Kemal Bicakci Nazife Baykal Design and Performance Evaluation of a Flexible and Efficient Server Assisted Signature Protocol. 1239-1244 http://csdl.computer.org/comp/proceedings/iscc/2003/1961/00/19611239abs.htm 2003 conf/iscc/2003 ISCC db/conf/iscc/iscc2003.html#BicakciB03