Truphone makes a reprogrammable SIM

MWC 2013: All calls are local because all SIMs are local

Truphone logoYou know all those things that annoy you about mobile phones and roaming, especially internationally? It looks like someone is actually doing something about it, and that someone is Truphone.

I admit that I had seen adds for Truphone a few times, and from the claims they made, it sounded like a scam. Low or no premium international roaming? Local calling from every country you go to? Multiple numbers, one for each country you go to? Inbound calls to any of those multiple numbers ringing through all as ‘local’ calls no matter where you are in the world? All this and non-roaming home country calls at reasonable rates too? Sound like a scam to you? You know, the kind where once they get your credit card you are going to be hit with crazy fees every time you take your eyes off the bill. Having talked to Truphone at MWC about their tech, and now having used it for a while, I can assure you it is anything but a scam, it really does do what they say, with a few fairly minor caveats.

There are two problems with getting decent rates internationally and having multiple numbers, phone company greed and SIMs that have locked identities. Greedy evil phone carriers are nothing new. Given the state of modern politics, don’t look for that to change any decade soon, at least for the big guys. SIMs are hard locked for all the right reasons, mainly to prevent spoofing, crime, and other sorts of things you don’t want happening to you. Trust me, this is a good thing.

Truphone solves the greed thing by being small and having a very different business model. The business model is different because they try to offer you services that you want and need which the others can’t, and make money by doing things that no one else is. The SIM being fixed to a single value is the technical root of the other problem, and how they solve that one is the really interesting bit. Yes their SIMs are not static, Tru can change the identifying values the SIM gives the networks as needed. How they do this, and how it is kept secure is the heart of this story, and it is quite neat.

At the heart of Truphone is the SIM, that is their product. They call it the Tru SIM and unlike all the other SIMs out there, it can be reprogrammed on the fly. This ability may seem trivial, but doing it right is both an incredibly complex technical undertaking and anything but as straightforward as it sounds. This may seem like it opens the door for scammers, but doing it securely is the problem that Tru looks to have solved.

Enough with the huggy-kissy stuff, technically speaking, how does it work? Some of it falls firmly in to the, “we can’t tell you” category but enough detail was given to get a fairly clear picture. You are probably familiar with a normal SIM, they have some hard coded numbers called the ICCID and IMSI plus storage for 250 contacts. There are other under the hood options like storage for preferred carriers, temporary ID codes, and all of that, but in theory, the two core identifying codes are inviolate. This is for a very good reason, if you can spoof that, you can spoof just about anything on a cell network, and that is not good for users or providers.

To offer the services that Tru wanted to, essentially allowing the unchangeable to be changed, for obvious reasons they couldn’t use a normal off the shelf SIM. So they made their own and cunningly called it the Tru SIM, and as you might have guessed, it is re-programmable. The tricky part is keeping this system both secure and compatible with the existing GSM infrastructure out there, not to mention not pissing off all the big phone companies that could likely throw enough lawyers at Tru to keep them tied up until the sun burns out.

Unfortunately you can’t just download an app and type in your own ICCID and IMSI numbers, that would lead to some fundamental problems like how the carriers identify you for basic cell functionality. The Tru SIM is only programmable from the network side, as far as the phone and the user is concerned, it is just another plain old SIM. To keep it secure, all of the data is passed over the GSM signaling channel and encrypted with all of the normal GSM security features. If you are aware of how secure GSM is, the phrase “isn’t” usually comes to mind first, a fact not lost on Tru. Because of this, they also uses their own encryption mechanisms over this, but won’t specify what or how. Both of these things are probably a good idea.

This gives Tru a whopping 2-300bps of bandwidth to the SIM, plenty of speed to send the 3-4 dozen digits needed to update all the “permanent” info on the SIM in a reasonable period of time. If you can’t see where this is going, when your phone pops on to a GSM network, it’s location is known definitively by the the towers it is connected to. While this isn’t anything like GPS level accuracy, if you are only looking for what country the phone is in, this is more than adequate accuracy. When the carriers negotiate whatever dark secrets they do to get you on the network, authenticate identities, bill properly, and all of that, Tru can update any of the identifying info on the fly to seem local.

