The Promise and Perils of a Ubiquitous

Wireless Internet

Steven Esposito∗ Geoffrey Jacoby† Peter White‡

October 29, 2003

∗steven.esposito@duke.edu†geoffrey.jacoby@duke.edu‡peter.white@duke.edu

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Wireless Internet service shows great promise in allowing users to have

nation-wide, ubiquitous Internet access. Two varieties of service are forming.

In one variety, a user is given free wireless access either as advertising or as

a public service. In another, the user pays for wireless access from a com-

mercial provider, must like a wired ISP. However, the very nature of wireless

creates some additional technical problems which wired connections do not

have to consider. Because wireless connections use collision avoidance rather

than collision detection, wireless connections have additional overhead. In

addition, because wireless connections use RF signals rather than hard-to-

tap wire, they are vulnerable to eavesdropping. Also, wireless connections

are susceptible to freeloading if proper authentication is not implemented.

The current security protocol,WEP, is fatally flawed due to improper imple-

mentation and use of a weak key. Before commercial services can mature,

these problems with authentication and security must be satisfactorily dealt

with.

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1 Introduction

At the moment, consumers are faced with the choice between mobility and

broadband. There exist national dial-up ISPs, such as Earthlink and AOL,

which offer local numbers in most areas to their subscribers. However, these

dial-up connections operate at at most 56 kbps, the maximum speed of a mo-

dem. Likewise, there exist broadband providers, who, through cable modems

or DSL, can provide broadband connections to a fixed location. These con-

nections, while still not as fast as a direct connection such as a T1 line, still

offer far more bandwidth than dial-up. However, broadband is not portable.

In recent years, wireless access using a base station, which also acts as a

NAT, has become a popular way for broadband users to extend their cable

or DSL service to their entire house, rather than merely one computer. This

concept is beginning to be extended to the creation of ISPs, both non-profit

and commercial, which are purely wireless. In theory, wireless connections

offer more bandwidth than even broadband, with a cheaper infrastructure

and easier upgradability. Thus, they are a better solution than the last mile

problem than cable or DSL. However, there are issues of security and authen-

tication which must be dealt with before wireless ISPs can become mature

and fulfill their great potential.

In this paper, we will survey some examples of existing wireless service,

and how they are dealing with the issues of authentication, service cover-

age, and security. Second, we will show the nature and flaws of the existing

3

wireless security protocol WEP, and how VPN can be used to provide au-

thentication. Lastly, we will describe some current attempts to replace WEP

with better protocols..

2 Types of Service

There are two different major types of wireless service that will soon be

available in most of the United States. While variations exist of both, the

security requirements change little from variation to variation. In the first

type, the subscription model, a consumer directly pays an ISP to receive

wireless service. In the second type, the free model, the provider allows

wireless access for free, subsidizing it by different means.

2.1 Free Model

Under this method of service, the consumer does not directly bear the cost

of his own access. The access is either subsidized by a company to attract

customers, by the government for its citizens, or by individuals to provide

access to their own neighborhood. For free model providers, authentication

is much less important than security and service coverage. After all, the

purpose of most free model networks is to provide access to whomever is in

the area and wishes to use the Internet. Since there is no billing, there might

not be a need to verify who is using the system. Therefore, authentication

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can often, but not always, be left to the application layer.

The security of the individual computers, as well as the security of the

transmissions themselves, remains vitally important. Even users in a coffee

shop will still hesitate to use wireless connections for, say, instant messaging,

if a user at another table can eavesdrop easily.

However, the main problem which free models must grapple with is service

coverage. Aside from a state funded nation-wide or state-wide network, all

free models are hampered by their limited range. For most free providers,

this is not a problem. In fact, for those who will use wireless access as a

lure to attract customers to come to their place of business, this limited

range is in fact a feature for them. From the user’s point of view, however,

wireless networks based entirely on free models will likely be patchy. Without

the hope of income or a profit motive to invest in such an infrastructure, it

is unlikely that complete coverage can be achieved, even with community

organization.

Nevertheless, free models can provide advertising for a business, or a ser-

vice to a community. Free Internet could be a great boon for poorer neigh-

borhoods or communities, while at the same time helping to spur adoption of

wireless technologies, which would also help subscription ISPs. Two major

types of the Free Model exist at the moment-community wireless LANs such

as NYCWireless, and universities such as Duke.

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2.2 Examples of the Free Model

2.2.1 Duke University

Duke University is a private university based in Durham, NC. Through its

Office of Information Technology, it has in recent years begun an aggressive

campaign to provide wireless access to most social and classroom spaces.

Currently, about 41 buildings, mostly classrooms and libraries, have wire-

less. Authentication is handled by refusing access to MAC addresses unreg-

istered with the university. Since the wireless network is designed to serve

the University community, which relatively stable, this system works fairly

well for students and faculty. It is unfortunate, however, that because of this

authentication method, visitors are not easily able to use wireless.

WEP is not used. However, as all official online University functions, such

as registrar and bursar accounts, are accessed using password authentication

over SSL, WEP is not needed [1].

2.2.2 NYCWireless

NYCWireless is a non-profit organization which seeks to foster grassroots

wireless networks in the New York area. It supports 802.11b. Access is

entirely free, and no authentication, even a password, is required. WEP

is not used, for technical reasons described later.[2] Therefore, any security

must come at the application layer, such as ssh, SSL, or VPN. This is not,

however, a major liability for a public wireless network. A public wireless

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network is, by design, meant to allow as many people as possible to connect,

not to exclude users. The option for businesses to use their own VPN systems

allows for security without inconveniencing those who do not need encrypted

transmissions.

