Sandeep S. Kumar Jorge Guajardo Roel Maes Geert Jan Schrijen Pim Tuyls The Butterfly PUF: Protecting IP on every FPGA. 67-70 2008 HOST http://dx.doi.org/10.1109/HST.2008.4559053 conf/host/2008 db/conf/host/host2008.html#KumarGMST08