
How does the authentication in the new UK £1 coin work? - jpalomaki
http://security.stackexchange.com/questions/53673/how-does-the-authentication-in-the-new-uk-1-coin-work
======
buro9
There doesn't seem to be a lot of information about it and the speculation is
currently that there is an additive that can be seen through spectroscopy or
light, a luminescence or particle based thing which is visible.

They also mention that iSIS is made of three security types: "overt, covert
and forensic".

So I don't think it's the case that luminosity is the core of the security,
that is just the overt layer.

The keywords they keep using are "integrated", "embedded" and they state that
the coin is "full-plate" and that they can produce blanks (for full-plating)
that have iSIS protection.

They also mention (in the bottom video on this page:
[http://www.royalmint.com/business/circulating-
coin/isis](http://www.royalmint.com/business/circulating-coin/isis) ) that
unlike electro-magnetic signatures that have variability and also can vary
over time (with coin wear), the iSIS has a binary yes/no response: authentic
or counterfeit. It's a signature detection technique and the signature is not
related to the size/weight of the coin.

Is it possible to make the interior of the coin in such a way that a radio
signal bounced off of it would produce a received signal of a certain
signature?

Some of the speculation has focused on patents recognised as being held by the
Royal Mint that dealt with luminosity in the plate layer. I think this is just
one of the security measures, but isn't actually the iSIS method.

~~~
FatalLogic
If it's just a simple additive with a detectable signature, then
counterfeiters could obtain the same additive by grinding up real coins. Then
they could apply a layer of that material to the surface of their fakes.

So I think, as you suggest, they must (also) be using an anti-counterfeiting
method that's more sophisticated than a plain additive. At least an additive
that wouldn't return the same signature after it has been reprocessed by
counterfeiters.

~~~
darsham
The problem is, when pressing the coins it might be difficult or impossible to
apply such a layer properly.

If the verification is done with a part of the electromagnetic spectrum that
somewhat penetrates the coin, then you'll need a very thick, "obvious fake"
layer. I am not a physicist so this is just vague speculation.

------
corin_
Are counterfeit pound coins actually an issue? The only real security measure
they're known for is patterns / text around the rim which dates back to the
days when the metal was valuable enough for people to cut slivers off to melt
down while keeping the coin roughly circular.

I find it hard to believe that anyone with the inclination to break the law in
such a big way, and the resources to do it, would chose pound coins as the
thing to counterfeit. I could be completely wrong..?

Edit: Of course I presume I must be wrong by the fact that this coin is being
introduced, I guess my question is _how_ wrong am I - how is making fake coins
worth the effort?

~~~
GunlogAlm
Yes, it's a big issue here.

From the Royal Mint:

 _The Royal Mint regularly conducts surveys to estimate the level of
counterfeit £1 coins in the UK. A survey undertaken in November 2013 found
that the rate of counterfeit UK £1 coins in circulation at the time had risen
from 2.74% to 3.04%._

[http://www.royalmint.com/discover/uk-coins/counterfeit-
one-p...](http://www.royalmint.com/discover/uk-coins/counterfeit-one-pound-
coins)

And:

 _The move comes amid concerns about the 30-year old coin 's vulnerability to
counterfeiting, with an estimated 45 million forgeries in circulation._

[http://www.bbc.co.uk/news/uk-politics-26632863](http://www.bbc.co.uk/news/uk-
politics-26632863)

~~~
viraptor
Ok, so there's a claim I don't understand: ""One in 30 pound coins is
counterfeit, and that costs businesses and the taxpayer millions each year,"
Mr Osborne continued." \- but if they take ~2M of them out of circulation
every year (which I assume means only a bit more are added), that means we
effectively cancel (using £2.2 trillion M4 money supply in 2010) 0.00009%
inflation. Since the current inflation is at ~2%, this should not even
register. I mean, for others it doesn't matter who produces the new money to
regulate inflation (apart from the problem of someone gaining <£2M from it,
but if that's spread between many parties... who cares?). 35M 1£ coins were
minted in 2013 anyway - I get an impression that the cost to businesses and
the taxpayers would be lower if they just subtracted the predictions of fakes
from the next year's minting.

Happy to be proven wrong of course

(I couldn't find an official estimate of number of coins lost every year, it
would be interesting to look at that too)

(sources: m3 supply data [http://www.tradingeconomics.com/united-
kingdom/money-supply-...](http://www.tradingeconomics.com/united-
kingdom/money-supply-m3), inflation [http://www.tradingeconomics.com/united-
kingdom/inflation-cpi](http://www.tradingeconomics.com/united-
kingdom/inflation-cpi), minted quantities
[http://www.royalmint.com/discover/uk-coins/circulation-
coin-...](http://www.royalmint.com/discover/uk-coins/circulation-coin-mintage-
figures/two-pounds-to-20p-issued))

~~~
Tycho
Well eventually businesses have to take their money into a bank (or similar),
at which point any counterfeits will be removed and destroyed. The business
therefore takes the hit and loses income, which means they also pay less tax.
For a bus company, for example, I'd imagine it would be a significant problem.

