[HN Gopher] The possibility of making money from shredded bankno...
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The possibility of making money from shredded banknotes using
computer vision
Author : PaulHoule
Score : 77 points
Date : 2024-01-20 19:14 UTC (3 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| gwern wrote:
| Upvoted because while the reconstruction is not too convincing,
| it _is_ hilarious that he 's discovered the banks are cheating
| tourists by selling them under-weighted bank note sets & making
| up the difference with random pebbles & concrete parts.
|
| You'd think they'd have no problem being honest about the count
| since they must shred a huge number of bills daily due to normal
| bill lifecycles, or that people would've shaken the containers
| and noticed, but apparently not!
| plus wrote:
| Is it possible that rather than cheating customers, they are
| simply trying to increase the density of the paperweight to
| make it more effective?
| vlovich123 wrote:
| There aren't 138 bank notes in any of them. Even the ones
| that had no stones had only about 82 pieces (the ones with
| stones had about 20). I don't think that's a convincing
| explanation considering the inconsistency in terms of whether
| or not there are stones and the complete mismatch between the
| amount of notes advertised vs how much there actually is.
|
| It would be pretty funny if there was some kind of scam going
| on here where the notes were actually being reconstructed and
| a small portion of each paperweight was siphoned off to
| support the crime (perhaps by diverting whole notes early in
| the shredding process). That could explain why some weights
| had fewer notes with rocks to make up the difference. Seems
| unlikely obviously in reality but there should probably be an
| investigation to figure out why the Hong Kong Monetary
| Authority visitor center is participating in fraudulent
| behavior.
| willmadden wrote:
| It makes me wonder if some of the bank notes were NOT shredded
| and they added the foreign material to make it weigh
| properly...
| tussa wrote:
| Isn't there still an open bounty on reconstructing shredded Nazi
| documents? Perhaps useful on that too.
| almostnormal wrote:
| East Germany Stasi documents.
|
| https://www.stasi-unterlagen-archiv.de/archiv/rekonstruktion...
| tussa wrote:
| Ah yes, thanks!
| akreal wrote:
| Maybe you are referring to Stasi documents: https://www.stasi-
| unterlagen-archiv.de/en/archives/the-recon...
|
| Edit: link to the English version.
| 0cf8612b2e1e wrote:
| In case people do not click the link In the
| 1990s, the Stasi Records Archive began reassembling documents
| that had been torn up by hand by the staff of the Ministry
| for State Security (MfS). This material had been stuffed into
| a total of 16,000 bags.1.7 million pages from 600 bags have
| been manually reconstructed, indexed and archived.
| Additionally, as part of a pilot project, a computer-assisted
| reconstruction program reassembled approximately 91,000 pages
| from 23 bags.
| dmurray wrote:
| > The idea for this paper was discussed with the staff during my
| visit to the Hong Kong Monetary Authority visitor center. The
| paperweight souvenir is currently no longer available.
|
| I was hoping the author managed to buy the last 100 of them and
| is selling them at HKD 5000 each to people who read this paper
| and want to try their luck.
| noodlesUK wrote:
| Like the other commenter I'm amused that they included rocks in
| the shredded notes to make up weight.
|
| I think something like this is unfortunately doomed to fail, as
| whilst there might ideally be approximately 138 banknotes worth
| of mass in there, it seems likely that the shreds are from
| thousands of different banknotes, and the container holds only a
| fraction of each whole note. Therefore no matter how good your
| reconstruction is, you simply won't have the right pieces to work
| with.
| araes wrote:
| While you might not be able to construct the entire banknote,
| there would probably be a high chance of many partial
| constructions. In and of itself interesting from a partially
| complete puzzle perspective. Plus, attempting to match varying
| serial numbers, dates, reference marks, while still having each
| bill vary.
