ABSTRACT
So far, we have introduced protections of communication systems placed at the
upper layers of networked communication systems. Those mechanisms utilize
modern cryptographic methods, together with network administration poli-
cies. The important characteristics of modern cryptographic algorithms and
protocols are that they are independent of physical-layer transmission tech-
nologies and assume that the physical-layer transmission has already been
established and is error free. For example, in order to provide security ser-
vices of encryption, authentication, data integrity, and digital signatures, we
have seen from the previous chapters, the core employed functions are cryp-
tographic (symmetric-key or public-key) algorithms. Examples include AES
(advanced encryption standard), SHA 1 (secure hash functions), RSA, Diffie-
Hellman (DH) key exchange protocol, digital signature standard (DSS), and
DH or DSS using elliptic curve public-key cryptographic algorithms.