Interfacing nasty stuff with MySensors

[RJ_Make]

Interesting...

[hek]

scary...

[Anticimex]

Quite striking stance of opinion on surveillance between American and Swedish here :)

[mikeones]

That usb housing is pretty sweet. A nice shell for a PIR and Temp sensors.

[Anticimex]

Yep, although temperature will probably be skewed due to the heat dissipation of the transformer. But motion and humidity should work nicely.

[tbowmo]

Definitely interesting :) but also a bit scary they didn't think more about security when they created the protocol.

But then again, a good point to not have an wireless keyboard...

It also puts things into perspektive with mysensors, and security.

[Anticimex]

I am already on that aspect. I have implemented support for a security chip which can sign messages using SHA256-HMAC. Eventually I will look into integrating this in the library. The scheme will protect against both man-in-the-middle as well as replay attacks and it will be using a secret pre-shared key.

[tbowmo]

@Anticimex said:

I am already on that aspect. I have implemented support for a security chip which can sign messages using SHA256-HMAC. Eventually I will look into integrating this in the library. The scheme will protect against both man-in-the-middle as well as replay attacks and it will be using a secret pre-shared key.

What chip are you using for the security?

[Anticimex]

Atmel ATSHA204 single wire variant.

[tbowmo]

@Anticimex said:

ATSHA204

Hmm.. will your work be compatible with the full i2c (8pin) version? (I already have other i2c devices, so could just use the same bus). Or could it use any available I/O pin on the atmega?

thinking if I should drop one on to my sensor board (or at least make a footprint for it), just for "future plans"

[Anticimex]

Yes and no. The library I use is for single wire. A new lib (or better, an extension to the existing) is required for I2C. But the logic layer can be reused assuming the api is kept intact (which it should, as there are no hardware specifics in the api). I considered using I2C, but rejected it in order to be able to be more versatile and less dependent on pins and components. But the device register map is identical between the devices so it is enough to switch the data marshaling parts.
The library is based on this:https://github.com/jimblom/sha204-Breakout
But I have made a few changes to it to make it more suited for device use. You can find my lib in the development branch of the MySensors git by now. It also carries a sketch to personalize the device.