Introduction - Contemporary Cryptography - page 3

and fingerprinting are currently very active areas of steganographic research
and development.

Figure 1.1 The relationship between cryptology, cryptography, cryptanalysis, and steganography.

The relationship between cryptology, cryptography, cryptanalysis, and stegano-
graphy is overviewed in Figure 1.1. In this topic, we address cryptography in a rather
narrow sense (this narrow sense is illustrated with a box in Figure 1.1). We elabo-
rate on cryptanalysis only where necessary and appropriate, and we do not address
steganography at all. There are many other topics that provide useful information
about steganography and steganographic technologies and techniques in general
(e.g., [3, 4]), and digital watermarking and digital fingerprinting in particular (e.g.,
[5, 6]).

1.2 CRYPTOGRAPHIC SYSTEMS

According to RFC 2828 [1], the term cryptographic system (or cryptosystem in
short) refers to “a set of cryptographic algorithms together with the key management
processes that support use of the algorithms in some application context.” Again, this
definition is fairly broad and comprises all kinds of cryptographic algorithms (and
protocols).
In some literature, the term cryptographic scheme is used to refer to a crypto-
graphic system. Unfortunately, it is seldom explained what the difference(s) between
a (cryptographic) scheme and a system really is (are). So for the purpose of this
topic, we don't make a distinction, and we use the term cryptographic system to
refer to either of them. We hope that this simplification is not too confusing. In the
realm of digital signatures, for example, people frequently talk about digital signa-
ture schemes. In this topic, however, we are talking about digital signature systems
and actually mean the same thing.