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The Almighty Buck Science

Fighting Counterfeiters With Quantum Money 149

Posted by Soulskill
from the simultaneously-rich-and-poor dept.
the_newsbeagle writes "This article discusses a proposal to create cash that can't be counterfeited by embedding quantum particles in banknotes. A counterfeiter trying to copy a real bill would have to precisely measure all the attributes of the embedded quantum particles — which is impossible under the tricky laws of quantum mechanics (PDF). MIT computer scientist Scott Aaronson, who famously offered a prize for anyone who could prove quantum computers are impossible, said, 'This is science fiction, but it’s science fiction that doesn’t violate any of the known laws of physics.'"
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Fighting Counterfeiters With Quantum Money

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  • by Anonymous Coward

    The day that we are able to control quantum decoherence and noise in currency that goes through a washing machine will be a great day. But I can assure you this is so far in the future economics will be a completely different creature, almost certainly not concerned with currency.

    • I can't remember where I read about this, I believe it was Simon Singh's The Code Book but anyway this was first proposed as far back as 1970 by Stephen Wiesner [wikipedia.org]. It's sort of odd that it reappears every now and then.
      • by TheLink (130905)

        Especially since it's a stupid idea.
        Quote wiki:

        In addition to a unique serial number on each bank note (these notes are actually more like cheques, since a verification step with the bank is required for each transaction),

        If people have to verify with a bank all the time, it's no longer cash. If people very rarely verify with the bank, it means it still can be counterfeited.

        In the real world, real notes being provably unique does not prevent them from being counterfeited.

        If you want to prevent money from being counterfeited you need to come up with a system so that people can check the presented note/coin easily for themselves.

        • by Rei (128717)

          1) You act like this is a world where you either have to do something all the time or never. Doing it "most of the time", which is actually quite easy, is good enough. "Easy" as in, scanners in the bill slots of vending machines, in cash drawers in cash registers, etc if they can be made cheap enough. Also note that if these become cheap enough to use even on $1 bills, then they're cheap enough to use on all sorts of things, which means quantum ID tags turning up all over the place. Which means incentiv

          • by TheLink (130905)
            If you can make it cheap enough, you'll need to put many groups of quantum "dots" on the bill. Because each time you check a group of them on the note, you can no longer check that same group again, you'll have to move to an unchecked group.

            That's about the only way I can see that makes it viable- if it's cheap and you use very many of the quantum stuff per note. Otherwise you will not be able to check the notes frequently enough to make it a danger to the counterfeiter.
  • Sooo (Score:5, Interesting)

    by ae1294 (1547521) on Tuesday June 05, 2012 @04:33PM (#40224659) Journal

    What happens when someone needs to look at the money to verify it's not counterfeit?

    • Re:Sooo (Score:5, Funny)

      by girlintraining (1395911) on Tuesday June 05, 2012 @04:35PM (#40224699)

      What happens when someone needs to look at the money to verify it's not counterfeit?

      They get a cat that might be alive.

      • by icebike (68054) *

        Excellent. A security measure that leaves counterfeit bills intact, and renders real ones useless.
        And when I drown my sorrows over these feline cadavers at the corner bar, the barkeep will tell me my
        money is worthless. New meaning to the phrase dead cat bounce.

        • Re: (Score:2, Funny)

          by Anonymous Coward

          I thought we settled it yesterday that you could just take the dead cat and turn it into a helicopter to raise money.

          • by operagost (62405)
            Once I get my mouse-o-copter and dog-o-copter off the ground, I plan to recreate every Tom and Jerry cartoon with live aerial action.
          • by g0bshiTe (596213)
            No that's raising dead cats, he didn't have any money on that copter.
      • I have one that might be dead.

      • by Tanman (90298)

        At the very least it is possible that it might not have been dead anymore . . .

    • by Anonymous Coward

      The idea is that each particle can be measured in multiple dimensions. One person can measure any one, but not all three. The bank will have a listing for each bill of which dimension to measure and the expected result. Each bill will have a large number of quantum particles to prevent matching by chance.

      This setup is only as secure as the database holding the recording for the bill.

      • by vlm (69642)

        Breaks down to a OTP scheme? Just use scratch off lotto ticket technology?

        One person can measure any one, but not all three.

        This I'm fuzzy on. Only 3 like an old digicash protocol but with only 3 sigs, or 3 as in like 3 dimensions or something?

