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The Photographic Science of Detecting Fake Lottery Tickets

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Re: The Photographic Science of Detecting Fake Lottery Tickets

#41

Post by greendestiny »

Natsu wrote: post #40
greendestiny wrote: post #32

Earlier quoted context omitted.

While the result of the PCA is quite well defined, there is nothing well defined about the inferences he draws from that. In the end it shows a marked difference in the suspicious area, but there is no proof that the technique will only show those results on tampered areas. If you can simply run filters until the suspicious area 'looks a bit different' and thats your success criteria, you haven't proven anything.

Neal specializes in this sort of thing. This blog post wasn't written to convince you that PCA (or ELA) work. If you've read his other posts on forensics, you'd see that he always starts with the common tests, then works through the most likely explanations, trying to see what you can rule out and where you should focus. A lot of the time, you can rule things out with common sense (the out-of-order numbers jumped out…

It doesn't matter how good your intentions are if you place human intuition into the loop you will fool yourself.

Re: The Photographic Science of Detecting Fake Lottery Tickets

#42

Post by excuse-me »

tantalor wrote: post #26
kijin wrote: post #16

Earlier quoted context omitted.

Then why did it take so long for them to announce how many winners there were? First they said "at least one", and then they said "three". If everything was stored in a central database, they could have found out the exact figures (and a lot more) as soon as the last winning number was announced. Maybe it's due to lack of coordination between states? Or maybe they need to do fraud checking, etc. by watching CCTV foot…

I doubt they use recordings for fraud prevention. I'd be pretty upset if my winning lottery ticket were denied because the store lost the recording, or never had them. It's just too costly to record every purchase.

They don't insist on CCTV but it's a useful tool.

Actually the major source of fraud in most lotteries is the store owner . For small wins the ticket is taken back to the store to scan it to check for a win, the store owner will tell the buyer that it lost, or that it only won a much smaller prize, pay that out of the till and then claim the prize. Especially in poor/immigrant communities where many player may not speak English or have internet access.

There was a story on here about an analyst for an oil company who worked out the random number sequence for a lottery in Ontario. He also analysed the winning claims and discovered that certain stores where claiming a disproportionate number of middle wins.

Re: The Photographic Science of Detecting Fake Lottery Tickets

#43

Post by gigantor »

biot wrote: post #10

Is it possible to reverse engineer the image such that it passes all tests? Knowing the various algorithms that could be used, what would be involved in constructing the modification such that it doesn't reveal evidence of any modifications? One thought would be to actually render an entire scene in something like POV-Ray. Imagine if something like this rendering http://www.povray.org/community/hof/chado.php containe…

From the comments, you can reprint the ticket with a receipt/laser printer and take pictures of the copy, losing the artifacts. Depends on the length of trouble you would want to go through to reproduce a hard copy document.

Re: The Photographic Science of Detecting Fake Lottery Tickets

#44

Post by sneak »

cuu508 wrote: post #36
biot wrote: post #10

Is it possible to reverse engineer the image such that it passes all tests? Knowing the various algorithms that could be used, what would be involved in constructing the modification such that it doesn't reveal evidence of any modifications? One thought would be to actually render an entire scene in something like POV-Ray. Imagine if something like this rendering http://www.povray.org/community/hof/chado.php containe…

I imagine it would be hard for renderer to fake all subtle qualities digital camera introduces. Things like "colors too clean", "noise too uniform", "geometric distortion doesn't match any existing lens" would turn up. In this specific case I think I'd print a fake ticket with dot matrix printer and take photos of it.

I imagine that getting one's hands on blank lotto ticket paper stock roll is probably beyond the scope of this "hack".

Re: The Photographic Science of Detecting Fake Lottery Tickets

#45

Post by stephengillie »

excuse-me wrote: post #5
FaceKicker wrote: post #3

Slightly related, I was wondering how the actual lottery tells if your ticket is real - do the machines record your ticket's serial number and number(s) chosen and then send the info to the lottery HQ? Or do the lottery machines compute an HMAC of some kind and encode it in the serial number on the ticket itself?

I don't know about this US lottery specifically but in most systems everything is recorded at HQ. Not just the numbers, but the place, the date and time, serial number etc That way they can also check with CCTV. It's an interesting topic in database design because the link to the store may fail at any time (remember lotteries started years ago on dialup) and you must not have an issued-unrecorded ticket at any point…

In the US, each state hosts its own lottery program. Mega Millions and Powerball are programs where states have teamed up to pool their resources and gambling markets.

