509 standard
describes the most
common format for
certi?¬?cates
46 The Problem
HTTP and HTTPS: The King Is Naked
Let??™s see how cryptography is applied by the most common
systems in use today; again, the reader who is already familiar
with HyperText Transfer Protocol (HTTP) and Secure Sockets
Layer (SSL) can safely skip this section.
The vast majority of users today access the Internet though a
browser. Internet Explorer and Firefox are two common examples.
Websites run on certain types of applications, called Web
servers, which sit in front of the ?¬?les that constitute the content
of the website itself. The job of the browser is to request a speci
?¬?c document of the Web server and render the document itself
once its bits have been received. The language in which
browser and Web server talk to each other is HTTP. It is a
simple, text-based protocol that was very easy to implement on
Trent Certificate
Authority
Trent
Bob
Alice
Bob
S
S
Figure 1-7 Alice, Bob, Trent and their relationships. Trent, on the top,
has his root certi?¬?cate signed his own private key; Bob has a certi?¬?cate
signed by Trent, containing Bob??™s public key; Alice can see both certi?¬?-
cates and hence acquire the associated public keys.
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