My take on how Smart Plug n Talk does it.

Hmm, this blog should have been posted December last year, however I was not able to finished it. So here it goes..

December 2008, Smart launched it's Plug 'n Talk service. The premise of the service is to use your Smart SIM to call and send SMS over the Internet without your GSM phone. So how it is done?

Dissecting the service, it has SIM authentication over IP, voice call and SMS. The voice call is VOIP, while the SMS is the same SMS but the medium of transport is IP.

However, to make use of the SIM, like be able to call from PC to Mobile and vice-versa and at the same time get billed from the SIM's load (yes you still need to top-up the SIM to use the service-- it is not free :D ), the SIM should be authenticated and register in the mobile operator's system. To authenticate the SIM without using your mobile device and still be online on the mobile network perspective,the technology EAP-SIM could be playing in this scenario. EAP-SIM is Extensible Authentication Protocol for GSM Subscriber Identity Module.

EAP have been around and used in the other wireless technology, the WiFi for wireless and even for wired system.

Since it connects and authenticates over IP to Operator's GSM network, there should be a gateway between IP to SS7.

The authentication server could be a RADIUS server that authenticates, authorizes and accounts the SIM usage over IP. This is almost the same with the HLR (Home Location Register) of the mobile network.

So how? In GSM network HLR database holds the IMSI and the MSISDN (acronyms used in mobile domain), the mapping of the actual dial-able number and the unique number inside your SIM plus the shared secret key called "ki"and other subscribers information. So when a SIM gets online by powering your mobile phone, it authenticates through the HLR.

In WiFI or in fixed network, the access control is done on controlled port access device. i.e. wifi access points, LAN switches, firewalls or even routers. They are called the authenticator.

While software needs to be installed or configured on the client side. This is called the supplicant (Smart Plug n Talk). Until the client is authenticated, the supplicant can only communicate with the RADIUS Server using the EAP. EAP supports variety of authentication methods including EAP-SIM authentication.

So a RADIUS can be the gateway between IP netwrok to GSM network. This RADIUS server somehow acts as a VLR (Visitor Location Register). So the SIM looks like in roaming mode.

So when inserting the Plug 'n Talk (with SIM) to notebook or desktop, it authenticates back to GSM network of Smart through IP based AAA server (RADIUS) that acts as VLR and gateway. This communication passes through IP, the basic language of the Internet.

So there it is, my take on how possibly Smart is doing it. Don't ask me the details for it is not as easy as you might think. :)

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My Fourth and my Last, my Retirement Company

The startup bug have bitten me again. This is not due to boredom with my current company but it is a destiny that have started to unfold since 2004. That was the time I read the book "The Alchemist" by Paulo Coelho, a quote in that book really hit me.

"To realize one's destiny is a person's only real obligation. All things are one. And, when you want something, all the universe conspires in helping you to achieve it."


It is another journey for me, a journey that I want to see the destination. I want to retire on my 47th Birthday and travel together with my family.

The universe is conspiring since that day I read the book, but it has a slow start and just started to show some steam just recently. Everything seems falling into place. There will be trials and more trials but I guess I have gone thrice humble with the last three and that I think I deserve a break.

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The movie "Untraceable"

I saw the movie 'Untraceable", a serial killer movie starred by Diane Lane. Diane is cybercrime specialist FBI. The serial killer is a very talented criminal, knows programming, electronics, DNS hacking and other stuffs that is so hard to believe he can do it himself. While killing his victim, he video stream it over the Internet.

What really catch my attention is the DNS exploits he done, the movie was release January 25,2008 and while in real life there was a security advisory about DNS cache poisoning just early this month. It means that any cracker/hacker out there can basically alter the legit traffic of a server to a bogus one. Imagine a ecommerce server, payment system and credit cards.


While in the movie, the hacker was able to "owned" thousands of machine running DNS and dynamically changing his machine IP address (warning: geek speak). This made the FBI impossible to track the killer down. The killer only allow US viewers only, blocking foreign IP addresses. The FBI doesn't even know what to do on tracking this serial killer. They didn't even talk to ISPs or NAPs, or the CERTs and CSIRTs, Domain Registrars.

DNS records needs to be propagated before it become the new IP address gets reflected, the killer video streaming change IP address automatically and gets it working after FBI blocked the current IP address. Can it be done? hmmm

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