Chun-Yuan Hsiao Leonid Reyzin Finding Collisions on a Public Road, or Do Secure Hash Functions Need Secret Coins? 92-105 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3152&spage=92 2004 conf/crypto/2004 CRYPTO db/conf/crypto/crypto2004.html#HsiaoR04