~~~
bananas
Bus companies in the UK have big coin counting machines. The total cash at the
end of the route is tallied off at the end of a route against the charge sheet
from the ticket machine which is printed out. Rejected currency is seen as an
operating cost and is handed back in crates to be disposed of. It's also why
you see lots of bus companies giving huge discounts on pre-paid cards etc.

The annoying bit for is that if they accept a high percentage of bad currency
this is tracked and the drivers get disciplined so they tend to try and give
it back as change before the end of the route (which is why you'll sometimes
see them fumbling around in a pocket for change rather than the coin dispenser
fitted to the bus).

Therefore always check the change from a bus driver meticulously!

Also if you know a bus driver as a friend, watch your change too as the total
amount handed back to the mint for disposal is usually less than the amount
collected. Some of it gets stolen usually and pocketed by staff as it's still
pretty easy to use in pubs etc.

Source: I used to write route management and payroll software for bus
companies that tracked this sort of thing.

~~~
pbhjpbhj
Buses I've been on in disparate areas of the UK [England, Scotland and Wales]
have all [so far as I recall] had a coin receiving slot - you put the coins
in, they are held between plates to enable counting. The drive activates a
lever that deposits the coins (in a safe box behind the drivers security
screen I think). The drivers don't get to touch the coins. No change is given.

I don't ride the bus very often, it's a bit too expensive. It seems either
these are being phased out or you travel on buses in posher areas than I do.

~~~
corin_
I also rarely get on a bus, but I've never come across ones where the driver
didn't touch coins in either Oxfordshire or Cambridgeshire (does make it sound
like a posh area thing, but both have shitty areas that buses operate in
too..) nor in London (which I _think_ now requires tickets to be bought before
boarding.. but could be wrong as I've only ever used my oyster card).

------
camillomiller
The formula of the additive is now a secret waiting to be stolen. Interesting
technology, though I don't get why it's introduced today, since it looks like
something that could have been easily implemented 10 or even 20 years ago. So,
why today? Cost effectiveness of the technology? Political decisions?

~~~
k-mcgrady
It's not even being introduced today - it won't be released until 2017. I
believe that's mainly because every machine that accepts the £1 coin has to
adapt. Apparently that's going to cost £20 million.

>> "The formula of the additive is now a secret waiting to be stolen."

True but it's possible that this, plus the strange physical design of the
coin, could increase the cost of counterfeiting to make it unprofitable.

~~~
Maxious
An Australian company was selling "trade secret" additives as an anti-
counterfeiting measure that they said were unique to each client... but were
actually bought in bulk from China and could easily be reverse engineered.

[http://www.smh.com.au/technology/sci-tech/how-the-csiro-
chea...](http://www.smh.com.au/technology/sci-tech/how-the-csiro-cheated-a-
global-drugs-giant-20130410-2hluf.html)

------
A1kmm
If it works how I understand it does, getting the right combination of
substances is probably just a matter of solving a linear programming problem.

As I understand the explanations, the basic measurement is obtained by
illuminating the coin with light of wavelength λ_1, and measuring the
intensity coming back of another wavelength λ_2 - let c be a putative coin,
and I_c_{λ_1}_{λ_2} be the measurement. To detect a valid coin, the machine
has a set of n standard values for a real coin 'C' at a range of (λ_1, λ_2)
pairs I_C_{λ_1_i}_{λ_2_i} for i in [1, n].

To pass, a coin c has to match within a tolerance, i.e. for all i in [1, n],
|I_C_{λ_1_i}_{λ_2_i} - I_c_{λ_1_i}_{λ_2_i}| < ε.

I am assuming that the set of I_C_{λ_1_i}_{λ_2_i}, and the (λ_1_i, λ_2_i)
values will be public knowledge, because they are needed by privately
manufactured machines working with coins.

The aim of a counterfeiter is to find substances s_j and the concentrations in
which to mix in α_j for j in 1..l (to a base that has no fluorescence), so
that the mixture c passes the intensity tests within tolerance. If we assume
the substances do not affect each other significantly, then we can expect that

I_c_{λ_1_i}_{λ_2_i} = Σ_{j=1}^l α_j I_norm_{s_j}_{λ_1_i}_{λ_2_i}.

Using an off the shelf spectrofluorometer (or even a modified coin reader) a
counterfeiter could obtain the I_s_{λ_1_i}_{λ_2_i} for a wide variety of
substances s, which can be normalised to be per unit of concentration.

Given a bank of substances s_j for i in 1..l (the counterfeiter can choose an
l that is large enough to make the attack work), with known
I_{s_j}_{λ_1_i}_{λ_2_i} values, it is easy to solve for a least squares
concentrations vector α. Let A be an l by n vector such that A_ij =
I_norm_{s_j}_{λ_1_i}_{λ_2_i}. Let y be the column vector such that y_i =
I_C_{λ_1_i}_{λ_2_i}.

Let t(A) denote the transpose of vector A. Using the simplex algorithm, solve
t(A)y = t(A)A \hat{α}, subject to all concentrations being greater than or
equal to zero, yielding the least squares solution \hat{α}. If the result is
within tolerance, the counterfeiter has a viable solution, if not they need a
larger or different pool of starting substances.

