NETGEAR CG814WG Router Manual PDF (Setup & Configuration Guide)

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Reference Manual for the Wireless Cable Modem Gateway CG814WG v2

D-6

Wireless Networking Basics

WEP Shared Key Authentication

This process is illustrated below.

Figure D-2:

802.11 shared key authentication

The following steps occur when two devices use Shared Key Authentication:

The station sends an authentication request to the access point.

The access point sends challenge text to the station.

The station uses its configured 64-bit or 128-bit default key to encrypt the challenge text, and

sends the encrypted text to the access point.

The access point decrypts the encrypted text using its configured WEP key that corresponds to

the station’s default key. The access point compares the decrypted text with the original

challenge text. If the decrypted text matches the original challenge text, then the access point

and the station share the same WEP key and the access point authenticates the station.

The station connects to the network.

If the decrypted text does not match the original challenge text (i.e., the access point and station do

not share the same WEP key), then the access point will refuse to authenticate the station and the

station will be unable to communicate with either the 802.11 network or Ethernet network.

FVM318

Access Point

1) Authentication

request sent to AP

2) AP sends challenge text

3) Client encrypts

challenge text and

sends it back to AP

4) AP decrypts,and if correct,

authenticates client

5) Client connects to network

802.11b Authentication

Shared Key Steps

Cable or

DLS modem

Client

attempting

to connect

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Reference Manual for the Wireless Cable Modem Gateway CG814WG v2

Wireless Networking Basics

D-7

Key Size and Configuration

The IEEE 802.11 standard supports two types of WEP encryption: 40-bit and 128-bit.

The 64-bit WEP data encryption method, allows for a five-character (40-bit) input. Additionally,

24 factory-set bits are added to the forty-bit input to generate a 64-bit encryption key. (The 24

factory-set bits are not user-configurable). This encryption key will be used to encrypt/decrypt all

data transmitted via the wireless interface. Some vendors refer to the 64-bit WEP data encryption

as 40-bit WEP data encryption since the user-configurable portion of the encryption key is 40 bits

wide.

The 128-bit WEP data encryption method consists of 104 user-configurable bits. Similar to the

40-bit WEP data encryption method, the remaining 24 bits are factory set and not user

configurable. Some vendors allow passphrases to be entered instead of the cryptic hexadecimal

characters to ease encryption key entry.

The 128-bit encryption is stronger than 40-bit encryption, but 128-bit encryption may not be

available outside of the United States due to U.S. export regulations.

When configured for 40-bit encryption, 802.11 products typically support up to four WEP keys.

Each 40-bit WEP Key is expressed as five sets of two hexadecimal digits (0-9 and A-F). For

example, “12 34 56 78 90” is a 40-bit WEP key.

When configured for 128-bit encryption, 802.11g products typically support four WEP keys but

some manufacturers support only one 128-bit key. The 128-bit WEP Key is expressed as 13 sets of

two hexadecimal digits (0-9 and A-F). For example, “12 34 56 78 90 AB CD EF 12 34 56 78 90”

is a 128-bit WEP key.

Typically, 802.11 access points can store up to four 128-bit WEP Keys but some 802.11 client

adapters can only store one. Therefore, make sure that your 802.11 access and client adapters

configurations match.

Whatever keys you enter for an access point, you must also enter the same keys for the client

adapter in the same order. In other words, WEP key 1 on the AP must match WEP key 1 on the

client adapter, WEP key 2 on the AP must match WEP key 2 on the client adapter, etc.

Note:

The access point and the client adapters can have different default WEP keys as long as the

keys are in the same order. In other words, the AP can use WEP key 2 as its default key to transmit

while a client adapter can use WEP key 3 as its default key to transmit. The two devices will

communicate as long as the access point’s WEP key 2 is the same as the client’s WEP key 2 and

the AP’s WEP key 3 is the same as the client’s WEP key 3.

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Reference Manual for the Wireless Cable Modem Gateway CG814WG v2

D-8

Wireless Networking Basics

How to Use WEP Parameters

Wired Equivalent Privacy (WEP) data encryption is used when the wireless devices are configured

to operate in Shared Key authentication mode. There are two shared key methods implemented in

most commercially available products, 64-bit and 128-bit WEP data encryption.

Before enabling WEP on an 802.11 network, you must first consider what type of encryption you

require and the key size you want to use. Typically, there are three WEP Encryption options

available for 802.11 products:

Do Not Use WEP:

The 802.11 network does not encrypt data. For authentication purposes, the

network uses Open System Authentication.

Use WEP for Encryption:

A transmitting 802.11 device encrypts the data portion of every

packet it sends using a configured WEP Key. The receiving 802.11g device decrypts the data using

the same WEP Key. For authentication purposes, the 802.11g network uses Open System

Authentication.

