Kapali Viswanathan Ashutosh Saxena Towards Logically and Physically Secure Public-Key Infrastructures. 122-134 2002 conf/indocrypt/2002 INDOCRYPT http://link.springer.de/link/service/series/0558/bibs/2551/25510122.htm db/conf/indocrypt/indocrypt2002.html#ViswanathanS02