|
| Could probably be improved by doing 50-100 variations on each
| bill to give a general idea of the patterns possible within a
| zone. Such as: This area has 8 possible characters, with 36
| possible entries /[a-zA-Z0-9]/. It has a fixed border with some
| constant pattern nearby. Show all the possible combos and then
| dice up the area a bunch of different ways.
|
| On the partial constructions topic:
|
| You have 350 of 1000 pieces of an image with some known general
| shape.
|
| How much of the image can you reconstruct while still missing
| 2/3 of the pieces?
|
| At the least has applications for image guessing. Also, agree
| on the false bank note contents, and how many people at the
| note shredding office are just stuffing their pockets with bank
| notes and then filling the cylinders with rocks? Great scam
| that probably almost nobody actually checks.
| CapitalistCartr wrote:
| The practical value here isn't in banknotes, it's in shredded
| classified documents. That's the elephant in the room. And it's
| good for advancing pure research.
| nextaccountic wrote:
| Shredding seems the wrong tool if one wants to dispose
| classified documents
|
| Why not incinerating, dissolving in acid, grinding into a
| fine powder, or something like that?
| fifteen1506 wrote:
| Also questioned myself.
|
| My pet theory is big companies first shred and after send
| to be burned (or recycled).
|
| Plus a shredding machine us safer than a fire device.
| flir wrote:
| Cynically, if your insurance company says "4mm cross cut
| and a paper trail to prove it was done", then that's what
| you do. Why try harder?
|
| But yes, paper that's shredded by a specialist paper-
| shredding company is then typically baled up and sent for
| recycling.
| dools wrote:
| I compost all of my sensitive information that arrives by
| mail.
|
| And whenever I need to dispose of something I can't
| compost, like an old drivers license, I cut it into pieces
| and drip feed the pieces into the garbage over the course
| of a few months.
|
| Call me paranoid but I think there will be a cottage
| industry in sifting through garbage once this tech gets
| mature enough!
| 0cf8612b2e1e wrote:
| Considering all of my confidential information has
| already been leaked by some tech entity or another, yeah
| a bit paranoid. Concentrated data is juicier than mining
| trash.
| KennyBlanken wrote:
| Your trash bags are ripped open and co-mingled as they're
| sorted through by workers as it zips by on a conveyor
| belt.
|
| You're being very, very excessively paranoid doing
| anything more than just cutting it into a piece or two
| across the ID number.
| shwaj wrote:
| Lol! I do that with drivers licenses too. I laugh at
| myself as I do it.
| hammyhavoc wrote:
| Putting it on paper in the first place is a big mistake
| because it probably isn't encrypted, it has probably been
| printed (printers are a bit scary in terms of security and
| privacy), there's cameras everywhere including in every
| pocket, and documents are easily duped, exfiltrated and
| observed, and you would likely have no easily-followed log
| of any of that. You also have to trust whoever does your
| disposal/recycling, and where there's people, there's
| dishonesty. Hence "zero trust" as a concept.
| EA-3167 wrote:
| In many cases incineration is _the_ standard, using so-
| called burn bags.
| lupire wrote:
| That's a different problem. In the banknote, case the
| document is known in advance.
| spitfire wrote:
| Each banknote will have a unique serial number. So at least
| some part of the document will not be known in advance.
| Though serial numbers are well structured so you can take
| advantage of that.
| bookofjoe wrote:
| >Seven Years After Embassy Seizure, Iran Still Prints U.S.
| Secrets
|
| https://www.nytimes.com/1986/07/10/world/7-years-after-
| embas...
|
| https://archive.ph/EVbpX
|
| >Among the most interesting papers are shredded secret
| documents pieced back together by the militants that detail
| attempts of the Central Intelligence Agency to recruit high-
| level Iranian officials, ayatollahs and exiles, foreign
| journalists and diplomats either as paid or ''unwitting''
| agents in the months after the revolution in February 1979.
| ok_dad wrote:
| I'm surprised they could put them back together. When I
| shredded top secret documents in the navy when I was a kid,
| what came out into the bin outside was effectively powder.
