 Introduction
The expansion of the Internet and the Web has allowed more
people to have access to more and more information. At the same
time, the ability to keep information private has become an
important issue. Privacy is vital for businesses that want to
protect proprietary and other sensitive information, and for
individuals who engage in electronic commerce. Encryption is one
of the most effective tools for keeping information secure.
Cryptography has a long history, but until recently only the
government and the military were the users of cryptographic
systems. Today, many civil organizations and individuals are
using cryptography to protect information. There are several
reasons for this. First, the equipment for encryption/decryption
(i.e., powerful computers) has become more affordable. Second, an
increasing amount of information is stored on computers, changing
the way information is stored, transmitted and accessed in
society. Next, because of the complexity of communication
systems, users do not have complete control over the transmission
channels. This is why users are looking for tools that allow
secure communication over insecure channels. Finally,
cryptography as a science has received the attention of the
civilian sector, and important theoretical results and products
are now available to the public.
There are many security challenges in building safe
communication and collaboration. Typical security problems
include the following:
- Authentication:
 | How to know, when connecting to a site, who
operates the site? |
| How to perform authentication without sending the
user name and the password over the Internet? |
Eavesdropping:
| How to protect the privacy of a communication? |
| How to ensure that the messages have not been
modified between the sender and the receiver? |
| How to verify that the message received is an
identical copy of the original document? |
Authorization:
| How to ensure that the documents are read only by
the people who have the authorization to do so? |
The topic of Internet security is a very large one. Because
the Web operates at the highest level (application) in the OSI
model of communication networks, all the security problems in the
lower levels of the OSI model (data link, network, transport) are
potential sources of security risk in the Web too. For example,
the fact that the Internet's protocol (Domain Name System) to map
human-readable host names (e.g., cs.depaul.edu) into IP addresses
(e.g., 126.17.40.26) is insecure makes the Web system vulnerable
to the same attacks. The goal here is to present the basic
elements of cryptography used in achieving security in the
Internet in general, and in the Web in particular.
Rich Aliano
<raliano@shrike.depaul.edu>
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