SHA-0 Broken, MD5 Rumored Broken

["Jérôme" ATHIAS <jerome.athias () caramail com>]

MD5 Collision Nearly Found

Following up on yesterday's discussion about new attacks on cryptographic hashfunctions, Eric Rescorla points to a new 
paper (http://eprint.iacr.org/2004/199.pdf) from Chinese computer scientists, which claims to have found a collision in 
MD5. MD5 is a cousin of the SHA-1 function discussed yesterday; MD5 is believed to be the weaker of the two.

The paper is odd, in that it includes two values that it claims have the same MD5 value, but it doesn't explain how the 
claimed collision was generated. And it turns out that the authors made an error, so that the two values don't in fact 
generate the same MD5 value. Eric and the commenters on his site did some clever detective work to determine that the 
two published values generate a collision for a slightly different function, which Eric dubbed MD5'. MD5' is very 
similar to MD5 so it seems very likely that the new attack can be extended to the real MD5.

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