| Those shredders could shred a broomstick! Literally, I
| shredded a broomstick once, it didn't even slow down. They
| were tall so you had to climb on a ladder to reach the top,
| and they had a massive electric motor that spun a very
| heavy rotor very fast that would powder the documents. You
| threw multiple reams worth of paper at once.
| 0cf8612b2e1e wrote:
| It does seem a colossal failure that a potentially
| overrun location would not have the real industrial
| shredders and instead relies upon the consumer style.
| NikkiA wrote:
| Given this sample:
|
| https://en.wikipedia.org/wiki/Paper_shredder#/media/File:
| Shr...
|
| It doesn't look like the embassy was even using a cross-
| cut shredder.
| ok_dad wrote:
| Oh I guess it was a few decades before I was in the
| military, maybe they didn't have the best shredders back
| then.
| thekevan wrote:
| It depends on what you deem as a failure. We are talking buying
| something for about $13 US and reassembling it to theoretically
| up to about $17,600 US.
|
| Even if only, I don't know, 1/4 of the pieces are there, the
| potential to turn $13 into $4.5k isn't bad at all.
| lupire wrote:
| Solving the puzzle in the computer doesn't reassemble the
| banknotes physically.
| thekevan wrote:
| Uh...correct. The computer tells you if it is possible.
| Isn't that the whole point of the exercise?
| delichon wrote:
| The point is making money according to the title.
| myself248 wrote:
| The limit of two souvenirs per visitor is interesting,
| perhaps they imagined someone would try this.
|
| The trick, then, is to collude with other souvenir
| purchasers, similar to McDonald's Monopoly, so you can
| quickly swap your own duplicate pieces to others who need
| them. But unlike Mcdonald's Monopoly, there's probably no
| rare Park Place that virtually guarantees an instant win to
| whoever holds it.
|
| The bank could do something like that. They could cut all the
| bills in two, and incinerate the left 60% of every single
| bill, so the souvenirs only contain shreds of the right 40%,
| thus guaranteeing that nobody can ever reconstruct 51% of a
| bill no matter how many souvenirs they have. But there seems
| to be no evidence that they're doing this.
| porphyra wrote:
| Over 10 years ago, in 2011, there was a DARPA shredder challenge:
| https://techcrunch.com/2011/12/02/all-your-shreds-are-belong...
|
| I wonder how much the state of the art in reassembling shredded
| documents has advanced since then...
| jhfdbkofdchk wrote:
| I was just thinking about this at lunch today! I have been
| working through the Advent of Code 2020 problems. Day 20
| involves a very simple version of the reassembly problem,
| putting together square tiles with fixed size overlapping
| border patterns. I did the first phase of the challenge "by
| hand," but I was wondering how fast it would be with the recent
| advances in CNNs and Transformer models.
| jrussino wrote:
| Exactly what I though of when I saw the title. I had totally
| forgotten about this! I was fresh out of school in 2011 working
| my first full time job and took a shot at this challenge on my
| own in my spare time with a very naive approach using Python
| and OpenCV; I was way out of my depth but managed to get my
| name on the (very bottom of the) leaderboard :-)
|
| https://web.archive.org/web/20120126014654/http://www.shredd...
| smeej wrote:
| It feels like I'm missing something important. Even if you could
| reassemble them using computer vision, how are you going to spend
| them?
| Detrytus wrote:
| In my country you can go to the bank and ask for the damaged
| banknotes to be replaced with new ones. As for the explanation
| how you come into possession of so much cash then I believe
| normal money laundering practices still apply
| kadoban wrote:
| Why not just tell them honestly? I can't really imagine what
| law you'd be breaking, I doubt anybody thought to make one
| against this.
| Gys wrote:
| The notes were officially destroyed for a reason so putting
| them back together from scraps... Hmmmm
| fsckboy wrote:
| i'm sure if you read your local counterfeiting laws, this
| would qualify as counterfeiting
| resolutebat wrote:
| Why? They're real notes.
