[Ssc-dev] Economist article on image verification from Technology Quarterly, current edition.

[Andrew Senior]

(Please don't forward)
Digital imaging: Insurers, publishers, law-enforcement agencies and dating
sites are using software that can detect the digital manipulation of photosMar
9th 2013 |From the print
edition<http://www.economist.com/printedition/2013-03-09>

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 THE photo splashed across front pages worldwide in July 2008 showed four
Iranian test missiles blasting skywards. Released by the media arm of
Iran’s Revolutionary Guard, Sepah News, the picture (right, top) was soon
found to have been manipulated: one missile had been cloned and appeared
twice, evidently to conceal the fact that another had failed to lift off
(see original image, right, bottom). Governments have long doctored photos
for political reasons. In Nazi Germany and Communist Russia, senior figures
who fell from favour were commonly airbrushed out of photographs. Now,
thanks to digital technology, image manipulation is available to everyone,
and nefarious uses are becoming far more widespread.

In around one in 75 insurance claims, photos documenting property damage
have been fraudulently retouched, says Eugene Nealon of Nealon Affinity
Partners, a company based in London that advises insurers. Liz Williams,
editor of the *Journal of Cell Biology*, says her publication rejects
around 1% of peer-reviewed scientific papers after discovering that
microscope images have been doctored to make results look good.
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Many fakes are obvious. But unmasking a sophisticated forgery can require
hiring an expert for days, says Hany Farid, professor of image forensics at
Dartmouth College in New Hampshire, who sometimes acts as an expert
witness. Rockefeller University Press, publisher of the *Journal of Cell
Biology* and other journals, employs a full-time analyst to examine
submitted images, opening them in Adobe Photoshop and looking for anomalies
by adjusting a series of display settings.

Efforts to automate the detection of doctored images are bearing fruit.
Last year Fourandsix Technologies, a start-up based in Silicon Valley,
began selling an add-on for Photoshop, called FourMatch, that determines
whether an image has come straight from a camera or has been manipulated.
It compares the “metadata” associated with the image against a database of
signatures that represent the characteristic ways in which different
devices capture and compress image data, to ensure that the image is what
it claims to be. FourMatch is sold primarily to law-enforcement agencies
and costs $890. But it cannot tell whether a manipulated image has been
slightly tweaked or extensively doctored. So a human analyst is still
needed “in the loop”, says Mr Farid, one of the firm’s co-founders. A
trained eye can spot inconsistencies in shadows, reflections and incorrect
perspective.

Another tool, recommended to insurers by Mr Nealon’s firm, is Verifeyed,
made by a company of the same name based in Prague. Like FourMatch, its
software examines image files to look for inconsistencies in colour,
encoding and compression formats that indicate the use of retouching
software to modify the image. The software costs $899, and Verifeyed will
also analyse large batches of photos on behalf of clients, charging around
$0.07 per image. Its customers include insurers, law-enforcement agencies,
forensics labs, a dating website and a logistics company keen to expose
bogus claims that goods were damaged in transit. Verifeyed’s boss, Babak
Mahdian, reckons that the technology could also be useful to news
organisations that wish to check that photographs are genuine.

Manipulation-detection software is desperately needed in health insurance,
says Mr Nealon. In some countries 2-3% of claims submitted contain images
retouched to “embellish the truth”, he says, making injuries look worse
than they really are in order to collect more money. Only about 10% of
insurers are using software to spot fakery, says Mr Nealon, so there is
plenty of room for growth.

In January a new law came into force in Israel making it illegal to use
images in advertisements that have been retouched to make models look
thinner without printing a disclosure on the picture. Online images are
exempt, however. “We’re not going to correct the whole world,” says Rachel
Adato, an Israeli parliamentarian who sponsored the bill. The “Photoshop
law”, as it is known, has prompted efforts to pass similar legislation in
America.

A feature introduced several years ago by Canon and Nikon, the two leading
camera manufacturers, gives photographers a way to prove, if challenged,
that their images have not been manipulated. When a picture is taken, the
cameras attach a coded signature that is destroyed if the image is modified
and resaved. An intact signature, then, should prove that a photo is
genuine. But researchers at ElcomSoft, a computer-security firm based in
Moscow, have shown that the system is easily fooled. Counterfeiters can
copy an image’s security signature and reapply it after retouching, says
Vladimir Katalov, ElcomSoft’s boss.

Another way to determine whether an image has been manipulated or not
relies on the fact that in a digital camera’s grid of millions of light
sensors, several are usually flawed. Each flaw creates a tiny
discolouration, imperceptible to the naked eye, in pictures taken by the
camera. If the pattern of unusual discolourations in two pictures taken by
the same camera matches exactly, neither image has been retouched, at least
in those areas. But the analysis is complex and time-consuming, says
Anderson Rocha of the University of Campinas, near São Paulo, who provides
photo-forensics advice to law-enforcement agencies in Brazil. His team is
developing software to automate the mapping and matching of discolouration
patterns.

Software can generally sniff out amateur retouchers, says Dr Rocha, but
professional forgeries continue to slip through. This is partly because
skilled forgers keep up with the academic literature on image forensics,
says Siwei Lyu, a researcher at the University at Albany. Forgers now have
the upper hand, he says.

The ultimate solution may be to separate photographers from their
photographs, so that they do not have the opportunity to manipulate them,
says James DeBello of Mitek Systems, based in San Diego. Bank of America,
JPMorgan Chase, Wells Fargo and other big American banks let customers
deposit cheques remotely by taking pictures of them with their smartphones.
They do so using an app provided by Mitek that takes a snapshot of the
cheque and sends it straight to the bank, leaving nothing on the phone
itself.

Codasystem, a French start-up, offers a similar service. Its “Shoot and
Proof” system allows an image to be taken with a mobile device, tagged with
a timestamp and location and then uploaded to an online repository. The
image can then be viewed and downloaded, but the original remains in the
repository, untouched. Any nefarious Photoshoppery can therefore be easily
exposed. Digital technology can, it seems, be used to prove that an image
is genuine—even as it makes it easier than ever for cameras to lie.
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