        • by hajus (990255)

          You can measure the bit in 1 of 3 dimensions. Let's say the bank measured it in dimension x out of x, y, and z. Now if you want to measure it, you can measure it in any of those dimensions. If you measure in x, you don't mess it up, but if you measure in y or z, you mess up the x reading and it gets randomized. Now if you have 64 bits, then you have to guess all 64 dimensions correctly, or you'll mess something up just by measuring it in a different dimension than what the issuing bank measured. Now a

          • At which point anarchists get their hands on a measuring machine and set about fucking up the money supply.

          • by Rei (128717)

            But that's what I'm fuzzy on. So what's to stop a counterfitter from getting one of these bank scanners (for this scheme to be remotely useful, they have to be available for stores, vending machines, and the like... ubiquitous), finding out which measurements for that serial number the bank cares about, and then setting quantum particles in the counterfeit bill that have the correct measurements for the states the bank is going to want to check? Basically, my understanding of what they're doing comes acro

        • by sarkeizen (106737)
          No, not really. It is just a rather impractical way of making a serial number that can't be forged.
    • What happens when someone needs to look at the money to verify it's not counterfeit?

      You can know how much you have, or where it is, but not both.
      Looking at it changes it
      If you look at a counterfeit it will remain unchanged.
      Don't stare at your 401k...

    • by Hatta (162192)

      Before you look at it, it's in a quantum superposition of counterfit and authentic states. Looking at the bill collapses that superposition into being actually counterfit or authentic.

      • by ae1294 (1547521)

        Before you look at it, it's in a quantum superposition of counterfit and authentic states. Looking at the bill collapses that superposition into being actually counterfit or authentic.

        Let me guess, it always collapses into the counterfeit state...

  • by Anonymous Coward on Tuesday June 05, 2012 @04:36PM (#40224723)

    Where they have to use cats instead of the much simpler counterfeit checking pens.

    This will be a profit loser and allergic shoppers will suffer in particular.

  • by Daetrin (576516) on Tuesday June 05, 2012 @04:37PM (#40224741)
    You never know if you still have any left until you open your wallet to check.
  • This article was written by an idiot. You can't measure all the properties of a quantum particle. But so what? You can't exploit it unless you have entangled particles. And it'll be a bit complicated to store your banknotes in total isolation from the environment.
    • by jeffmeden (135043)

      This article was written by an idiot. You can't measure all the properties of a quantum particle. But so what?

      You can't exploit it unless you have entangled particles. And it'll be a bit complicated to store your banknotes in total isolation from the environment.

      You might as well assume that since they mentioned Science Fiction, that nanotubes (perhaps of the graphene variety) are going to be involved here. That pretty much solves everything, so what is it that you are so worried about?

  • If you're tracking the serial numbers of a bill in a database, skip the quantum brainhurt and just do the same thing video game authors and cell phone companies do: make sure the serial number isn't being used in more than one place at a time. Duh.

    Seriously, it's like trying to invent a phaser so you can light a campfire, when the rest of us would just use a match.

    • by jeffmeden (135043)

      If you're tracking the serial numbers of a bill in a database, skip the quantum brainhurt and just do the same thing video game authors and cell phone companies do: make sure the serial number isn't being used in more than one place at a time. Duh.

      Seriously, it's like trying to invent a phaser so you can light a campfire, when the rest of us would just use a match.

      Really. Really? Simply make sure that a certain marking only exists in one place? I suppose you could, in theory, require every single transaction of currency to involve scanning the numbers, then checking the numbers in with a central authority who knows that certain numbers have been sent from shopper to merchant and need to be "re-authorized" for shopper use again. Otherwise I could run off a thousand copies of a single bill and just use them over a few weeks' time and no one would be the wiser. How

      • what about remote areas??? some cash register systems may run the tapes overnight. But tieing up the phone for each transaction??

        What about satellite internet that has lag, small bandwidth and rail fade.

        • by vlm (69642)

          what about remote areas??? some cash register systems may run the tapes overnight. But tieing up the phone for each transaction??

          What about satellite internet that has lag, small bandwidth and rail fade.

          This kind of stuff was figured out for digital cash in the 90s. Look up a dude named Chaum (maybe misspelled) and his digital cash protocols. If you know how SSSS works and think about signing a note 100 times not once when you "spend" and think about zero knowledge proofs then you're about 90% of the way there already.

