Sarvar Patel Zulfikar Ramzan Ganapathy S. Sundaram Luby-Rackoff Ciphers: Why XOR Is Not So Exclusive. 271-290 2002 conf/sacrypt/2002 Selected Areas in Cryptography http://link.springer.de/link/service/series/0558/bibs/2595/25950271.htm db/conf/sacrypt/sacrypt2002.html#PatelRS02