Toru Akishita Tsuyoshi Takagi On the Optimal Parameter Choice for Elliptic Curve Cryptosystems Using Isogeny. 346-359 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2947&spage=346 2004 conf/pkc/2004 Public Key Cryptography db/conf/pkc/pkc2004.html#AkishitaT04