[ell-i-developers] Re: FYI: Security protocols in constrained environments

  • From: Teemu Hakala <temmi@xxxxxx>
  • To: "ell-i-developers@xxxxxxxxxxxxx" <ell-i-developers@xxxxxxxxxxxxx>
  • Date: Fri, 21 Feb 2014 08:34:41 +0200

On 21.2.2014, at 7:50, Ivan Raul <supra.material@xxxxxxxxx> wrote:
> Very interesting indeed. But still the size of those libraries is not 
> compatible with the target size of the Cortex-M0, IIRC 16KB. But for the 
> Cortex-M4 I think is a completely different story.

Those slides indeed summarize the TCP story pretty nicely for smallish end of 
embedded design.

I’ve had the gut feeling that we just _may_ be able to fit in the lowest end 
(STM32F03/F05) something that is able to sign messages but that most kinds of 
complicated stuff like stateful sessions with per session asymmetrical keys and 
all that.

Thus, we have to design our system level communications so that the abstraction 
for signing/encrypting messages and paths of communication is optional (for 
decidedly low security) and easy enough to use and implement so that the 
default option for every developer is just to use the S protocols.

I’m in my mind targeting a world where every communications is encrypted or 
signed, and all nodes in a network can somehow be verified to be trustable. Mr 
Moore might make this happen soon enough so that we can use the F4 series for 
even the lowliest nodes of a single pushbutton but I’m not betting on it. In 
the lowest cost nodes we’re basically aiming at our BOM be comparable to a PSU 
without any processor at all, having a special power supply controller chip.

This is very challenging and interesting. We should be getting inspiration from 
guys doing the kind of things everybody thinks are just totally impossible, 
like making an unexpanded Commodore VIC-20 sing.


Now, for those not about to read I’ll summarize the challenge: a VIC-20 has 5kB 
of RAM and a 8bit CPU running at 1MHz. The sound and display controllers are 
nothing much; there is 550 bytes of video RAM and character logic, the sound 
system has three square wave oscillators and a noise generator. Now after 
reading this, do watch the video again.

We’re already doing things commonly thought undoable or at least middle depth 
black magick. Our software controlled power supply is usually perceived as a 
serious WOW thing by people knowing median hobbyist level of electronics. We 
know that in reality a switch mode power supply just requires the designer to 
think in one more dimension but this is already nothing special for any radio 
hobbyist. We’re basically just pushing energy into storage and releasing it 
from there. I’m hoping we eventually run into somebody who can generate a nice 
3D representation of the U/t and I/t graphs that would illustrate the 

Even if applying secure protocols to the smallest MCUs proves out to be totally 
undoable, we’re adding value: now in the world post ELL-i, the power supply can 
communicate to the Internet.

 - t

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