Book excerpt: A practical guide to Cryptography and its use in the Internet and other communication networks. This overview takes the reader through basic issues and on to more advanced concepts, to cover all levels of interest. Coverage includes all key mathematical concepts, standardisation, authentication, elliptic curve cryptography, and algorithm modes and protocols (including SSL, TLS, IPSec, SMIME, & PGP protocols). * Details what the risks on the internet are and how cryptography can help * Includes a chapter on interception which is unique amongst competing books in this field * Explains Public Key Infrastructures (PKIs) - currently the most important issue when using cryptography in a large organisation * Includes up-to-date referencing of people, organisations, books and Web sites and the latest information about recent acts and standards affecting encryption practice * Tackles the practical issues such as the difference between SSL and IPSec, which companies are active on the market and where to get further information