I've sold Washington State's "lotto" tickets, and you're entirely correct about the reliability of the system - if the device can't connect to servers in Olympia, tickets can't be sold.

CCTV is up to the retailers here, though it's entirely possible that CCTV is a requirement to be an eligible lottery vendor.

Re: The Photographic Science of Detecting Fake Lottery Tickets

#46

Post by K2h »

cuu508 wrote: post #36
biot wrote: post #10

Is it possible to reverse engineer the image such that it passes all tests? Knowing the various algorithms that could be used, what would be involved in constructing the modification such that it doesn't reveal evidence of any modifications? One thought would be to actually render an entire scene in something like POV-Ray. Imagine if something like this rendering http://www.povray.org/community/hof/chado.php containe…

I imagine it would be hard for renderer to fake all subtle qualities digital camera introduces. Things like "colors too clean", "noise too uniform", "geometric distortion doesn't match any existing lens" would turn up. In this specific case I think I'd print a fake ticket with dot matrix printer and take photos of it.

I have worked so hard to completely replace dot matrix that I am actually trying to think were I could get access to one and am coming up blank! Many receipts are now the crappy thermal paper that magically disappers from being left on the dash.. Its like magic in the retailers favor...and just about everything else is laser. Where would you get the dot matrix?

Re: The Photographic Science of Detecting Fake Lottery Tickets

#47

Post by Natsu »

greendestiny wrote: post #41
Natsu wrote: post #40

Earlier quoted context omitted.

Neal specializes in this sort of thing. This blog post wasn't written to convince you that PCA (or ELA) work. If you've read his other posts on forensics, you'd see that he always starts with the common tests, then works through the most likely explanations, trying to see what you can rule out and where you should focus. A lot of the time, you can rule things out with common sense (the out-of-order numbers jumped out…

It doesn't matter how good your intentions are if you place human intuition into the loop you will fool yourself.

That's true, but trivially so. Things that aren't infallible can still be useful, but understanding their limitations is important.

If you read that blog, you can find plenty of discussion of those limitations, for example, how the absence of markers of digital manipulation does not prove that an image is genuine. After all, there are plenty of staged photos out there, images that were framed in a misleading way, etc.

Re: The Photographic Science of Detecting Fake Lottery Tickets

#48

Post by greendestiny »

Natsu wrote: post #47
greendestiny wrote: post #41

Earlier quoted context omitted.

It doesn't matter how good your intentions are if you place human intuition into the loop you will fool yourself.

That's true, but trivially so. Things that aren't infallible can still be useful, but understanding their limitations is important. If you read that blog, you can find plenty of discussion of those limitations, for example, how the absence of markers of digital manipulation does not prove that an image is genuine. After all, there are plenty of staged photos out there, images that were framed in a misleading way, etc…

I'm not making a trivial point though. I believe the tools, techniques and expertise this guy professes in image analysis are modern day snake oil. I just think that he has deluded himself instead of being deliberately dishonest.

Re: The Photographic Science of Detecting Fake Lottery Tickets

#49

Post by Natsu »

greendestiny wrote: post #48
Natsu wrote: post #47

Earlier quoted context omitted.

That's true, but trivially so. Things that aren't infallible can still be useful, but understanding their limitations is important. If you read that blog, you can find plenty of discussion of those limitations, for example, how the absence of markers of digital manipulation does not prove that an image is genuine. After all, there are plenty of staged photos out there, images that were framed in a misleading way, etc…

I'm not making a trivial point though. I believe the tools, techniques and expertise this guy professes in image analysis are modern day snake oil. I just think that he has deluded himself instead of being deliberately dishonest.

How then do you explain the fact that his methods have worked? He has outed doctored photos that appeared in news stories and they have been retracted after investigation.

Re: The Photographic Science of Detecting Fake Lottery Tickets

#50

Post by greendestiny »

Natsu wrote: post #49
greendestiny wrote: post #48

Earlier quoted context omitted.

I'm not making a trivial point though. I believe the tools, techniques and expertise this guy professes in image analysis are modern day snake oil. I just think that he has deluded himself instead of being deliberately dishonest.

How then do you explain the fact that his methods have worked? He has outed doctored photos that appeared in news stories and they have been retracted after investigation.

That's not quite what I'm saying, I don't think his tests are scientific not that they show absolutely nothing (although probably fairly close to nothing with ELA). I also haven't doubted his ability to detect fakes but I do doubt the particular efficacy and explanation of his techniques. There is no doubt using PCA can highlight unusual changes in an image - but there are also other explanations. His famous suggestion that terrorist videos had books inserted into them could simply have been a slightly different coloured spot light.
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