Reverse Engineering a Furby | Hacker News Reader

Reverse Engineering a Furby

poppopret.org

103 pointsMoral_26 comments

Whilst some impressive hacks (and especially convincing university staff to lend you their Expensive Toys), my understanding is that the really tricky bit is going from die scans to netlist/circuit diagram, and thence simulation/code extraction.

The Visual6502[1] folks are probably the best example of how well it can be done (assuming you can't afford to pay ChipWorks or FlyLogic to do it for you), but if you're working with a standardish MCU core and some masked ROM, a lower tech solution like the Dangerous Prototypes "rompar"[2] might work.

Probably requires quite a few dies, or plenty of experience in extracting them before you succeed though.

For actually reverse engineering the flash contents, I think it'd be easier to sniff the bus traffic as you probe it, or make a read/write capable emulator that logs what's going on. With the hacked phone-side control library, you could probably build a mostly automated harness to exercise the various settings and see what gets stored in flash.

[1] http://visual6502.org/

[2] http://adamsblog.aperturelabs.com/2013/01/fun-with-masked-ro...

Coincidentally it's very likely the new Furby also uses a GeneralPlus 6502 (CMOS) core.

From the Wikipedia article: "Furbies were banned from the National Security Agency of the United States due to concerns that they may be used to record and repeat classified information."

http://en.wikipedia.org/wiki/Furby

I knew I remembered the GeneralPlus name from somewhere -

"Many Tamagotchis Were Harmed in the Making of This Presentation"

PDF: http://recon.cx/2013/slides/Recon2013-Natalie%20Silvanovich-...

Video (original? talk): https://www.youtube.com/watch?v=WOJfUcCOhJ0

Video (newer talk at ReCon): http://recon.cx/2013/video/Recon2013-Natalie%20Silvanovich-%...

Natalie Silvanovich did this kind of reversing on a few Tamagotchi products with great success.

"A Furby is an evil robotic children’s toy wrapped in colored fur."

If only all technical reviews started this honestly...

It's projects like this that spark me to always go out and try to learn new things. I forget how much of our surrounded world is hackable sometimes, and it really is sad to think I get so caught up I don't think of these projects near as often as I used to. Hopefully this guy gets somewhere :) these writeups are inspiring, interesting, and educational all wrapped into one nice little package.

Are there maybe some JTAG lines exposed on the board?

Maybe these could be used for finding out the contents of the mem chip and the CPU used.

This class of devices is often made at a ridiculously huge volume and the cheapest way possible, so they're very likely to contain one-time-programmable devices with no test / debug lines.

Yet there are labeled(!) test points visible for the I2C lines on the board, and a number of other labels... so the question is, why doing the epoxy stuff while leaving the labeling on the PCB?

Epoxy blobs tend to be more about cheap mass-production than anti-reverse-engineering. If you're getting a custom chip manufactured, it's often easier to just stick the die straight on the board than it would be to have it put in a package, then put on the board.

How is the bonding from the pads on the die to the pads on the PCB accomplished? Sounds easier to do with packaging compared to PCB for me.

Exactly the same way the die connects to the pins on the package (usually fine wire). Then they cap it all.

Epoxy enhances reliability by keeping the chips hermetically sealed. So when your kid barfs on his favorite Furby it still has a chance of working, or gets thrown by the family dog against the wall.

They are fun to play with from a hardware poking perspective.

So, remember that virus that communicates using high-pitched sound? If no, here's an article:

http://arstechnica.com/security/2013/10/meet-badbios-the-mys...

This article says that the Furby communicates in the same way. It would be interesting if the Furby was a vector for spreading messages via this virus. Very, very interesting.

I doubt this (Furbys are kiddy toys, after all); but this article proves that audio is indeed a viable data communication channel for bypassing air-gaps.

lets ban audio

"Furby: Approved for use in non-pressurized compartments of the International Space Station (only)."

New security measure, from now on I will only allow our user to use their PCs in this room.

http://blogs.smithsonianmag.com/smartnews/2013/12/earths-qui...

If anything, data over audio would be easier in an anechoic chamber since you don't have to worry about reverb or background noise.

US Military guidelines do require acoustic isolation of all SCIFs (Secure Compartmentalized Information Facilities). You just need isolation, though; deadening the rooms is not really necessary.

Someone should invent some sort of general modulator/demodulator and use sound to connect computers to the Internet!

Not sure if this is sarcasm...

Oh come on, calling it a modulator/demodulator totally gives it away :)

I like to give the benefit of the doubt but in general I just don't trust comments on HN anymore.

Plus doing it with light is just way cooler.

I've seen something along this line before - but this article is dated for Yesterday.

https://github.com/iafan/Hacksby found via hnsearch.com but I don't think that's where I saw the details last time.

There's this http://news.ycombinator.com/item?id=4984100 too - about open-source furby-like projects.

It would probably be easier to read the chip in-situ with a Bus Pirate and flashrom :

http://dangerousprototypes.com/docs/Bus_Pirate

http://flashrom.org

I used one of these to reflash the BIOS on a logic board after the utility provided died, without removing the BIOS from the board.

Just funny to think that its possible that a dev who hacked on that Furby firmware is reading this and said "hey, I wrote that routine!"

Reply on news.ycombinator.com