Date Added: Jan 2012
In 2010, Tao Xie and Dengguo Feng [XF10] constructed the first single-block collision for MD5 consisting of two 64-byte messages that have the same MD5 hash. Details of their attack, developed using what they call an evolutionary approach, have not been disclosed "For security reasons". Instead they have posted a challenge to the cryptology community to find a new different single-block collision attack for MD5. This paper answers that challenge by presenting a single-block collision attack based on other message differences together with an example colliding message pair. The attack is based on a new collision finding algorithm that exploits the low number of bit-conditions in the first round.