          "Oh so this is why a digital $20 bill requires 10 megs of memory"

      • by Threni (635302)

        The checking technology sort of exists - credit cards.

        If cash had a random element (a second serial number, for example, with no connection to the first, which would be sequential) then the counterfeiters would have to have the original notes to copy. Otherwise they'd fake it, and when the note was used it would be checked against the database and be shown to be obviously wrong (note 1049242 should have a security number of 194, this one has 188).

  • by Quantus347 (1220456) on Tuesday June 05, 2012 @04:41PM (#40224825)
    This is one of those things that might well work in a limited situation (tracking marked bills to reveal criminal activity, etc) but the cost of Encoding, recording, and (securely) logging every bill as it is printed just isnt something that would be feasible for the majority of bill denominations. Maybe if it was limited to large quantity bills or something...
    • This is one of those things that might well work in a limited situation (tracking marked bills to reveal criminal activity, etc) but the cost of Encoding, recording, and (securely) logging every bill as it is printed just isnt something that would be feasible for the majority of bill denominations. Maybe if it was limited to large quantity bills or something...

      Maybe not, if you balance these costs against the lost value of money due to counterfeiting, as well as having to come up with new money periodically once there's too much counterfeit in play.

  • As opposed to all those non-quantum electrons, protons, and neutrons embedded in there now, presumably....

    From TFA:

    The visionary physicist Stephen Wiesner came up with the idea of quantum money in 1969. He suggested that banks somehow insert a hundred or so photons, the quantum particles of light, into each banknote. He didn’t have any clear idea of how to do that, nor do physicists today, but never mind. It’s still an intriguing notion, because the issuing bank could then create a kind of minu

  • by detritus. (46421)

    I'll stick with gold, thanks.

    • Yeah, nothing like a currency that doesn't scale with a growing population...
      • by operagost (62405)
        That's kind of the basic principle of currency: scarcity. But now we listen to Keynesian bankers who control our wealth.
    • by geekoid (135745)

      Five little words to inform the world you know nothing about economics.

      • Yeah, because it's not like gold* has been the most stable currency in human history...oh...wait...it has.
        But there's no way that gold* has been the currency during every era of growth and prosperity, while fiat currency has been the currency during every economic collapse...what? That's true too? Really?
        Well, I'm sure if we keep up the strawman attacks on the "kooky gold hoarders", people will continue to use fiat currency until we've successfully transferred all of their wealth to banking elites. And th
        • Gold hasn't been particularly stable, since the value of gold is determined by what various countries set it at. EG in 1934, the U.S. government revalued gold from $20.67/oz to $35.00/oz, instantly deflating the dollar.

          Every economic collapse, eh? Clearly the Roman Empire used fiat currency! Also, the crash of 1929 was in no way whatsoever caused by the use of a gold standard. Finally, there have been quite a number of eras of growth and prosperity in which gold was not the standard. EG After WW2 Britain
          • by ka9dgx (72702)

            If gold hoarding is "kooky" why did FDR confiscate everyone's gold? It's a "worthless relic" according to you fiat fanboys... let us have our shiny precious, you don't need it.

          • Gold hasn't been particularly stable, since the value of gold is determined by what various countries set it at. EG in 1934, the U.S. government revalued gold from $20.67/oz to $35.00/oz, instantly deflating the dollar.
            So...because the dollar v. gold is unstable, it must be gold? It couldn't possibly be the dollar? (Hint: it is the dollar). Countries don't set the price of anything, governments do. And what they set is the value of their currency in gold. What FDR did in 1934 was revalue the dollar, by de
      • by Khyber (864651)

        "Five little words to inform the world you know nothing about economics."

        Speak for yourself, oh ignorant one. Keep pushing for fiat currency while the rest of us stockpile what you will ultimately need to live.

        Then you're enslaved to us.

        Well, given your level of intelligence regarding economics, it's probably better off that you're a slave to us.

  • by Anonymous Coward

    I had a wallet stuffed with a quantum money all in a superposition. Unfortunately when I went to a car dealership to buy a Porche cash, the wavefunction of my cash collapsed into a dirt poor eigenstate and I was left destitute and penniless.

    (FYI This is also how stock markets work)

  • And cant be anonymous. Besides if it can be created it can be copied. Its just a matter of making the cost of entry too high to be worthwhile.

