The Office of the U.S. Secretary of Defense maintains a
reference site with a wealth of military and government security specifications. This site, the Specialized Command, Control, Communications, and Intelligence (C3I) Reference site, is available at
The Electronic Frontier Foundation (
) provides a great clearinghouse of privacy information at their Privacy Now! site (
). Most of the material there is focused on consumer- level privacy.
The Electronic Privacy Information Center (EPIC) has an
Web site and archive of privacy-
news, links, and resources. Check out
Rob Rosenberger maintains the
Vmyths site (
), which covers
, urban legends, and hype related to viruses. Major media in the United States routinely exaggerate the threat of virus and worm outbreaks.
Microsoft maintains its own virus information site at
Security Protocols and Algorithms
Protocol, n. A standard procedure for regulating data transmission between computers. Algorithm, n. A step-by-step problem-solving procedure,
an established, recursive computational procedure for solving a problem in a finite number of steps.
Why Do I Need to Know This?
Computer security involves a broad ”even bewildering ”array of concepts, some of which you might have seen for the first time in the
chapter. Apart from those conceptual underpinnings, if you want to effectively secure your Microsoft Exchange infrastructure, there s a separate set of security knowledge you need to be familiar with. That s because knowing which protocol or algorithm can best be used to strengthen a particular security weakness (as well as the flip side ” knowing which algorithms to avoid) is a key part of securing your computers. Just as a surgeon has to know the difference between a retractor and a hemostat, you need to know the difference between SHA-1 and SSL.
All of the algorithms and protocols covered in this chapter are widely used and well known. This might seem counterintuitive ”after all, doesn t security depend on keeping things hidden? It turns out that the answer is a resounding no. Depending on hiding the details of a security process or program, known derisively to experts as security through obscurity, never works in the long
. The famous cryptologist Auguste Kerckhoffs was the first to
this principle, which in general terms can be stated, The strength of a system cannot rely on the algorithm remaining unknown. Think of the trick puzzles you might have seen sold in catalogs: once you know the trick, it s trivial to solve the puzzle.
Let s say you have a secret document that you want to protect. If you hide it somewhere in your house, you re depending on obscurity to protect it, because
who stumbles across (or learns of) the hiding place has free access to the document. If you instead lock the document in a bank vault, that s security ”not just because the bank uses multiple
of security (including alarms, armed
, motion detectors, and the vault itself), but because the design of the vault has been studied and
by the American National Standards Institute (ANSI)
that specifies security measures for banks.
, validated algorithms and protocols is the best way to be secure, because these algorithms and protocols are the only ones that have undergone public (and probably private) scrutiny to ensure that they are as secure as their designers or
intended. If you were buying a safe to protect your life savings, you d want it to be a safe that met the banking industry s certification requirements, not a cheap unit that you picked up at your local discount store. With that said, you wouldn t choose a safe that cost more than you had in your life savings. As with all aspects of security, cost must be measured against benefits. Microsoft in general, and the Exchange team in particular, has done a good job of choosing Internet-standard protocols to provide security services, although you can augment those protocols with your own choice of hardware or software
This chapter is
a survey of three classes of information: security-
algorithms that are used to encrypt, authenticate, or
protect data; security protocols implemented or used by Exchange; and security services implemented or used by Exchange.
Because this isn t a book on cryptography, I m not including details of how these algorithms work. If you re interested, the Additional Reading section at the end of the chapter provides some good references.