In practice, they might want to reduce the number or cost of substances they
use. They could use an optimisation method such as a genetic algorithm to find
the lowest cost set (taking into account set size and the price of substances)
that results in an acceptable \hat{α} solution.

Of course, these coins are fairly low value, and in practice counterfeiting
the coins might not be that profitable anyway given the low value of the coins
and the amount of labour needed to get any significant amount of real currency
in exchange for the coins without detection, so someone capable of making a
counterfeit might be able to use their skills more profitably elsewhere.

~~~
oakwhiz
However because this new coin is being touted as very secure and not
falsifiable, people may not catch on to the fact that you are counterfeiting
the coins, because they might just assume that they cannot be counterfeited.
So perhaps counterfeiting the coins would actually end up being profitable in
the end.

~~~
A1kmm
Also, it might even make counterfeit coin production cheaper if it replaces
rather than supplements current detection methods - maybe a counterfeiter can
make a plastic or wooden coin of roughly the right shape and paint it with a
paint containing the appropriate mixture, and then trick a vending machine
into giving them non-counterfeit change.

~~~
kabdib
Usual weight, magnetic and maybe inductance tests apply.

I also wonder about someone's ability to take slices of the surface of a coin
and spread that out over other cheaper coins. I guess you have to randomize
the test, or make sure it covers more than just a couple predictable spots on
the coin.

Anti-piracy is hard.

------
oakwhiz
I wonder what the false negative rate for this coin will be in vending
machines. When the coins are subjected to real-world conditions, will this
reduce the coin's ability to authenticate with the vending machine? If the
coins are being authenticated using a chemical marker of some kind, will the
coins' exposure to other chemicals, dirt, or temperature affect the coins'
ability to authenticate?

------
JoeAltmaier
So, how does this help now? I have a jar of coins (like 1M other people). If a
grocer finds a coin that doesn't 'glow' right, either its counterfeit, OR I
spent one from my jar. So what?

Or we all turn them ALL in for new ones by some switch-over deadline. And keep
finding now-worthless coins in couch cushions, old jackets, bank boxes etc for
a decade and going "Oh, dang!" Not popular either.

~~~
robin_reala
Cash drops out of circulation after a cut-off point in the UK. E.g. the
current £20 note was introduced in 2007, and the previous one went out of
circulation in 2010. If you want to use your coins you’ll have a grace period
to exchange them.

~~~
JoeAltmaier
Talking coins here. They never go out of circulation. Can last decades, a
century even. And a 'grace period' for coins is what I was getting at - they
get stuck places, left for years. Billions will become worthless if there's a
cutoff.

And further, coins are exactly that currency that's supposed to be
intrinsically valuable! The founding myth was, they're precious metal and
that's why they're tradable. A cut-off defies that myth. Unsettling.

~~~
mjg59
This is hardly without precedent - the old 50P was demonetised as recently as
1998. The world appears to have coped.

(And "Billions" \- Wikipedia claims there's an estimated ~1.5 billion pound
coins in total circulation. The overwhelming majority of those are going to be
exchanged during the changeover period, and even after that banks will tend to
accept them for a significant amount of time. There's no way that the amount
of money written off is going to be anywhere near that)

~~~
JoeAltmaier
'Overwhelming majority' is speculation. Perhaps hundreds of millions in
currency will disappear overnight.

~~~
mjg59
Hundreds of millions would require over 10% of all pound coins to be down the
backs of sofas. Does that seem even remotely plausible to you?

------
dhughes
Casino chips use RFID chips and special edging as well as infrared marks.

Now one company wants to use plant DNA in a similar way as ISIS is used in
metal coins. [2010]
[http://www.casinoenterprisemanagement.com/articles/october-2...](http://www.casinoenterprisemanagement.com/articles/october-2010/gaming-
its-dna-casino-chips-go-high-tech)

------
mindslight
It would be easier and more foolproof to just make the entire coin from a
substance that can't be easily created. For example it's really hard to
transmute one chemical element from another, and many are rare, so why not
pick one to use for coins?

~~~
sirsar
Presumably because verifying the composition of the entire coin without
destroying it is a very hard problem.

~~~
mindslight
Choose the element based on physical properties that are easy to non-
intrusively verify - maybe the most dense, non-radioactive, malleable..

Joking aside, I once worked on a device to detect double-photon fluorescing
marker that's probably similar to what they're using, once again aimed at
anti-counterfeiting of various things. It's pretty neat to hit a substance
with IR and have it glow green, and I haven't seen anything similar since. I
still wonder how rare/common substances with this effect actually are versus
their marketing spiel.

------
Zenst
I wonder how long until we get Coins with RFID in them to verify etc.
Certainly make checking and counting coins in shops much faster. Though they
would probably be made out of a plastic by then.

~~~
nwh
How do you know your coin isn't a duplicate of another? You'd need some sort
of distributed consensus to allow you to independently verify its
authenticity.

------
belorn
What about diluted coins using the same fluorescent compound? Take a coin,
extract the metal plating, and create 10 new coins.

