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Crypto attack puts digital sig hash on collision course




Crypto attack puts digital sig hash on collision course
Crypto attack puts digital sig hash on collision course



http://www.theregister.co.uk/2009/06/10/digital_signature_weakness/ 

By Dan Goodin in San Francisco
The Register
10th June 2009 

Cryptographers have found new chinks in a widely-used digital-signature 
algorithm that have serious consequences for applications that sign 
email, validate websites, and carry out dozens of other online 
authentication functions.

The researchers, from Macquarie University in Sydney, Australia, found a 
way to break the SHA-1 algorithm in significantly fewer tries than 
previously required. Although the hash function was previously believed 
to withstand attempts numbering 2-63, the researchers have been able to 
whittle that down to 2-52, a number that puts practical attacks well 
within grasp of well-funded organizations.

Secure hashing algorithms are designed to reduce text or digital files 
to a unique series of letters and numbers that is often compared to the 
document's signature. The findings, which were published Wednesday here 
(PDF) [1], mean it's easier to create what cryptographers call 
collisions in SHA-1, in which two different sources share the same the 
same output.

"I'm expecting that we'll start seeing SHA-1 collisions before the end 
of the year, if not sooner," said Paul Kocher, president and chief 
scientist at Cryptography Research, a San Francisco-based consultancy. 
"For applications that fail because of collisions, you need to be really 
worried."

[1] http://eprint.iacr.org/2009/259.pdf 

[...]


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