Following up on yesterday’s discussion about new attacks on cryptographic hashfunctions, Eric Rescorla points to a new paper 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.