Whether the information is already stored on the SIM and just selected at the right time/location, or it is downloaded and reprogrammed from the network is irrelevant, the end result is the identity your SIM presents to the network can change. This is where the magic starts, Tru essentially takes your SIM and for all intents changes it to a local SIM on the fly as soon as it hits the cell network. When you take your phone to another country, you are not roaming internationally because your SIM makes it seem like you are a local. This is how they can promise cheap international rates, you are always in your home country.

Tru does not have an international network of cell towers, in fact they do not have any cell towers. The technical term for this is MVNO or Mobile Virtual Network Operator, and there are lots of them all over the world. MVNOs have agreements with carriers that do have towers, spectrum, and all the physical infrastructure in place to carry their signals. Tru has this type of agreement with most countries, but recently got their wrists slapped by the British ASA for claiming to be “global”. It is worth reading their response to getting called on this advertising slight of hand.

This isn’t to say that Tru doesn’t have real infrastructure, they do. Once the call is connected, it is handed off to a Tru MPLS network as quickly as possible. Sometimes it is at the cell company’s tower, gateway, or farther down the newtork, but they claim it is never any farther than the country border. This is all dependent on the carrier they are dealing with in the specific geography, but it is always transparent to the phone user. Tru also has two geographically separated network operating centers and support lines as well. From the MPLS side of the network, they are a true international phone carrier.

What you end up with is two classes of international roaming. If there is a fully reciprocal agreements in place, you are charged truly local rates when you are in or calling to a “Tru country”. While their web site lists three countries where a user is 100% local, The US, UK, and Australia, but that appears to be a bit out of date. SemiAccurate was told Hong Kong and the Netherlands are on board, with five more countries coming really soon and more to follow. At least in those five countries, calling or receiving calls, you are charged strictly local rates.

That brings up the other interesting thing, the phone numbers that you have. As most people realize, a cell phone has one carrier assigned number. Truphone doesn’t play that game, they simply can’t if they want to offer local rates for inbound calls. When you are roaming, you are assigned a local number. Depending on your plan, you can have multiple numbers assigned to your phone, one for each country. Better yet, they are all live at the same time. Since they control the long haul networks internationally, accomplishing this is nothing more than a couple of lines of code for a shim and a lookup table.

Say you have a US, UK, and Hong Kong number, and are local to the US but in the UK at the moment. If someone from Hong Kong calls your Hong Kong number, it will ring through to your phone in the UK and both sides will pay local rates. Better yet, if you call the US from the UK, it will show your US number on the caller ID, and again, local rates all around. Depending on what numbers you have, where you are calling, and the agreements Truphone has in that country, it intelligently picks the most appropriate number and uses it for whatever you are doing. If this sounds logical, well it is. If you are wondering why this isn’t standard practice, think about how much money the cell carriers make from roaming or worse yet international roaming calls, it is a big number.
In addition to the five listed Tru Countries, there are agreements in place for discounted calls in a large number of other countries. These discounts vary quite a bit, but they are vastly better than what you would pay while roaming internationally with a normal SIM. You can take a look at the rates for a “US” phone here, and other countries are listed if you dig on their site a bit.

As it stands, Truphone has two types of plans, a prepaid SIM for consumers and monthly plans for businesses. Their rates are in the right ballpark for pre-paid plans, but if you don’t travel or call much internationally you can get far better deals. If you do however travel to, call, or get calls from any of the listed countries, it suddenly makes a lot of sense. If your company has a branch office in one of these regions that you regularly deal with or you have family in one of these places, a slight per-minute premium suddenly becomes a massive savings. Simply having a “local” phone for contacts in multiple countries should make it a no-brainer for many people, as soon as one country in particular qualifies as Tru, I might just have to switch permanently.

