Elena Andreeva Charles Bouillaguet Orr Dunkelman John Kelsey Herding, Second Preimage and Trojan Message Attacks beyond Merkle-Damgård. 393-414 2009 Selected Areas in Cryptography http://dx.doi.org/10.1007/978-3-642-05445-7_25 conf/sacrypt/2009 db/conf/sacrypt/sacrypt2009.html#AndreevaBDK09