References
W.R. Cheswick and S. M. Bellovin,
Firewalls and Internet Security
Addison-Wesley, 1994, ISBN 0-201-63357-4
S. Garfinkel,
PGP - Pretty Good Privacy
O'Reilly and Associates, 1995, ISBN 1-56592-098-8
Slide 71
©Copyright 1997
Jan Newmarch