文档介绍：Appendix A
Cryptography Primer:
Introduction to Cryptographic
Principles and Algorithms
Panayiotis Kotzanikolaou and Christos Douligeris
INTRODUCTION
As the term itself manifests, the original purpose of cryptography is message confi dential-
Modern cryptography, however, spans a wider range of topics. Formally speaking,
“cryptography is the study of mathematical techniques related to aspects of information
security such as confi dentiality, data integrity, authentication and non-repudiation”[1].
This defi nition requires the defi nition of the basic security aspects of information
security.
Confi dentiality is the property of protecting the content of information from all users
other than the ones intended by the legal owner of the information. The nonintended users
are generally called unauthorized users. Other terms such as privacy or secrecy have been
used almost synonymously with confi dentiality. Data integrity is the property of protecting
information from alteration by unauthorized users. Authentication is divided into entity
authentication and data authentication. Entity authentication is the property of ensuring
the identity of an entity, which may be a human, machine, or other asset. Data origin
authentication is the property of ensuring the source of the information. Finally, nonrepu-
diation is the property of ensuring that entities that mitted to an action cannot
deny mitment at a latter time.
Apart from the above basic security objectives, cryptography may assist in achieving
several other security objectives of information systems, such as access control, anonym-
ity, and timestamping. However, although cryptography is an essential element work
and systems security, it must be clear that cryptography by itself is not a synonym of
security. In almost every information system work, procedural measures, organi-
zational techniques, and additional technical means are generally requ