Schneier on Security

Clive Robinson • November 29, 2023 11:21 AM

@ Bruce,

Re : The sensors are cheap.

“”

This is easier to explain with a white-board and a couple of coloured pens than by using words. But…

There are two basic types of fingerprint reader,

1, Match on Chip (MoC).
2, Match on Host (MoH).

Both involve a chain of parts and security as always becomes complicated with data in chains of what are Shannon channels due to the two types of basic authentication.

1, Session authentication.
2, Transaction authentication.

Match on chip thus gets favour where information security gets swapped with physical security and the reduction in the effort required to make such a sensor system secure.

Match on chip, is also called Match in Sensor”(MiS), and it’s alternate name tells you that physical security and it’s attendent low cost is what is unfortunately prefered by software vendors. As opposed to match on host.

MoC\MiS tries to integrate all parts onto a single chip, on the assimption they would be easier to intergrate.

That is the MoC/MiS sensors have a microprocessor and storage built into the chip along with the actual sensor and optics which allows fingerprint matching to be performed directly within the chip, thus allegadly securely by physical security… The idea is that Session Authentication can be used at powerup each time rather than
“Match on Host” where it has to be done every time as Transaction Authentication, which is more costly in developer time and effort, but arguably orfered higher security.

What goes on is a process where an assumed good but distorted image of the finger print is turned into a descriptive template of just a few bits in comparison. As the assumed number of authorised users is small these can be stored on the MoC/MiS sensor processor rather than the Host which in theory alleviates some privacy concernces. This obviously allows for user enrollment, matching, drift correction, and removal, all on the chip it’s self. Which obvioulsly opens up a security hole or three unless other bi-directional dynamic secure precautions are taken.

One obvious one to check for would be “REPLAY” attacks which is why Microsoft stared inventing it’s own protocols…

Need I say more?

Clive Robinson • November 30, 2023 3:12 AM

@ Zaphod,

Nice to hear you are still here even if it’s just lurking, I hope you are finding life if not profitable in some way, atleast comfortable and unstressful?

As for me, I’m getting to that time in life, where I still look out with the eyes of a brash and hopefull 20ish something… Then a reflection tells me that my beauty if ever I had some has gone past craggy to something more like knarly. Which for someone who was 2m in their stockinged feet and looking not unlike as once described “A Klingon warrior having a bad hair day” might be seen by some as a “softening of character” 🙁

Whilst I still do atract the attention of nice young ladies, sadly it is in reality that on seeing me they jump up sympathetically and offer me the seat they were siting on. Whilst my joints and healed bones are grateful for the seat, my heart as it were, yearns as it did when I wore a younger mans clothes in places of near bacchanalian leisure to wile a night away, before heroic labours in the light of day, to right wrongs and fight the dangers that others had wraught on an unsuspecting world, with an engineers pencil and slide rule.

The once straight back of heroic pose, is now more like one half of a Norman Arch. Which gets ever more curved as I bridge the years. The question is thus which will happen first, my nose to touch my toes so all I can do is look back, or my joints to cease up so like the “Highland Haggis” so I can only walk in small circles around the mountains of life?

But there is a lot to be thankfull for, such as escalators in shops and cinemas, not that anything is worth buying or watching, but they are warm and dry with coffee shops where the smells remind you of exotic little shops that roasted beans to order. Back when young enough that trousers were “above the knee” in all weathers, you could stand outside strange little shops and breath the aromas out of the roasters and almost float. But we also used to get fogs so thick in early october that if you shone a flash light at the ground the beam would not get there. Snow happend in December, not as now occasionaly at Easter. But also the blessings are mixed, whilst we still get “misty mornings” of frost so sharp it cuts your breath harder than a neat malt, the fallen autumn leaves nolonger crackle under foot, they are slimy and slick like oil on ice, a hazard for even the most agile of feet. Likewise when you draw open the curtains you might see condensation beading, but there is no “jack frost” feathers on the glass. And the wind nolonger howls in the chimney and hot water runs from the tap as pipes so rarely freeze, but nor do ponds in the park or rivers such that you could walk across and fires are nolonger alowed so you miss the comfort of cuddling in front of one.

Now young heads touch together as they stare at screens in their hand it would be nice if it only happened when they were seated side by side on a sofa, but no it happens as they walk down the street… Yesterday I went out to get a couple of things from the shops… Within ten minuites I’d been nearly bumped into three times and one little twit actually bounced off me even though I’d stopped and was standing still.

Such things tell me I’m getting “crotchety” which is not a good sign, I’d probably soon be “shouting at clouds” and waving a walking stick in the air if I had one. I instead have elbow crutches and it just does not work with them, I know I’ve tried and it looks silly 😉

Things still go up and down but now it’s my blood preasure, cholesterol and all sorts of other scary words the doctor utters that go up, and it’s the tablets they prescribe that go down. I’m due a dread “drug review” that generally means I have to try and remember another couple of made up words like “Dapaflaperine” or “Oxyisinthebandriveragain” and woebetide you when the eternal crumdgin pharmasist in the hospital comes around and you get just one syllable wrong, needles are not the half of it. You end up feeling like the small child that says they know how to spell banana but they don’t know where to stop =(

I’m reminded by the sound of sirens on the main road that “chest disease” time is back and hospitals are not the place to be anywhere near. A bad cold or worse the full on flu was about the worst missery most in the West would suffer, now the Drs are telling me I should have a jab for this and a jab for that and then give me a bill for acupuncture…

Yup I guess you could say it’s all going well 😉

Clive Robinson • December 1, 2023 2:50 PM

@ Anon E. Moose, ALL,

Re : Gaps don’t all have to be air.

“so physical security is still paramount…”

Yes and probably always will be, even though informtion security via the like of encryption are assumed to be stronger.

The reason is,

1, Without access an attacker has nothing.
2, With access an attacker can read and copy information.
3, With a copy an attacker can use as many resources as they have to best attack encryption.

Now consider that it’s your laptop you are protecting.

When it’s in your close possession if someone trys to get physical access then you will be aware of it, or aware you unexpectedly lost consciousness etc.

If you lock it up in an appropriate safe, then physical tampering to the safe etc will be visable.

If you leave it in a hotel room with an appropriate box of tricks anyone coming close or just touching it will set of an alarm.

At which point you can assume the data has been copied and at some point in the future become of use to the attacker.

The problem with modern laptops is that like modern cars they are being forced to be wirelessly connected to function. This is obviously very bad news for many reasons.

Which is why some people are building the equivalent of Small Personal Assistants of the last century with the likes of “Single Board Computers”(SBCs) or even high end microcontrolers as “Systems on a Chip”(SoC) where connectivity is very strictly built out, not in.

The thing is most of our laptop computing power is not used for anything particularly usefull for most people. Yes graphics and video and games are nice, but the command line is fine for data entry and in most cases reading data back. It’s only when we format it in some graphical way does data start to need the display etc of a mid 1990’s to turn of the century computer.

Since then most of it has been for gimicks, games, girls, and gambling (The 4Gs).

From a security perspective minimising,

1, Communications of all types.
2, Minimisation of code.

On systems is a good idea, and physical access comes under the first.