Xiaoyun Wang Hongbo Yu Wei Wang Haina Zhang Tao Zhan Cryptanalysis on HMAC/NMAC-MD5 and MD5-MAC. 121-133 2009 EUROCRYPT http://dx.doi.org/10.1007/978-3-642-01001-9_7 conf/eurocrypt/2009 db/conf/eurocrypt/eurocrypt2009.html#WangYWZZ09