Explain E-Sim Cards to Me like I am 5
July 2, 2023 1:06 AM Subscribe
I asked a question about how to get data roaming for a trip and one suggestion was an Esim card. The price looks right, but i can't figure out what these ARE, or how they work or if they work with my Samsung Galaxy S22+. Can someone please explain. As before this would be in Eastern Canada. More specific confusion inside.
Here are some of the many things I do not know:
1. Can I use this with my phone? It's a Samsung Galaxy S22+. Google suggests the answer is yes, but I find the answers to this question hard to understand because I don't know so many other things..like...
2. Is this a physical sim card? Or is a number or code or account I enter somewhere in my phone?
3. They are data only, it seems. Does that mean I can keep my existing SIM card and phone number in there and thus use my existing accounts/phone etc. etc. and still make and receive phone calls on my existing number at the same time?
4. Are there security concerns here? Like what network is the data stream using and can this somehow compromise my data/accounts/phone etc.?
5. More generally, how trustworthy are these things. Like if it says XGB at Yspeed can I assume I will get that or are they glitchy and sometimes just don't work? How can I know/check where I will get coverage?
6. [how much] Do i care about network type. 5G, LTE, etc. etc. I mean I used the internet before these existed and was fine, right? But I also used dial-up once and wouldn't want to go back to that with today's websites, so who knows.
Here are some of the many things I do not know:
1. Can I use this with my phone? It's a Samsung Galaxy S22+. Google suggests the answer is yes, but I find the answers to this question hard to understand because I don't know so many other things..like...
2. Is this a physical sim card? Or is a number or code or account I enter somewhere in my phone?
3. They are data only, it seems. Does that mean I can keep my existing SIM card and phone number in there and thus use my existing accounts/phone etc. etc. and still make and receive phone calls on my existing number at the same time?
4. Are there security concerns here? Like what network is the data stream using and can this somehow compromise my data/accounts/phone etc.?
5. More generally, how trustworthy are these things. Like if it says XGB at Yspeed can I assume I will get that or are they glitchy and sometimes just don't work? How can I know/check where I will get coverage?
6. [how much] Do i care about network type. 5G, LTE, etc. etc. I mean I used the internet before these existed and was fine, right? But I also used dial-up once and wouldn't want to go back to that with today's websites, so who knows.
I am currently using an eSIM for the first time, and I think I can answer your questions:
1) Having briefly looked at the manual for the S22, I am confident that you can use an eSIM
2) No, it is not a physical card. You will get a code or a QR code or something like that from the eSIM provider.
3) Yes, you can keep your existing SIM card and use it for calls and SMS but they will be billed at whatever your international roaming rate is. You can also turn off calls, etc., except when you think you need it (this will be a setting on your phone - I don't know exactly what it looks like on Android).
4) I don't think there are any security concerns beyond just the normal security concerns of using a cell phone and shopping online.
5) I've been happy with my $7.99 for 5GB/month Austrian eSIM so far. I've had some issues with getting a new network to "pick up" when crossing borders etc. but restarting the phone has fixed it so far.
6) I sometimes have 3G speed in rural areas (even with my "home" SIM) and it sucks. But LTE or 5G are generally fine for modern purposes.
posted by mskyle at 1:42 AM on July 2, 2023
1) Having briefly looked at the manual for the S22, I am confident that you can use an eSIM
2) No, it is not a physical card. You will get a code or a QR code or something like that from the eSIM provider.
3) Yes, you can keep your existing SIM card and use it for calls and SMS but they will be billed at whatever your international roaming rate is. You can also turn off calls, etc., except when you think you need it (this will be a setting on your phone - I don't know exactly what it looks like on Android).
4) I don't think there are any security concerns beyond just the normal security concerns of using a cell phone and shopping online.
5) I've been happy with my $7.99 for 5GB/month Austrian eSIM so far. I've had some issues with getting a new network to "pick up" when crossing borders etc. but restarting the phone has fixed it so far.
