Hisayoshi Sato Tsuyoshi Takagi Satoru Tezuka Kazuo Takaragi Generalized Powering Functions and Their Application to Digital Signatures. 81-89 2006 89-A IEICE Transactions 1 http://dx.doi.org/10.1093/ietfec/e89-a.1.81 db/journals/ieicet/ieicet89a.html#SatoTTT06