Donghoon Chang Jaechul Sung Seokhie Hong Sangjin Lee Improved Cryptanalysis of APOP-MD4 and NMAC-MD4 using New Differential Paths. 48 2008 2008 IACR Cryptology ePrint Archive http://eprint.iacr.org/2008/048 db/journals/iacr/iacr2008.html#ChangSHL08