6) I sometimes have 3G speed in rural areas (even with my "home" SIM) and it sucks. But LTE or 5G are generally fine for modern purposes.
posted by mskyle at 1:42 AM on July 2, 2023
I have the Galaxy S21, which is compatiable, so there is no doubt your S22 will be. Before my last trip to the States in Oct 2022 I looked into getting a £26 eSIM, but as my carrier only charged £2 a day for data roaming, it was easier to do that for the 14-day trip, as I could still get texts, which I needed a couple of times for two-factor authentication codes to be sent by AmEx.
One of the major eSIM providers, Airalo, has a massive FAQ section which should answer all the questions you have about setting up and using eSIMs, particularly in relation to getting texts and calls.
If you want to use your usual number for calls, etc. you can, but I think you will need to switch between the eSIM and your physical SIM (it's a toggle setting), and then remember to switch back again to the eSIM, otherwise you'll continue to be charged roaming rates by your carrier, and depending on their T&Cs, this might be a daily rate, even if you switch back to them to get a single text or to make just one call.
posted by essexjan at 3:46 AM on July 2, 2023
One of the major eSIM providers, Airalo, has a massive FAQ section which should answer all the questions you have about setting up and using eSIMs, particularly in relation to getting texts and calls.
If you want to use your usual number for calls, etc. you can, but I think you will need to switch between the eSIM and your physical SIM (it's a toggle setting), and then remember to switch back again to the eSIM, otherwise you'll continue to be charged roaming rates by your carrier, and depending on their T&Cs, this might be a daily rate, even if you switch back to them to get a single text or to make just one call.
posted by essexjan at 3:46 AM on July 2, 2023
I meant to add, my carrier (Sky Mobile, UK) allowed me to receive UK calls and texts with no charge, but for my friends in the USA who I was visiting, I needed to use WhatsApp (which I'd generally use to call them anyway from home).
posted by essexjan at 4:02 AM on July 2, 2023
posted by essexjan at 4:02 AM on July 2, 2023
1) We can't answer this — it depends on whether or not you have a dual SIM model of the S22+ (which partially depends on the country where you bought the phone and the service provider you bought it from (if any).
2) It's not a physical card — often it's a QR code and often it's activated through an app that you download from a service provider.
3) They can be data only or they can behave the same way a physical SIM would behave and allow calls/SMS/etc. too — it all depends on what the service you choose is offering.
4) No security risks inherent to eSIM that I'm aware of — in theory, a hacker could download an eSIM to your phone but this hasn't been shown to be an actual threat that I've heard about.
5) I've experienced no difficulties with eSIM (on an iPhone) and haven't had a physical SIM for a few years now.
6) Think of it as the same as a physical SIM — it all depends on the service you select. 4G LTE is good for the vast majority of purposes for most people.
Near the bottom of this page it describes how to access the SIM card manager settings in your Settings app and customize the way your phone behaves in dual SIM mode (when you have a physical SIM and an eSIM at the same time). You can decide which SIM to use for calls, which one for data, etc.
posted by theory at 7:09 AM on July 2, 2023
2) It's not a physical card — often it's a QR code and often it's activated through an app that you download from a service provider.
3) They can be data only or they can behave the same way a physical SIM would behave and allow calls/SMS/etc. too — it all depends on what the service you choose is offering.
4) No security risks inherent to eSIM that I'm aware of — in theory, a hacker could download an eSIM to your phone but this hasn't been shown to be an actual threat that I've heard about.
5) I've experienced no difficulties with eSIM (on an iPhone) and haven't had a physical SIM for a few years now.
6) Think of it as the same as a physical SIM — it all depends on the service you select. 4G LTE is good for the vast majority of purposes for most people.
