Cryptography Reference
In-Depth Information
Chapter 7
Practical Applications
So far in this topic, we have learned a number of algorithms and discussed
problems in their implementation. In the previous chapter, we looked at cryp-
tographic protocols as a theoretical basis of their application, so to speak. In
this chapter, we will go a step forward, discussing the actual use, in this case,
of cryptographic programs. As before, we are interested mainly in understand-
ing the background rather than trying to achieve completeness. This is why we
will be dealing with only a few free programs in this chapter. The source texts
of all of these programs can be found on the Internet and on our web site.
Also, you shouldn't expect operating instructions for these programs in the
following. There is plenty of documentation out there, and piles of topics, espe-
cially on PGP (I recommend [GarPGP]). What these topics and documents don't
discuss extensively, though, are cryptological implementation details. This is
what you will find in this chapter. For this reason, it doesn't really matter
that some of the programs, or the protocols used, discussed in this chapter are
outdated. The important thing is to understand the principles.
7.1 PGP—A King Among Cryptographic Programs
You've probably heard of the free program PGP (Pretty Good Privacy). I don't
know of any other software that has stirred up so much dust, and that has
apparently been a thorn in the flesh of so many national intelligence agencies.
