XRays and electronics

"Michael C"

......... Phil

I think you'll find that high energy radiation/particles will discharge flash and EPROM memory cells over time. If the micro in your key is a ROM micro this isn't a problem, however the rolling code will be stored in EEPROM.

Also, remove power (the battery) whilst doing this. The X-ray may induce malfunctions if power is applied at the time.

-Andrew M

circuit in

Depends on a heap of factors, frequency, intensity, distance from source etc,

Some EPROMs will discharge their cells under high UV but not low X-ray but will do so under high X-ray or gamma rays. There are all sorts of solid state issues, the best analogy is, you can push a tennis ball into a piece of tissue and push it out of the way, ie changing from presence to absence, or 0 to 1. But that same tissue will only have a small hole in it when hit with a bullet, the average is that the tissue is still present so a 0 etc. Solid state physics is repleat with effects like that but also with the opposite effects, so it depends on the materials, whether the X-ray photon strikes and ionises an atom or molecule sufficiently to effectively vaporise the tissue etc (I wont stretch the analogy too far).

One interesting thing is that some OTP eproms can be erased with low level X-rays over a long enough period and in the presence of a small bias voltage, I have heard of a case where a b/w monitor had its scan arranged for a spot size, the EHT turned up so X-rays were produce from a region of the centre of the screen, this was hten used to erase or rather upset some cells on an otp eprom so it could have part of its code written with a hack to dump whatever code was left. This would take a huge amount of time, especially as the erasing would be pretty random but I have also heard that some security cells in the early days of OTP could be erased with somewhat less energy than the rest of the array as those cells were in other regions, suffice it to say these parts didnt last long in the market place...

When it comes to (essentially) fixed electronics where there are no EPROMs or EEROMs etc only ROMS then I'd say its unlikely given the types of X-ray sources most of us encounter at dentist, hospital or airport...

Wont compress any hydrogen well though ;-)

How long ago was that?. These days you can use a laser to read each bit right off the chip, this is pretty common when reading embedded eeproms off dead processors.

once, no, a million times maybe. x-rays aren't good for stuff...

cameras, walkmans, laptops, and even car keys go through airport X-ray machines every day, I've not heard one report of damage.

Bye. Jasen

Something like 10 years back, I recall it was a real messy low end way to try to glean the contents, it was in one of the alt hacking forums, seems it was only effective if you really had lots of spare time and lots of chips to wade through...

Are lasers used that much these days, surely its not as simple as that, I read a while ago about glass passivated coatings added to many secure chips especially when SOI or SOS chips are prepared and before any encapsulation, which I would have expected make life very difficult for laser scanning, even in vacuo with electrostatic probes as the coatings effectively clouded the field over the PROM array, think same thing used in FPGA and ASICs ?

Getting the epoxy off is also no easy method unless you happen get some of that Sulphoxide solvent which is highly carcinogenic. I certainly wouldnt try it, these days techniques for data processing are so well known for even the off the wall algorithms, so reverse engineering from known outcomes using up to date tools would be more efficiently and open other opportunities,

Thanks for all the replies. I haven't done my keys because my car won't open without the electronic bit but I have been doing the phone quite a bit. I think I'll use something non electronic from now on :-)

Michael

Cameras no, the film in the camera maybe.

But then everything is digital these days.

the sign I saw posted said anything less than about 3200 ASA (most films are

I've not noticed degredation in regular films after them going once or twice through the x-ray machine.

are

Of course they say that, they don't want to hand inspect every camera. It's not their film after all.

twice

Real tests have shown very slight fogging for well maintained X-ray machines, or large amounts for old, poorly maintained ones. Of course most peoples happy snaps are not that important anyway, so no need for them to worry.

MrT.

Surely the xrays used at airports are significantly lower. Last time I got a tooth xrayed they covered me in a heavy lead blanket and all the staff vacated the room and hid behind a lead filled wall (not something that filled me with confidence:-). They don't do any of that at de iport.

Michael

Which is all very amusing if you consider your brain to be important. Of course you would not expect dental staff to be experts on X-ray radiation though. My dentist can barely manage to get a usable image.

MrT.

I wouldn't say amusing :-)

Getting an xray using film is very difficult and made more difficult by the fact it takes 10 minutes to find out it didn't work. If the patient moves the film can be no good. Digital sensors are much better because the result is instant, the image can be lightened or darkened if it is over or under exposed, the dosage to the patient is about 10 times less and there's no chemicals. The image is also much larger (size of screen compared to a couple of cms) and can be zoomed further. The only drawback is the $14,000 for the sensor (which is apparently just a CCD in a plastic case).

Michael

the

result

Absolutely, (and I saw that SC article too :-) What I can't understand is why it's taking many so long to change. Some were doing it years ago.

Which is about a days work for many dentists :-( Considering the cost of the X-Ray machine in the first place, it's peanuts.

MrT.

I haven't seen that article.

The machine that generates the xrays is only $8000 which I think is pretty reasonable. Dentists do encounter a huge amount of cost running a practice and don't end up with that big an income considering they are a doctor and have started their own business. Their income isn't that bad either but someone could start a restaurant and make a similar income with no education.

Michael

You can't make a blanket statement that the digital image can be zoomed further than the photographic image. If the resolution is there then both can be zoomed in. I would suggest the resolution of the photographic image is an order of magnitude better than the digital. If size really matters then a magnifying viewer can be used. For the other issues mentioned, digital wins.

Cheers.

Ken

I assume you have never tried running a restaurant then. The *average profit* from a dental surgery would exceed the average profit from a similar outlay restaurant by an order of magnitude at least. And the number of dentists who go bankrupt^ is exceedingly small, unlike restaurant owners. (^ even when they do, it's usually because they lost it on the stock market or horses!)

Of course they are well educated, but doctor/dentist income is controlled by the number of people they let in to the course each year. *FARRRRR* less than the number of applicants with high enough entrance scores. Limited supply makes sure there is no competition. In the restaurant industry, the over supply has the opposite effect.

MrT.

Agreed, but we were not talking about photographs remember

Not for the X-Rays I have seen.

Of course, but if the detail is not there to begin with, it doesn't help much.

MrT.

Good point although some digital xray sensors are now meant to be exceeding the resolution of film. When I wrote that it could be zoomed further I was thinking of the kodak xray which has a resolution of 1600x1200 vs most monitors which are 1280x1024.

Michael