For the first time, this book discloses our theoretical reasoning and practice details on hash function cryptanalysis as well as their implication in information security, mainly based on the collision attack on MD5 function as an example. A complete and easily understandable theory for the newly developed signed differential representation and weak input difference selection is given. A complete procedure of constructing differential collision paths is described. Almost all weak input differences which are possible to launch collision attacks are selected step by step in this book for MD5...