Schneier on Security

Clive Robinson • April 14, 2023 1:32 PM

@ Mexaly, ALL,

Re : 100% call rate on fliping coin.

“With a little practice, you can control a flipping coin.”

I’ve explained how to do it on this blog years ago but it’s easy enough to do.

1, You just flip the coin no need to control this stage.
2, Catch it in a half open catch hand.
3, Surupticiously note the face.
4, Bring it down still covered onto the back of your flip hand.
5, Ask the other person to call.

You know that if you lift your catch hand with the coin still on the flip hand then the other face to what you saw will be upermost, if it matches the call then you just lift the catch hand.

If it does not match then you have two choices,

First is the easy way which is to rotate your hands such that the coin is back in the catch hand and you hold it out to the caller to see. This works for the likes of sports where only a single call is made.

The second way is a little harder and needs to be practiced. What you do on bringing the coin down on the back of the flip hand is to keep it at an angle of about 30 degrees under your catch hand with the lifted edge towards the flip hand wrist. If the up face matches the call then let the coin drop flat onto the back of the flip hand as you lift the catch hand. If not you need to do a “slide uncover” where instead of lifting the catch hand up you move it towards the end of the fingers of the flip hand, and in the process lift the raised edge of the coin and do a half rotate so the down face is now up.

It is harder to describe than it actually is to do and with only a little practice you can keep getting the coin to 100% match the other persons call (or not if you are unkind).

When my son was about 7 I would play the game endlessly with him sometimes for chocolate biscuits, it did not take him long to realise he was only going to win three biscuits (yup I know what other parents are thinking 😉

His junior school had a meet the teachers fun opening even where they had various displays. One of which was a maths table that demonstrated “probability” by coin flipping… Yup his maths teach who was a smart cookie in her own right and quite cute was instabtly fascinated when I showed a 100% call rate, she fairly quickly knew it was a trick but it took her a while to make a guess at how. Other kids who were older said I must be a magician…

Yes, I can do some simple card tricks as well based around things like “the binary chop” though I’m long out of practice.

All such tricks make “ice breakers” and can be way better than “chat up lines” at parties and the like.

Unfortunately the “burning floaters” using “Magicians’ Flash Paper”(Nitrocellulose) are nolonger alowed. Put simply they could be made with the thinest “cigarette papers” or even plain toilet paper that you wash in an acid solution. However they are technically now an explosive so banned… I’ve tried making replacments with potassium permangenate wash and other nitrate washes but they don’t work anywhere near as well…

Clive Robinson • April 15, 2023 7:54 AM

@ Leer, ALL,

Re : Schematic Diagrams.

“Some Amazon reviews are unintentionally hilarious for criticizing the author for not revealing the coding, or mathematics involved, not giving a schematic (!), and not giving a detailed accounting of financial details.”

The Bloomberg artical does give a schematic diagram and they say it is,

“An electrical diagram for a roulette device. Edward O. Thorp Papers/Courtesy University of California, Irvine Special Collections and Archives”

https://assets.bwbx.io/images/users/iqjWHBFdfxIU/i_qwNQHs8arQ/v0/640x-1.jpg

It is unfortunately neither clear or well drawn, the latter indicating some one who was not an electronics design enginer.

However those Amazon readers will gain nothing from it.

It’s not a “computer” but a striped down circuit of a childs “morsecode sender” or “walkie-talkie” with a few changes…

That appears to have been a not overly successful attempt to reduce parts count or size (ie three batteries, when one will do).

Thus I suspect they started with a smaller much more reduced circuit, ran into active usage problems and went down the “Victorian Artisan” route of “bolt a bit on over the cracks” rather than do a redesign.

For those with a yearning to try such a thing, you can find modern versions of such these days look up the “Pixie Transverter” you could buy for around $4 plus shipping not that long ago on those “Online Chinese Market Places”.

There is even a “Pixie History” file with lots of circuits of thirty years of the Pixie history from it’s inception in the 1980’s. You will be able to match parts of the “Thope Device” circuit to them.

The Pixie was designed as a followcon to try and rebuild a little nostalgia for the early “single valve/tube” post war designs.

https://www.gqrp.com/The_Sprat_Pixie_File.pdf

Peter Parker VK3EY has several web pages and YouTube videos on the Pixie, it’s failings and how to “hack it” to improve it in various ways. Helpfully for those less practiced in the art, he explains how it all works and the many things else you can do with it,

https://vk3ye.com/projects/pixiehack.htm

As a result of Peter’s videos, you can “lead the life” virtually vicariously.

However there are better designs like the “Tuna” which is kind of a pun name (from “Tune her up”),

http://www.qrpme.com/?p=TUNAS

The modern versions of which do actually meet the FCC and other regulatory emmisions requirments.

Clive Robinson • April 15, 2023 6:05 PM

@ Leer,

“… anybody asking for a schematic would not know what to do with it.”

Some of us here are oldet than the 6502, and even developed systems around it.

Surprisingly for many, the 6502 core macro is still in use, and you can obtain Apple ][ compatable “Single Board Computers”(SBC). I’ve even still got three working “Tangerine” boards still in a rack mounts with 1/2 Euro Card back planes.

