Security on Wireless Communications

INTRODUCTION


Mobile satellite communications have been implemented for many
systems, including maritime, aeronautical, and land systems. A
main characteristic of mobile satellite communication systems
is that they provide wireless access to traditional wireline
networks for a large number of access services, such as
telephone calls. But wireless transmission is vulnerable to
relatively easy interception, such as fraudulent call attempts
and intrusion or listening-in by third parties. Thus, we action
must be taken to prevent various kinds of intrusion. For
example, sensitive data must be protected against disclosure
to an unauthorized person. Fraudulent modification of messages,
repeating old messages, or one user masquerading as another
must also be prevented. Data are particularly vulnerable when
transferred in networks, especially in mobile communication
networks. For this reason, a feasible solution for
implementation of secure mobile communication systems is needed.

A simple but effective method for secure digital communications
is the use of encryption methods. Two types of encryption
methods are available: private-key cryptosystems, such as DES
and FEAL-32, and public-key cryptosystems, such as RSA. In
public-key cryptosystems the degree of computational complexity
increases with the level of security. As a result, public-key
cryptosystem cannot be used in low-cost and low-power mobile
(portable) communication systems, because no existing protocol
provides acceptable call-setup time performance. Private-key
cryptosystems are simpler and faster than public-key cryptosystem
as far as computational complexity is concerned. But private-key
cryptosystems require a tremendous amount of effort for key
management and distribution. Private-key cryptosystems require
that parties (portable) to the conversation share knowledge of
a secret key and that unauthorized users not have access to this
key. Key agreement is the process by which the parties agree
upon the proper key.

In this peport, we propose a new service for digital mobile
communication systems. This service enables two or more users to
hold a secure electronic conference. Two requirements must be
considered: privacy and authentication. Privacy involves ensuring
an eavesdropper cannot intercept conversations during a conference
or information about conferees' locations. Authentication involves
ensuring that service is not obtained fraudulently in order to
avoid charges for usage. We thus have the following four security
goals for the mobile communication system:

 1. Privacy of conversation content during the conference.
 2. Privacy of information about conferees' locations during the
    conference.
 3. Prevention of fraud by ensuring that the portable units are
    authentic.
 4. Prevention of replaying attacks, so that intruders are not
    able to obtain sensitive data by replaying a previously
    intercepted message.


Since the portable units must operate over long periods of time
on small, low-power batteries, low complexity implementation of
the encryption function is critical. Private-key cryptosystems
meet such criteria. As mentioned above, private-key cryptosystems
require a session key agreed upon by the conferees in the
conference.