Linked by Thom Holwerda on Tue 12th Nov 2013 23:06 UTC
PDAs, Cellphones, Wireless

I've always known this, and I'm sure most of you do too, but we never really talk about it. Every smartphone or other device with mobile communications capability (e.g. 3G or LTE) actually runs not one, but two operating systems. Aside from the operating system that we as end-users see (Android, iOS, PalmOS), it also runs a small operating system that manages everything related to radio. Since this functionality is highly timing-dependent, a real-time operating system is required.

This operating system is stored in firmware, and runs on the baseband processor. As far as I know, this baseband RTOS is always entirely proprietary. For instance, the RTOS inside Qualcomm baseband processors (in this specific case, the MSM6280) is called AMSS, built upon their own proprietary REX kernel, and is made up of 69 concurrent tasks, handling everything from USB to GPS. It runs on an ARMv5 processor.

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RE: Comment by shmerl
by Tractor on Wed 13th Nov 2013 11:14 UTC in reply to "Comment by shmerl"
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Indeed, SIM Card have their own OS too.
But they are more secure by design.

SIM Card don't accept "anything that comes from the air". Data must be properly encrypted, using industry standard algorithms (3DES or AES). Just this simple protection makes it immensely more secure than baseband OS.

Now, beyond that protection, these OS are software rubbish. They are safe mostly because they are extremely limited. Someone able to crack (or pass) the encryption layer protection would have no problem crashing the SIM card OS.
But stealing data from it ? nah, that's the hardest part. This is probably the only thing which has been properly designed in these OS.

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