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.