So whilst the number of people who would know what to do, is quite few, wr would know how to port it onto currently available hardware…

It might actually make a fun project to re-do it.

The thing is I doubt the software is as complex as some might think. To get the required speed of response using a 1MHz CPU clock it would need to be quite simple.

I suspect it was little more than a couple or three integrators and the “clicks” would be made against a fixed mark on the rim when the ball or green passed it (otherwise it would be beyond human ability to do unaided).

Clive Robinson • April 16, 2023 4:47 AM

@ MarkH, ALL, JonKnowsNothing, SpaceLifeForm, ALL,

Re : Bolting the door before the horse bolts through it.

“I infer that we’re thinking about different categories.”

You are looking “after the event” and I’m looking to “predict the event”.

To change a wheel / table is an involved process therefor takes time, especially if it needs to be bedded in. Casino’s especially Clubs are looking for minimum disruption at all times as they are a “luxury experience” and their desired participants are “exacting in their expectations”.

Therefore it’s a safe to assume that like other hospitality infustry venues they want to do well “planed maintainence” to minimise disruption thus disruption to income.

But also as a lot of “loss” from a defective is a risk, they want that risk minimised if not eliminated.

So I don’t think they would want
an after the fact rush, where the risk door was open for a period that an alert observer might walk a million or so out of.

Which brings us onto your,

“it’s enough to track the most recent n spin results, where n is perhaps on the order of 100.”

It’s not.

You are assuming a continuous unidirectional drift, not a more likely cyclic or similar drift, that might be “caused” by an observable “effrct” such as where a croupier or others stand…

But we’ve actually been through this before as I’ve repeatedly explained to you on this blog.

Using two drifting oscillators often “ring type” and a D-type latch which Intel and similar use(d?) in their “in silico” alleged TRNG’s that were not. Close in measurment which your “order of 100” is, looks random and will pass most if not all statistical tests on that sample size. However as I’ve explained pull out the timebase and what looks like random close in is absolutly not it’s almost entirely predictable and so exploitable with minimal resources.

Why? Because it’s a 1bit quantitized sampling of a sine wave at the difference frequency between the two oscillators. And is therefore more than sufficiently predictable to be fully exploitable by a very limited range search attack (which is what the neighbour bet does).

We’ve known this for quite some time, and there has even been one or two published papers in the academic community about it.

But we also know for well over a third of a century from medical diagnostic equipment that uses heart waves you also have the opposit problem. To save resources the manufacturers use peak detection and a timer to establish synchronisation with the heart waveform and then a timer offset to measure the desired feature of the wave form. Rather than digitize the entire wave form and find the feature to be measured. The problem is the former method fails and fails badly if the heart waveform is not stable.

So we know close in limited range measurment can not sync thus find what is very predictable wave forms with just a little purtabation, that the human eye can oh so easily spot.

Therefore it can be seen from long known knowledge that your “order of 100” is very likely to fail, and fail expensively for the casino if the attackers know these things.

As Albert Einstein allegedly observed,

“A little knowledge is a dangerous thing. So is a lot.”

But we also know he said,

“I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.”

In security as in science the “evolution” of new attacks starts with “imagination” from “intuition”. Defenders generally at best work with well out of date and otherwise “limited” “knowledge”.

So all the evidence, pointing to the fact that your “order of 100” is going to fail, has been available in numerous conversations on this blog over quite a period of time, that you’ve participated in.

You appear to have missed it thus “left the stable door open”, and thus the sound of distant hoof beats may well have faded.

Clive Robinson • April 16, 2023 11:24 AM

@ FA,

Why is it you fail to read what I write?

Your hypothesis of,

“It takes just 20 lines of python to demonstrate this.”

Has already been negated.

As I said,

“not a more likely cyclic or similar drift, that might be “caused” by an observable “effect” such as where a croupier or others stand…”

And before you argue that is unlikely it’s already been demonstrated.

So whilst a human can observe many things and find many potential hypothesis, your script can not see, it can not hear, it can not touch, smell or taste.

It can only work on what it has been given in ways it has been told to.

Thus the human as an attacker has a clear advantage over a script that was once written by a defender. That script is out of date before it is even written… As Einstein observed there is a lot more than knowledge. Which if you think about it knowledge is by it’s very existance outdated, and fixed on things past.

Clive Robinson • April 16, 2023 2:42 PM

@ FA,

“You just made your usual sneer to someone who didn’t even attack you in any way.”

There is a saying I know you are familiar with,

“Out of the mouths of babies and fools…”.

Which is a shortening of the words of Bostonian proffessor, Dean at Harvard, physician, poet, essayist and polymath Oliver Wendell Holmes. Who’s fame sprungcfrom the poem “Old Ironsides” he later wrote the popular series of “at the Breakfast Table” essays/stories. The shotrned quotr comes from “The Professor at the Breakfast Table”(1859),

“Not only out of the mouths of babes and sucklings, but out of the mouths of fools and cheats, we may often get our truest lessons.”

I think you are neither a babe or suckking, as others will have realised from your track record of poorly disguised “ad hominem” commenting via at best “Strawman” argument.

I guess the ball is back in your court to fumble again.