[Infowarrior] - New attack against multiple encryption functions

[Richard Forno]

New attack against multiple encryption functions
New mathematical attack works against a broad range cryptographic  
functions.
Carl Jongsma 22/08/2008 10:01:00

http://www.computerworld.com.au/index.php/id;1395888957;fp;;fpid;;pf;1

Unless you're a dyed in the wool cryptographic geek you probably  
didn't know that there was a Crypto conference, or even a chain of  
worldwide crypto conferences that take place each year. Fortunately,  
for the most of us that aren't crypto geeks there are a handful of  
very highly skilled people who are; they can take the highly  
theoretical and complex mathematical proofs and arguments that make up  
most of modern cryptographic and cryptanalytic research and put it  
into plain language.

Probably the best known is Bruce Schneier, who is a dedicated crypto  
geek famous for his general Information Security and cryptographic  
work; including being responsible (or partly responsible) for ciphers  
such as Blowfish and Twofish. From his blog he has provided a  
tantalising suggestion that one of the most famous names in  
cryptography is introducing a new form of cryptanalysis.

Adi Shamir, who is the S in RSA, has presented material at the Crypto  
2008 conference that has promised a new form of mathematical attack  
against a broad range of cryptographic ciphers, including hash  
functions (such as MD5, SHA-256), stream ciphers (such as RC4), and  
block ciphers (such as DES, Triple-DES, AES). The new method of  
cryptanalysis has been called a "cube attack" and formed part of  
Shamir's invited presentation at Crypto 2008 - "How to solve it: New  
Techniques in Algebraic Cryptanalysis".

Comments from people who saw the presentation and had a chance to  
speak with Shamir (drawn from the comments in Schneier's blog)  
indicate that the new attack method isn't necessarily going to work  
against the exact ciphers listed above, but it presents a new generic  
attack method that can target basically formed ciphers irrespective of  
the basic cipher method in use, provided that it can be described in a  
"low-degree polynomial equation".

Without access to the paper (expected to be published later this  
year), the full scope of the discovery can't be easily determined. It  
may be that it delivers an order of magnitude improvement over  
existing methods, but implementation will still take such a long  
period of time that it is effectively impractical for attack against  
time sensitive content. Then again, it may be that it has brought it  
into a viable timeframe, something that can be achieved with a handful  
of modern machines - nothing that is too far out of reach of the  
motivated and resourced attacker.

What may be the biggest outcome from this research is the range of  
devices in widespread use that use weaker cryptographic protection,  
due to power or size limitations, that are now vulnerable to a  
straight forward mathematical attack. This might mean that some  
content delivery systems or simple communications channels are now  
vulnerable to a viable attack, or it could just form the basis of  
interesting class work for budding cryptographers and cryptanalysts.

Either way, it is something that will be worth watching over the next  
12-18 months to see how it evolves.