| plorkyeran wrote:
| They _were_ real notes. The notes reconstructed from the
| remnants of real notes are not real notes.
| adrianmonk wrote:
| No, once it is taken out of circulation by the
| government, it is not a real note.
|
| It's like revoking a TLS cert. It was once real. Now it's
| not.
| geor9e wrote:
| Nah. Counterfeiting never includes repairing, unless you
| find the most corrupt country to stretch the definition.
| In the USA, the Bureau of Engraving and Printing is who
| would sell the shredded currency (by the ounce) and their
| Mutilated Currency Division is who would redeem it (at
| face value). They are a federal agency so they'd pass the
| evidence to the FBI and charge you with conspiracy to
| defraud the United States.
| geor9e wrote:
| I don't speak Chinese, but the USA sells shredded currency
| too. Here are their Mutilated Currency Redemption &
| Shredded Currency Distribution rules.
|
| https://www.bep.gov/services/shredded-currency-
| distribution#....
|
| https://www.bep.gov/services/mutilated-currency-
| redemption#:...
| kadoban wrote:
| Interestingly it seems to say you have to agree to all of
| that, and that if you break it your agreement to use
| shredded currency may be revoked, but it doesn't make any
| reference to laws or "we'll come arrest your ass"
| language.
|
| That doesn't mean it's _not_ illegal, but it does tend to
| confirm my suspicion that nobody has thought to worry
| about it.
| robocat wrote:
| They check the serial number, and will notice that the note
| was destroyed.
| foreigner wrote:
| The stained glass windows of the cathedral in Winchester, UK were
| smashed in the civil war. After the war they picked up the pieces
| and rebuilt the windows, but they no longer make a coherent
| picture. It would be amazing to use tech like this to reassemble
| them properly.
| geor9e wrote:
| Hmm, they were smashed in the 1640s and rebuilt in 1660, so
| there is probably no record of the original. So it's going to
| be a lot harder than a banknote.
| https://upload.wikimedia.org/wikipedia/commons/a/a2/Winchest...
|
| The lead borders follow smooth arcs, so the glass may have been
| ground down to fit the existing shaped holes, causing a lot to
| be lost.
|
| The caption seems to suggest all of the windows were broken,
| but only one side of the church was reconstructed with all of
| the pieces. So that's 3/4ths lost there, possibly.
|
| I could see computer vision finding the orientation of symbols
| and faces, and gathering similar patterns. I'm not sure how
| much farther it would get though.
| jjcm wrote:
| Off topic: What's the deal with the number characters and the $
| clearly being different Unicode code points than the standard
| ascii characters here?
| adhesive_wombat wrote:
| They're not different codepoints, they're being rendered as
| mathematical markup by MathJax. This rendering includes using a
| LaTeX-esque font rather like Computer Modern.
|
| Arxiv does this presumably because some papers have
| mathematical expressions in the titles and abstracts. For
| example https://arxiv.org/abs/2401.04991
| csours wrote:
| I think the bank might get suspicious when the reassembled bank
| note looks like it was shredded and reconstituted. I guess you
| could say something like "My toddler thought it would be funny to
| shred a stack of money"
| tialaramex wrote:
| For a large amount it's likely that AML checks apply, but if
| you have most (> 50%) of a Bank of England note and can explain
| why they will give you new one instead.
|
| https://www.bankofengland.co.uk/banknotes/damaged-and-contam...
|
| The form says you need to provide ID if it's PS700 or more, and
| they need witnessed ID for PS10 000 or more for AML reasons,
| sadly you can't apply in person so no tearing up banknotes and
| popping into Threadneedle Street to do it on the spot as a
| tourist.
|
| As that link mentions if the problem with your "damaged" note
| is that it was in a dye pack which exploded during your bank
| robbery, that's not an "accident" and you don't get an undyed
| replacement note - you're a crook, if you weren't smart enough
| to give a fake name and address you're getting arrested.
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