Cisco 1231G - Aironet - Wireless Access Point Specifikace stáhnout pdf (Strana 120)

Chapter 4 Security Setup

Security Overview

4-8

Cisco Aironet 1200 Series Access Point Software Configuration Guide

OL-2159-01

During shared key authentication, the access point sends an unencrypted

challenge text string to any device attempting to communicate with the access

point. The device requesting authentication encrypts the challenge text and

sends it back to the access point. If the challenge text is encrypted correctly,

the access point allows the requesting device to authenticate. Both the

unencrypted challenge and the encrypted challenge can be monitored,

however, which leaves the access point open to attack from an intruder who

calculates the WEP key by comparing the unencrypted and encrypted text

strings. Because of this weakness, shared key authentication can be less

secure than open authentication. Like open authentication, shared key

authentication does not rely on a RADIUS server on your network.

Figure 4-5 shows the authentication sequence between a device trying to

authenticate and an access point using shared key authentication. In this

example the device’s WEP key matches the access point’s key, so it can

authenticate and communicate.

Figure 4-5 Sequence for Shared Key Authentication

Protecting the Access Point Configuration with User Manager

The access point’s user manager feature prevents unauthorized entry to the access

point management system. You create a list of administrators authorized to view

and adjust the access point settings; unauthorized users are locked out. See the

“Setting Up Administrator Authorization” section on page 4-38 for instructions

on using the user manager.

Access point

or bridge

with WEP key = 123

Client device

with WEP key = 123

1. Authentication request

2. Unencrypted challenge

3. Encrypted challenge response

4. Authentication response

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Cisco 1231G - Aironet - Wireless Access Point Specifikace Strana 120