  • Looks like someone read one of Chaum's old blind signature scheme papers and some zero knowledge proof papers from the early 90s, then thought it would be cool to store the bits as quantum states instead of flash memory or bar codes (why?) and it got rammed thru a journalist filter to totally screw up the protocol.

    If that is the case, its really important that unlike the journalists interpretation of the protocol, you have like 200 sigs and only break 100 to prove they're all probably real. That is, if 100

  • by swb (14022) on Tuesday June 05, 2012 @04:56PM (#40225001)

    Besides a slight cut in seigniorage, why don't they make American dollars more difficult to counterfeit? Using materials, colors, etc that would only allow the most skilled counterfeiters (ie, North Korea or other groups with state backing) to copy them?

    A lot of foreign currency has different sizes of bills, little plastic windows, metallic inks (or it could be mylar) and so on that would be extremely challenging.

    I know they've tried to make American money more difficult to counterfeit (micro-printing, watermarking, etc) but it seems like people just keep bleaching out the ink and turning $1s into $20s or $100s because its so darn easy, which in turn makes it easier for the pros to turn out really good fakes, especially overseas.

    It's almost enough to make a guy put on his tin hat and try to think up reasons why the government would WANT the currency counterfeited, especially overseas where it would have less impact on the native dollar economy but keep the currency supply large enough to maintain dollar-as-defacto-currency status...

    • by operagost (62405) on Tuesday June 05, 2012 @05:15PM (#40225283) Homepage Journal

      This is a list of all the anti-counterfeiting measures in US currency. People still take fake bills because they just don't bother to check.

              Fiber Embedded Paper. The paper used to print our currency has tiny threads of fibers embedded into the paper. If the bill has no tiny fibers of red and blur embedded into the paper, it is probably a fake bill. Embedding fibers into the paper is one of anti-counterfeiting measures used to make it harder to make fake currency.
              Border Scroll. On the edges of a bill are fine lines in a scroll shape. The thin, fine lines are sharp and clear on an authentic bill. If you try to use a scanner and printer on your home computer to print your own money, the border art will appear blurry and the lines will run together.
              Security Thread. A security thread is embedded into the paper money and runs from the top to the bottom of the bill. It is printed with the currency amount. When held over an ultraviolet light the security thread will glow red. The security thread is one of the ten anti-counterfeiting measures that work the best to stop people from making fake money and devaluing our currency.
              Color Shifting Ink. On the $100 bill, a color shifting ink made with metallic flakes is used. On the $100 logo, the ink color will shift from black to green depending on the angle you are holding the bill.
              Microprinting. Microprinting involves printing in such a tiny font that it simply appears as solid lines but when viewed under magnification you can read the printing. Microprinting is an ant-counterfeiting measure that makes it extremely hard, if not impossible, for the average person to print fake money at home.
              Serial Numbers. Printing serial numbers on currency makes it harder for counterfeiters to forge fake money. In a large batch of fake currency, the counterfeiters may be forced to use the same serial number on all the bills making it easier to spot the fake bills. On fake bills, the serial numbers may not be evenly spaced or sized which is a dead give away that the bill is fake.
              Watermark. A watermark is embedded into the paper during the actual process of printing the paper. A watermark is very hard if not impossible for most counterfeiters to accurately replicate. A watermark is one of the ten anti-counterfeiting measures used to easily distinguish real currency from fake currency.
              Paper Color. The Yellow and Greenish colored hues used paper money makes bills hard to duplicate at home. A counterfeiter will have a hard time trying to duplicate the color scheme of an actual bill.

      • In normal economic times this is a profit center for the US Treasury. Long term rates are historically 4%. Instead of the treasury paying $40 for a 10-year bond, it pays nothing for the equivalent currency as long its is never returned to the Reserve Bank for one reason or another. That is the advantage of being the world's most popular cash currency. Something like $700B fr the $1000B in cash never returns to US banks.
      • it only need to beat casual examination by untrained human eye, and *maybe* beat a few of the measure used by shop to check big bills (only if you counterfeit big bills). The rest of the measure are more for banks to catch the fake money so that it does not circulate forever, and to forbid small scale outfit (aka your photocopier or laser printer) to easily produce counterfeit money. But big outfit , aka organized criminal, will make bills good enough to fool your average folks.
      • by Khyber (864651)

        "When held over an ultraviolet light the security thread will glow red."