Once you wrap your head around how it all works technically, the pricing makes a lot of sense. The hard part is reprogramming the SIM from the network side, a non-trivial technical challenge. Next up is cutting deals with hundreds or thousands of phone carriers in hundreds of countries, a thankless task if there ever was one. Both of these jobs are already done, the SIM reprogramming does work, and deals are in place for 220 or so countries. Now comes the fun part, and you can probably guess that multiple live numbers is only the beginning. While Tru personnel won’t specify next, they do smile when you ask that question.

That brings up probably the most important question, does it work? Last week I was at MWC in Barcelona, Spain, and ran into Truphone. They gave me a SIM to try, and I did. I put it in one of the phones I was carrying there, a Motorola RAZR I running Andriod 4.04. Once I set up an account on the Truphone site, other than the normal, “I sense a new SIM” messages, it worked normally without a hitch. Voice worked, data worked, and calls to the US showed the US number I was assigned. I know because I tested it both on the person next to me who had a US phone and my wife who was thousands of miles away, both of which reported the same number on their caller ID. Stopping in the Netherlands on the flight home, as well as once back in the US, everything just worked.

Tru warned that there was one problem on newer versions of Android, some of the data that needs to be changed is now placed in a secure area and can’t be modified without user intervention. The fix for this was to either download their app or manually set the APN, neither is what you would call a high hurdle. I dutifully downloaded the app called Tru APN, ran it and it immediately crashed. A little bit of sleuthing seemed to indicate that the problem was rooted in the fact that the RAZR i was an x86 phone. Dealing with ARM emulation in a secure area of the phone’s OS may cause problems, but as of this writing that hasn’t been 100% verified. That said, adding the APN manually took all of 30 seconds, and from that point, everything just worked. This was the most problematic part about using the Tru SIM, the rest was totally transparent.

So far after about a week of playing on the Truphone network, there isn’t much to report. Their web site works, no problems to report, and three countries were traveled without a hitch. The only open questions now are, “Would you buy one?” or, “Would you use it as your main phone company?” For me the answers are, in order yes and no. Both answers are a bit more complex than that single word though, and are likely different for every potential customer.

I would buy one for the simple reason of convenience, for the majority of countries I travel to, it is cheaper than my current phone company, Sprint. If I was staying in any country for more than a week or so, or if that country was not in the Tru Countries list, I would probably buy a local SIM. Given that most of the places I travel to other than Taiwan are in the heavily discounted range, I would buy one of these SIMs and forward my main local number to the Tru local number. Even as a universal backup, it is worth having.

Not using Tru as my main phone company is pretty easy to explain, it is more expensive than what I have for everything in country, especially data. That pretty much relegates it to secondary status on price alone. If I had an office or a colleague in a foreign country that was covered by Tru as local, picking up a local number and using as my main phone would be a no-brainer. Just the ease of not having to use Skype for these calls is worth it on convenience alone. For remote office workers too, it seems to make just as much sense especially with Tru’s corporate plans.

However since I am not in any of those situations, using Tru as my primary carrier doesn’t make sense. That said, after using it in Spain at MWC for a week, and for a few days since I returned, it is a keeper. I have one SIM for Taiwan, one for the US, and now Tru for the rest. It will make layovers in foreign countries a much less annoying experience, especially for what it saves when you receive calls. Whether or not it makes sense to you is likely case dependent. The one thing I can say definitively is that they are doing a lot of things that were considered flat out impossible just a few months ago.S|A

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Charlie Demerjian

Roving engine of chaos and snide remarks at SemiAccurate
Charlie Demerjian is the founder of Stone Arch Networking Services and is a technology news site; addressing hardware design, software selection, customization, securing and maintenance, with over one million views per month. He is a technologist and analyst specializing in semiconductors, system and network architecture. As head writer of, he regularly advises writers, analysts, and industry executives on technical matters and long lead industry trends. Charlie is also a council member with Gerson Lehman Group. FullyAccurate