How the Afghan Girl was Identified by Her Iris Patterns


The remarkable story of Sharbat Gula, first photographed in 1984 aged 12 in a refugee camp in Pakistan by National Geographic photographer Steve McCurry, and traced 18 years later to a remote part of Afghanistan where she was again photographed by McCurry, is told by National Geographic in their magazine (April 2002 issue) and on their website. Here is a summary of how I confirmed for the Society that the above portraits show the same person, by running my Iris Recognition algorithms on magnified images of the eye regions in the 1984 and 2002 photographs.

First I computed IrisCodes (see the mathematical explanation on this website) from both of her eyes as photographed in 1984. A processed portion of the 1984 photograph is shown here. (The superimposed graphics show the automatic localization of the iris and its boundaries, the scrubbing of some specular reflections from the eye, and a representation of the IrisCode.)

Then I computed IrisCodes from both of her eyes in the 2002 photograph. Those processed images can be seen here for her left and right eyes.

When I ran the search engine (the matching algorithm) on these IrisCodes, I got a Hamming Distance of 0.24 for her left eye, and 0.31 for her right eye. As may be seen from the histogram that arises when DIFFERENT irises are compared by their IrisCodes, these measured Hamming Distances are so far out on the distribution tail that it is statistically almost impossible for different irises to show so little dissimilarity. The mathematical odds against such an event are 6 million to one for her right eye, and 10-to-the-15th-power to one for her left eye. National Geographic accepted and published this conclusion in a second cover issue featuring Sharbat Gula, 18 years after the first, and the Society launched their "Afghan Girl's Fund" to assist the education of Muslim girls in cultures that discourage or prohibit female education.

The screen dumps (computer output) that I provided to National Geographic, confirming Sharbat Gula's identity may be seen here. A more detailed explanation about how these algorithms work is available in a 10-page .PDF white paper titled How Iris Recognition Works.



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