[ISN] Flame's crypto attack may have needed $200, 000 worth of compute power

http://arstechnica.com/security/2012/06/flame-crypto-attack-may-have-needed-massive-compute-power/

By Dan Goodin
ars technica
June 11, 2012

The cryptographic attack that Flame engineers used to hijack Microsoft's 
Windows Update process was so computationally demanding, it would have 
required the equivalent of $200,000 worth of computing time from 
Amazon's EC2 Web service for most people to carry it out.

That estimate was delivered over the weekend at the SummerCon conference 
by Alex Sotirov, a co-founder and chief scientist of New York-based 
security firm Trail of Bits. One of seven researchers behind a 2008 
"collision" attack that generated an SSL certificate authority trusted 
by all major operating systems and browsers, Sotirov said the exploit 
required the equivalent of about $20,000 worth of computing time from 
EC2. The cost is because the precise window in which a fraudulent 
certificate could be constructed was just one second. That required him 
to try minting the certificate four times before he was successful. 
Rather than use the Amazon service, Sotirov's team used a cluster of 200 
PlayStation 3 consoles, which over a weekend delivered an equivalent 
amount of computing resources.

"Based on my analysis of Flame so far, the timing precision that they 
needed for Flame was one millisecond," Sotirov told Ars on Monday. 
"That's one-thousandth of a second, which is quite a bit more difficult 
to achieve than our work in 2008. Because of this timing issue, I'm 
speculating that the Flame authors had to try their attack many times, 
probably many more than the four I needed in 2008."

As Ars reported last week, the people designing Flame achieved 
mathematical breakthroughs that could only have been accomplished by 
world-class cryptographers. Specifically, the "chosen-prefix collision 
attack" was used to digitally sign malicious Flame components was an 
entirely new variant of the technique that researchers had never seen 
before. Sotirov said the $200,000 estimate is likely the maximum cost of 
the computing power that would have been required when Flame was likely 
being designed. He held out the possibility that the collision attack 
may have cost much less if the researchers figured out techniques that 
were less computing intensive.

[...]


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