Single Sockets Layer (SSL) is the protocol developed by openly cooperating engineers at Netscape Communications and interested Web citizens in the early part of the 1990s. Slightly adapted and renamed TLS (Transport Layer Security), it lives on in its latest incarnation with a view to providing secure, reliable communications for users of electronic commerce--both vendors and customers. This brief book outlines the reasons for the development of SSL, its philosophy of operation and plenty of interesting particulars about its implementation. The style is straightforward and will be understandable by those with little more than a nodding acquaintance with computer networking or the Internet. The terse but useful introduction to cryptography and certificate authorities sets the stage, while subsequent chapters wade deeper into the subjects such as details of message exchanges within Microsoft Server Gated Cryptography. There is a long explication of X.509 Digital Certificates which, while useful in the context of security, seems out of place when the objective of the book is to introduce SSL. A CD-ROM version of the text is bound in at the back cover. Well illustrated (especially the introduction to cryptography) and supplemented with lots of charts and tables, SSL and TLS Essentials serves as a non-technical summary of SSL with just enough detail to whet the appetite of would-be engineers, plus an excellent follow-on bibliography for those wishing to pursue the subject further.--Wilf Hey