IEEE Spectrum October, 2013 - 14

OCT 2013

nORTh aMERICan

SPECTRUM.IEEE.ORG

Last year, the Hoover Dam
hydroelectric plant installed
the first of five wide-head turbines. These are designed to
work efficiently even as the Colorado River
shrinks under a record-long drought. The
dry spell affecting the dam's power source
has outlasted any other in the 77 years that
the structure has generated electricity. By
the time the fifth turbine is installed in 2016,
Hoover Dam will likely need them all.
Lake Mead, which sits on the border between Nevada and Colorado behind Hoover
Dam, is expected to drop 2.4 meters in 2014,
as less and less water flows downstream
from Lake Powell, which straddles Utah and
Arizona. The sharp decline comes about because the U.S. Bureau of Reclamation needs
to cut Lake Powell's water release by nearly
1 billion cubic meters to 9.2 billion m3 for the
2014 water season, the smallest release since
the lake was filled in the 1960s. The flow of
water to Lake Powell from key tributaries has
been decreasing for more than a decade, and
the bureau's forecasters expect that the reservoir could hit an all-time low this season.
"This is the most extreme drought since
measurements began in the early 1900s,"
says Jack Schmidt, a professor of watershed

Previous PaGe: CloCkwise from ToP lefT: GooGle; universiTy of sTraThClyde; TiTan aerosPaCe CorP.; kymeTa CorP.; o3b neTworks

you any insight into how the original
flaws to hackers. When app makers
software works," Sahai says.
issue security patches, hackers often
In the scheme's current version, grab them and quickly dig into the
obfuscation requires too much com- code to figure out a system's Achilles'
heel, uncovering the vulnerability
putation to make it feasible, but its
that the patch was designed to fix.
developers think a practical version
"The crucial technical goal for us was
is possible.
For decades, true software en- to prevent this adversary from being
cryp tion eluded computer scien- able to do this," Sahai says.
According to Sahai, his team's
tists. In 2001, seminal research by
Boaz Barak at the Weizmann Insti- research throws the doors open to
tute in Rehovot, Israel, and his col- new possibilities in the field of crypleagues proved that there are some
tography. In one possibility, called
programs for which an ideal ver- functional encryption, entire comsion of obfuscation is impossible. putable functions may be designed
This notion of obfuscation, called
to run differently for individual usvirtual black box, demands that an
ers depending on their identity or
encrypted program's inner work- purpose. For instance, a medical
researcher might have a unique key
ings be completely hidden. While
that allows access to sensitive hospidisappointing, this research still
held out the possibility that almost
tal data while keeping patients' perall programs could be encrypted us- sonal information private.
Sahai's team says the next step
ing another type of scheme, which
is called indistinguishability obfus- in their research is to reduce the
amount of computation needed to
cation, or IO. This type would also
perform obfuscation. Based on preobscure the program; however, the
source code could still, technically, vious trajectories in cryptographic
be deciphered if you were willing to
research, the system could be pracput in an impractical amount of time
tical in about a decade, Sahai says.
and resources.
Microsoft Research's Barak, for
"We didn't know if it was possible
one, extols the group's accomplishor not to achieve indistinguishabil- ment. "This new work...gives a proof
ity obfuscation" in 2001, says Barak, of concept that it could be achievnow a senior researcher at Microsoft
able," he says. "Even if it's not yet
Research New England.
practical...they showed how to use
What Sahai and his team-Sanjam
IO to achieve not all but many of the
Garg, Craig Gentry, Shai Halevi, and
applications of full-fledged obfuscaMariana Raykova of IBM Research, tion," he says.
and Brent Waters, an assistant
Shafi Goldwasser, a professor of
professor of computer science at
electrical engineering and computer
the University of Texas at Austin- science at MIT, says that while the
say they've proved with their math- team used a looser definition of obematical jigsaw puzzle trick is that fuscation than earlier research did,
indistinguishability obfuscation is
it's laudable that their system works
possible. Their research will be pre- on all programs under this new defisented this month at the 54th annual
nition. "It's clear that this is a hamIEEE Symposium on Foundations of
mer that works on a lot of nails; it
Computer Science, in Berkeley, Calif. can be used to address many other
Such obfuscation would be par- open problems of cryptography," she
says. "And from that point of view,
ticularly useful for software whose
inner workings could reveal security it's a big deal." -dav ey a lba

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Table of Contents for the Digital Edition of IEEE Spectrum October, 2013