        Only for $100 bills. $20 use green, new $50 use yellow. Newer $5 (the ones with purple on the paper) use a blue strip.

        If you're going to say things, at least make sure you're repeating ALL OF THE INFORMATION. Your words will likely cause people to go "No red strip, this is a fake $20!" when reality shows that real $20 bills have a green strip. Also, LOCATION OF THE STRIP IS IMPORTANT (and something you clearly forgot about.) No $20 shou

    • by vlm (69642)

      Hard as it might be for end users to believe, most "dollars" are electronic not paper, so any foolishness going on with paper doesn't really matter in the big scheme of things. Actually, a foreign country spending "new" dollars to import american products is not so bad of a thing.

  • bill validators need to have this tech but outside of slots they will likely cost to much to put in.

  • A counterfeiter trying to copy a real bill would have to precisely measure all the attributes of the embedded quantum particles — which is impossible under the tricky laws of quantum mechanics (PDF).

    OK, so how does this help to authenticate a genuine note?

    • by dgatwood (11270)

      You have multiple properties and you cannot copy all of them because when you read one of them, it changes the others. If the verifier chooses to verify the property that the forger copied, your fake passes. If it chooses to verify one of the other properties, your fake is rejected. Therefore, if each bill has a bunch of these quantum particles and the verifier chooses which property to evaluate randomly, odds are any copied bill will fail. (Of course, you probably also have to allow a certain percenta

  • Finally money will be worth the paper it's printed on. Oh wait.
  • I think we just need to go back to latinum based currency
  • Practically, we do not have a problem with perfect counterfeits that simply cannot be spotted by an expert. In fact we already have an infallible system (serial numbers: we know all the bills in existence and if any duplicates turn up or numbers out of range we know that counterfeiting is going on and that those bills are counterfeit).

    The problem with counterfeiting we actually have is that bills can relatively easily get past retailers and allow the owner to purchase stuff or launder it even if they would

  • by Anonymous Coward

    Is it even possible to store a photon? You can capture a photon. You can scatter a photon. I don't think you can store a photon.

    And really, how do you keep the secret watermark a secret? Once the spec document for the watermark is written, someone will need to make the watermark verifying equipment. And once that equipment is made, it will be sold to someone who is not to be trusted.

  • My bank balance is both positive and negative until I observe it. I simply never observe it. The positive side usually wins.
  • When it costs eight or nine orders of magnitude more to produce the money than the face value of the money itself, that's generally regarded as a design flaw. It's a sure bet that you could absorb a whole heck of a lot of losses from counterfeiting for the cost of inventing new quantum particle manipulation and testing technologies and distributing them throughout a banking/finance system. By the time it pays for itself, you'd need to have currency that can survive commerce via warp drive.

    Separate poin
  • by Anonymous Coward

    Clerk: That'll be $57.50
    Me: This should cover it.
    Clerk: Sir, this is a $1 bill.
    Me: Well it was a $100 bill before you looked at it.

  • How about using gold for money? We already know that it can't be faked, and there are simple tests to see if it is real. Plus there that thing about thousands of years of a solid track record as money.
  • These theory guys would be totally helpless in the real world.
  • Bill collector: Did you send payment?
    Debtor: Yes. Well, at least partial payment.
    Bill collector: What do you mean partial?
    Debtor: I am not sure. I can tell you when the money will arrive, but not how much it is, or I can tell you how much I paid, but not when it will get there. Your choice.
    Bill collector: *facepalm*
  • If I can't measure it well enough to copy it, I can't measure it well enough to verify it, either. And if the verification is fuzzy, then I just need to copy it well enough to pass the verification. Which is always step 1 in the counterfeiting handbook.

  • I never know how much cash I have until I look in my wallet anyway...and when I do I can't figure how fast I spend it!

  • ... against the biggest counterfeiters: the world's central banks.

  • If it were possible to preserve coherence in currency it would require a central database to check so the question becomes what is the point/benefit of this exercise?

    If the semantic is when you check the bill its value must be refreshed then what is the practical difference between quantum approach and simply storing a new validation code on transisters sewn into the note during the checking process?

    Someone hands you a counterfit $100 bill and you fail to verify it. Your screwed with either the quantum or

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