Use WEP for Authentication and Encryption:

A transmitting 802.11 device encrypts the data

portion of every packet it sends using a configured WEP Key. The receiving 802.11 device

decrypts the data using the same WEP Key. For authentication purposes, the 802.11 network uses

Shared Key Authentication.

Note:

Some 802.11 access points also support

Use WEP for Authentication Only

(Shared Key

Authentication without data encryption). However, the CG814WG v2 does not offer this option.

WPA Wireless Security

Wi-Fi Protected Access (WPA) is a specification of standards-based, interoperable security

enhancements that increase the level of data protection and access control for existing and future

wireless LAN systems.

The IEEE introduced the WEP as an optional security measure to secure 802.11g (Wi-Fi) WLANs,

but inherent weaknesses in the standard soon became obvious. In response to this situation, the

Wi-Fi Alliance announced a new security architecture in October 2002 that remedies the short

comings of WEP. This standard, formerly known as Safe Secure Network (SSN), is designed to

work with existing 802.11 products and offers forward compatibility with 802.11i, the new

wireless security architecture being defined in the IEEE.

WPA offers the following benefits:

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Reference Manual for the Wireless Cable Modem Gateway CG814WG v2

Wireless Networking Basics

D-9

•

Enhanced data privacy

•

Robust key management

•

Data origin authentication

•

Data integrity protection

Starting in August of 2003, all new Wi-Fi certified products had to support WPA and all existing

Wi-Fi certified products had one year to comply with the new standard or lose their Wi-Fi

certification. NETGEAR has implemented WPA on client and access point products. As of August

2004, all Wi-Fi certified products must support WPA.

How Does WPA Compare to WEP?

WEP is a data encryption method and is not intended as a user authentication mechanism. WPA

user authentication is implemented using 802.1x and the Extensible Authentication Protocol

(EAP). Support for 802.1x authentication is required in WPA. In the 802.11 standard, 802.1x

authentication was optional. For details on EAP specifically, refer to IETF's RFC 2284.

With 802.11 WEP, all access points and client wireless adapters on a particular wireless LAN must

use the same encryption key. A major problem with the 802.11 standard is that the keys are

cumbersome to change. If you don't update the WEP keys often, an unauthorized person with a

sniffing tool can monitor your network for less than a day and decode the encrypted messages.

Products based on the 802.11 standard alone offer system administrators no effective method to

update the keys.

For 802.11, WEP encryption is optional. For WPA, encryption using Temporal Key Integrity

Protocol (TKIP) is required. TKIP replaces WEP with a new encryption algorithm that is stronger

than the WEP algorithm, but that uses the calculation facilities present on existing wireless devices

to perform encryption operations. TKIP provides important data encryption enhancements

including a per-packet key mixing function, a message integrity check (MIC) named Michael, an

extended initialization vector (IV) with sequencing rules, and a re-keying mechanism. Through

these enhancements, TKIP addresses all of known WEP vulnerabilities.

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Reference Manual for the Wireless Cable Modem Gateway CG814WG v2

D-10

Wireless Networking Basics

How Does WPA Compare to IEEE 802.11i?

WPA is forward compatible with the IEEE 802.11i security specification currently under

development. WPA is a subset of the current 802.11i draft and uses certain pieces of the 802.11i

draft that were ready to bring to market in 2003, such as 802.1x and TKIP. The main pieces of the

802.11i draft that are not included in WPA are secure IBSS (Ad-Hoc mode), secure fast handoff

(for specialized 802.11 VoIP phones), as well as enhanced encryption protocols such as

AES-CCMP. These features are either not yet ready for market or will require hardware upgrades

to implement.

What are the Key Features of WPA Security?

The following security features are included in the WPA standard:

•

WPA Authentication

•

WPA Encryption Key Management

–

Temporal Key Integrity Protocol (TKIP)

–

Michael message integrity code

(MIC)

–

AES Support

•

Support for a Mixture of WPA and WEP Wireless Clients

These features are discussed below.

WPA addresses most of the known WEP vulnerabilities and is primarily intended for wireless

infrastructure networks as found in the enterprise. This infrastructure includes stations, access

points, and authentication servers (typically RADIUS servers). The RADIUS server holds (or has

access to) user credentials (e.g., user names and passwords) and authenticates wireless users

before they gain access to the network.

The strength WPA comes from an integrated sequence of operations that encompass 802.1X/EAP

authentication and sophisticated key management and encryption techniques. Its major operations

include:

•

Network security capability determination.

This occurs at the 802.11 level and is

communicated through WPA information elements in Beacon, Probe Response, and (Re)

Association Requests. Information in these elements includes the authentication method

(802.1X or Pre-shared key) and the preferred cipher suite (WEP, TKIP, or AES).

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