between us and accessing all the secrets of all the possible EU ICC devices.
So, if we manage to extract one set of secrets, then we can create a fake EU ICC that would pass attestation?
No, I mean that would be the case if it was a shared secret symmetric cryptography thing.
But there's actually a public key. It depends on which specific interface and so on, but in the end,
if you get in any kind of PKI, if you get to the private key of the root CA, then the system is owned.
But, of course, in any PKI you try to make that as hard as possible.
If you just break the key of one particular device, you never would be that device, but not the overall system, right?
Yes, but I could install another eSIM profile in that same device and extract the keys from that eSIM profile too.
No, you would not, because in order to install an eSIM profile on an EU ICC, you need a certificate of an SMDP+.
And not a certificate of an EU ICC, right?
So, it's a different tree in the PKI hierarchy and all the code in place.
Of course, it makes sure that you cannot use a certificate of an EU ICC and impersonate an SMDP+ or something like that.
Okay, maybe next question. Yeah, thanks. We still have time? Okay.
Following the idea of PKI hierarchies, I mean, there are a lot of issuing CA's, however, they are probably called involved in here.
And this would require revocations. Are they being properly done? Are there such revocation events already happened?
And did they arrive at all devices? Can you say anything about that?
I did not look into that, sorry. I wish I knew. But yeah, sorry, didn't look at that.
In the IoT spec, how do we do the communication between the EIM and the IPA if we don't already have a different profile?
Is there like some facility or do we have to flash some initial network contract?
You can, well, I think there's different ways how you can do that.
Well, first of all, the device could have some other network technology by which you could reach, and there could be anything, right?
So assuming you're designing an IoT device and you can at least run some custom software on that IoT device,
you can implement whatever protocol you want to talk to whatever part of software you have somewhere else over whatever medium.
And then that software basically is a part of your EIM that talks over the public Internet to the SMDP+ and to all of that.
So because that is not possibly technically with the earlier E-SIM profiles, but because the way how the IoT was designed,
basically you are enabled to be a proxy in there, and the proxy can of course have multiple parties and tunnel over whatever protocol.
And it could also be that this other medium is a couple of test points in the factory while you're producing the device.
That's also a medium by which you could facilitate that transfer.
Okay.
All right, I believe that's all of the questions. Once again, thank you LaForge.
Yeah, thanks.
[Music]