Java 2 Network Security

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Java 2 Network Security
Some programs are better run on the client than on a server. So why couldn't
part of the content of the Web pages be executable? Why couldn't a page
comprise some text, some pictures, and some programs that run on the
client? There were two reasons:
1. It would be dangerous from a security point of view. There are enough
viruses on the Web anyway. With executable content, you might not even
realize that you were downloading potentially dangerous code.
2. The programs might not run on a particular operating system. One of the
joys of the Web was that you could choose whatever client system was
right for you and download pages running on a completely different
system.
But executable content, while potentially dangerous, is also extremely
valuable:
· Executable content can make a Web page much more exciting. This is
what Java became well known for in its early days: dancing cartoon
characters, bouncing heads, ticker tapes, etc. You can't do these if all the
programs must run on the server. Some of the early examples were
indeed just cute they showed what the technology could do, not why it
was important but appearance, excitement, and even cuteness are
important in attracting customers to a business site.
· Many dialogues with a customer are unbearably slow if you have to
communicate with a Web server at each interaction. With executable
content, the dialogue an insurance proposal, a request for a credit card,
a browse through a catalogue, or whatever can be completed on the
client machine, and the resulting transaction sent across the Web.
Java makes executable content possible while solving the problems noted
above by having three components:
1. A
Java Virtual Machine
(JVM) designed to prevent any code from
tampering with the client system. The code runs in a
protected space
, and
has only limited and always strictly controlled access to the surrounding
system. This is to meet Requirement 1 above. The arena of activity for any
specific code is defined by the client by way of a security policy. Java 2
provides an implementation for such protected spaces by the use of
protected domains, security policy files and security managers which we
shall see in greater detail in the later parts of this book.
2. A set of
bytecodes
JVM instructions which are interpreted by the JVM.
You are here: CodeIdol > Java > Java 2 Network Security > page: 25 26 27 28 29 30 31 32 33 34 35

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