Introduction - Contemporary Cryptography - page 2

(i.e., to hide its semantic content), prevent its undetected alteration, or pre-
vent its unauthorized use. If the transformation is reversible, cryptography
also deals with restoring encrypted data to intelligible form.” Consequently,
cryptography refers to the process of protecting data in a very broad sense.

• The term cryptanalysis is derived from the Greek words “kryptos” (see

above) and “analyein,” standing for “to loosen.” Consequently, the meaning
of the term can be paraphrased as “loosen the hidden word.” This paraphrase
refers to the process of destroying the cryptographic protection, or—more
generally—to study the security properties and possibilities to break cryp-
tographic techniques and systems. Again referring to RFC 2828 [1], the term
cryptanalysis is used to refer to the “mathematical science that deals with
analysis of a cryptographic system in order to gain knowledge needed to break
or circumvent the protection that the system is designed to provide.” As such,
the cryptanalyst is the antagonist of the cryptographer, meaning that his or
her job is to break or at least circumvent the protection the cryptographer has
designed and implemented in the first place.

Many other definitions for the terms cryptology, cryptography, and cryptanaly-
sis are available and can be found in the relevant literature (or on the Internet, respec-
tively). For example, the term cryptography is sometimes said to refer to the study
of mathematical techniques related to all aspects of information security (e.g., [2]).
These aspects include (but are not restricted to) data confidentiality, data integrity,
entity authentication, data origin authentication, and/or nonrepudiation. Again, this
definition is very broad and comprises anything that is directly or indirectly related
to information security.
In some literature, the term cryptology is even said to include steganography
(in addition to cryptography and cryptanalysis).

• The term steganography is derived from the Greek words “steganos,” standing

for “impenetrable,” and “graphein (see above). Consequently, the meaning of
the term is best paraphrased as “impenetrable writing.” According to Request
for Comments (RFC) 2828 [1], the term steganography refers to “methods
of hiding the existence of a message or other data. This is different than
cryptography, which hides the meaning of a message but does not hide
the message itself.” An example of a formerly used steganographic method
is invisible ink. Contemporary methods are more sophisticated and try to
hide additional information in electronic files. In general, this information is
arbitrary. It may, however, also be used to name the owner of a file or the
recipient thereof. In the first case, one refers to digital watermarking , whereas
in the second case one refers to digital fingerprinting . Digital watermarking