Near the bottom of this page it describes how to access the SIM card manager settings in your Settings app and customize the way your phone behaves in dual SIM mode (when you have a physical SIM and an eSIM at the same time). You can decide which SIM to use for calls, which one for data, etc.
posted by theory at 7:09 AM on July 2, 2023
An eSIM is purely the digital version of a physical SIM. Physical sims carry a little bit of data that describes who your carrier is and how to get hold of it. An eSIM is the data without a physical package. Something on your phone (with iPhones, it's usually an app, wouldn't be that surprised if android is similar) pulls that data from the provider's website and installs it into your phone's system in the hole where it's supposed to go.
Dual sims (can be one physical and one not or two non-physical) are supported by many modern phones. You can se your preferences about which one is used and which isn't, like all data over sim 2, outgoing calls over sim 2, that sort of thing. Typically (unless you turn one entirely off) you will receive incoming calls and texts on both of them and it will somehow tell you which sim is in use. Useful if voice roaming is good with your provider but data roaming is bad, for instance. Whichever sim you call through will be your outgoing number, so if you're using your new sim no one will recognise the number you're calling from when you're using mobile calls; over the internet you're not identified by your mobile phone number so nothing should change for WhatsApp and other stuff (WhatsApp knows your number because of the confirmation texts you did aeons ago when you set it up, not because of the device you're using).
There shouldn't be any security concerns. You'll be getting the sim from a mobile service company, so the sim data should be legit if the company is reputable (and I've never come across one that isn't). Quite honestly your phone does not trust the internet all that much and is sceptical, if you like, of the data it receives over sim 1; sim 2 will get the same treatment.
posted by How much is that froggie in the window at 11:56 AM on July 2, 2023
Dual sims (can be one physical and one not or two non-physical) are supported by many modern phones. You can se your preferences about which one is used and which isn't, like all data over sim 2, outgoing calls over sim 2, that sort of thing. Typically (unless you turn one entirely off) you will receive incoming calls and texts on both of them and it will somehow tell you which sim is in use. Useful if voice roaming is good with your provider but data roaming is bad, for instance. Whichever sim you call through will be your outgoing number, so if you're using your new sim no one will recognise the number you're calling from when you're using mobile calls; over the internet you're not identified by your mobile phone number so nothing should change for WhatsApp and other stuff (WhatsApp knows your number because of the confirmation texts you did aeons ago when you set it up, not because of the device you're using).
There shouldn't be any security concerns. You'll be getting the sim from a mobile service company, so the sim data should be legit if the company is reputable (and I've never come across one that isn't). Quite honestly your phone does not trust the internet all that much and is sceptical, if you like, of the data it receives over sim 1; sim 2 will get the same treatment.
posted by How much is that froggie in the window at 11:56 AM on July 2, 2023
Just to add to the great advice above: I’ve used eSIM cards many times for many trips and it was quite easy to adjust after initial panics. I don’t have regular calls but I do have WhatsApp and that works for me. If I top up on data, sometimes I have to fiddle with my settings. If you’re beer WiFi when it happens, it should be fine but even if not, it’ll work out. If you plan to use your phone for GoogleMaps and the like, definitely get a big data package. My phone has been a lifeline for me on this current trip! Yes you can save money but adding more later but running out unexpectedly can be a big pain especially if you are worried about being stranded.
posted by smorgasbord at 2:57 PM on July 2, 2023
posted by smorgasbord at 2:57 PM on July 2, 2023
So I believe the Galaxy S22 supports eSIMs, but it's a bit dependent on the ROM on the phone. If you bought an unlocked on direct from Samsung, you are almost certainly good to go — however, if you have a US phone that was bought via a carrier you are probably eSIM-capable but there's a chance it might be broken by the carrier locking and other 'customizations'. (Friends don't let friends buy carrier-locked phones!) That's really the only thing I can think of that might be an issue.
As to how eSIMs work... it's complicated. Basically, you are downloading an encrypted program which your phone sends to a tiny "secure" embedded processor (essentially the same as what's in a physical SIM card, properly called a UICC) soldered to your phone's circuit board. That program, when executed, will let your phone identify itself using a particular IMSI (SIM number), and will also perform handshakes against a secret key value which it is programmed never to reveal.
