Toru Nakanishi Yuta Hira Nobuo Funabiki Forward-Secure Group Signatures from Pairings. 171-186 2009 Pairing http://dx.doi.org/10.1007/978-3-642-03298-1_12 conf/pairing/2009 db/conf/pairing/pairing2009.html#NakanishiHF09