There's a bunch of complexity around the crypto used to obscure the details of the eSIM code package in transit... the whole point of which is to verify that the "eSIM" was issued by someone who was authorized by someone, who was authorized by someone, etc. etc., ultimately rolling up to the 3GPP Consortium, an industry group that "owns" the 4G / LTE (and most 5G) standards. And also that the package can only be decrypted, and the IMSI information accessed, inside of a compliant UICC chip.
The upshot of all this is that it's significantly harder (although not impossible) to get an eSIM without some sort of Internet access. You can't buy an eSIM from a disinterested market-stall vendor as easily as you can a traditional "hard" SIM. Provisioning an eSIM usually involves having an active Internet connection (using WiFi, USB Ethernet, Bluetooth, etc.), scanning a QR code for an URL, and letting your phone resolve a URL and download the encrypted package. (There are some offline or no-WiFi/no-Bluetooth ways of doing eSIM provisioning but they are a bit... kludgy, IMO. It's an area of active development.)
posted by Kadin2048 at 7:45 PM on July 2, 2023
As to how eSIMs work... it's complicated. Basically, you are downloading an encrypted program which your phone sends to a tiny "secure" embedded processor (essentially the same as what's in a physical SIM card, properly called a UICC) soldered to your phone's circuit board. That program, when executed, will let your phone identify itself using a particular IMSI (SIM number), and will also perform handshakes against a secret key value which it is programmed never to reveal.
There's a bunch of complexity around the crypto used to obscure the details of the eSIM code package in transit... the whole point of which is to verify that the "eSIM" was issued by someone who was authorized by someone, who was authorized by someone, etc. etc., ultimately rolling up to the 3GPP Consortium, an industry group that "owns" the 4G / LTE (and most 5G) standards. And also that the package can only be decrypted, and the IMSI information accessed, inside of a compliant UICC chip.
Sidebar: This wrapping is similar to the asymmetric cryptography used to sign and encrypt emails using public/private keys, combined with a 'pyramid of trust' system not altogether different from SSL/TLS certificates: except that instead of your browser or OS vendor maintaining a list of "authorities" who are equivalently trusted, in the eSIM world the chain of trust flows down from 3GPP and nobody else: they are God and the root of all trust within the system. They authorize national authorities, which authorize cell carriers (often through intermediary organizations) and eSIM infrastructure vendors, and your phone's embedded UICC checks this trust chain when it receives an encrypted eSIM data package and will only load and execute it (on the UICC) if the chain correctly rolls up to the 3GPP master keys. (If you think this sounds suspiciously like a DRM system... that's because it is! There are some architectural similarities to the BluRay and some modern game-console DRM schemes, including a way to revoke intermediate keys if the 3GPP Consortium or a national-level intermediate decides it doesn't like something that someone lower on the food chain has done.)Anyway, fundamentally it's just a different way of distributing the code that runs on the UICC. Instead of physically distributing disposable UICCs with small amounts of data burned into them (in a way that's intentionally made very difficult to recover), now the same information is distributed electronically, wrapped in encryption such that it's intentionally very hard to recover except by the processor inside the sealed UICC chip.
The upshot of all this is that it's significantly harder (although not impossible) to get an eSIM without some sort of Internet access. You can't buy an eSIM from a disinterested market-stall vendor as easily as you can a traditional "hard" SIM. Provisioning an eSIM usually involves having an active Internet connection (using WiFi, USB Ethernet, Bluetooth, etc.), scanning a QR code for an URL, and letting your phone resolve a URL and download the encrypted package. (There are some offline or no-WiFi/no-Bluetooth ways of doing eSIM provisioning but they are a bit... kludgy, IMO. It's an area of active development.)
posted by Kadin2048 at 7:45 PM on July 2, 2023
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