2.3 Subscription Model

The subscription model uses essentially the same business plan as traditional

wired ISPs. The service, Internet access, is the same. Only the medium of

transmission changes. However, the nature of wireless transmissions creates

complications in both service coverage and security, just as in free networks.

In addition, authenticating who may and who may not be granted access to

the network’s bandwidth becomes a key concern.

Because of the limited range of wireless base stations, multiple stations

might be necessary to cover a building. Whereas Ethernet may be at most

2500m in length, a wireless base station typically covers only a few hundred

feet.[3] For example, Apple markets its Airport Base Station, which uses the

802.11b standard, as having a range of 150 feet [4]. This is mitigated, how-

ever, by the relative cheapness of base stations. Also, one of the advantages

of wireless networks is that they are modular. One need only provide as

much infrastructure as one requires at the time, and if more is needed later,

it can be added. In contrast, to install cable to a neighborhood, one must do

so all at once, as the cost of digging repeatedly to lay cable is prohibitive.

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In addition, upgrading wired networks such as cable or DSL lines often

must be done all at once, as it involves costly digging. Upgrading the ca-

pabilities of a wireless network can be done either by replacing inexpensive

commodity hardware, or via a firmware upgrade. Several of the 802.11 proto-

cols use the same 2.4 GHz spectrum, and so upgraded WAPs are backwards

compatible with their less capable predecessors. It is also possible to build

a WAP which can transmit on multiple protocols. This backwards com-

patibility is especially important with heterogenous coverage. Most current

subscription models foresee using networks of smaller ISPs. Not all access

points, therefore, will use the same version or brand of equipment, because

not all ISPs will have the funds to buy the most modern equipment.

In addition, because of the mobile nature of wireless access, customers

will be moving from provider to provider as they travel, even within a few

city blocks. Some of these providers will undoubtedly be either from a rival

ISP, or from a free provider. Keeping all WAPs compatible with 802.11b will

ensure that the user will not have to worry about which protocol to use.

2.4 Examples of the Subscription Model

2.4.1 Boingo

Sky Dayton, the founder of Earthlink, has created a wireless ISP known as

Boingo. The theory behind the service is similar to that of Earthlink. Much

as Earthlink achieved nationwide dial-up coverage by making alliances with

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smaller, local ISPs, so Boingo is attempting to provide a nation-wide wireless

service by fostering the creation of local wireless hotspots.

For $799, a business may buy a WAP which provides access for Boingo

customers, and can be used to provide service for non-Boingo customers as

well. [5]. Through a revenue sharing arrangement, the business receives $1 for

each user who pays to connect through that WAP, plus $20.00 for each new

user the business recruits for Boingo. Users pay from $7.95 for one-time use

to $50.00 for unlimited national use, and are supplied with client software

from Boingo which, according to Boingo, sniffs out WAPs and takes care

of connection details transparently.[6] Having a nation-wide provider helps

to solve the problem of authentication-only one authentication is needed to

connect anywhere. In addition, VPN is available for security for an added

fee.

This system is designed to encourage small, independent ”HotSpots” to

do the work of building a nation-wide network for Boingo, and to pay for

the privilege in the hopes of eventual profit. At the same time, Boingo also

is focusing its attention on places well-traveled by business people who need

constant access to email and the Internet. Examples of this include hotels,

airports, and convention centers [7].

So far, however, Boingo has yet to meet its goals. Its coverage, even in

major metropolitan areas, is fairly sparse [8]. Its price for monthly, national

access is higher than many broadband cable and DSL packages, while at the

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same time its one-time use fee, $7.95, seems quite steep. Should enough ISPs

sign on to the Boingo plan, the service has the potential to reach its goals.

However, if this does not happen soon, it might not happen at all. This

is because of a new venture recently announced by AT&T, IBM, and Intel

called Cometa.

2.4.2 Cometa

Details on Cometa are so far quite scarce. However, some preliminary infor-

mation about the endeavor has been released. AT&T will be providing the

infrastructure, with IBM ”handling wireless site installations and back-office

systems” [9]. Like Boingo, Cometa would allow users to use one sign-on

procedure for any Cometa wireless hotspot in the country. Unlike Boingo,

however, Cometa has only announced plans to deal with telecommunications

companies and ISPs, not individual users.

Cometa’s goals are quite lofty. Support for both 802.11b and 802.11a is

planned. It hopes to add 20,000 WAPs, so that by 2004 there will be nearby

coverage-within five minutes travel-of most users in major metropolitan areas

in the United States..

Cometa has not yet announced what technologies it will be using for

authentication or security. Both will be key to its success or failure, as

broken authentication will allow consumers to use the service without paying,

and broken security will make businesses reluctant to use the service. [9] In

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particular, it is important that they not rely upon WEP for effective security.

3 The Wireless Protocol: 802.11, and why

WEP is not effective

Before 802.11, each company or ISP network was a WAN that ran on cables

behind walls and linking to each other and the external internet at a rack

of switches behind a locked closet door. 802.11 introduced the ability for

network traffic to be carried over radio waves so that people would not be

restricted by wires. Unfortunately, by moving it outside the walls and locked

cabinets, it became much easier for people to secretly listen in to all WAN

traffic, or at least the components going back and forth between wireless

clients.

The IETF 802.11 standard describes the use of radio transmission of

ethernet packet data for LAN’s and WAN’s. It outlines the transmission

of packet data between Wireless Access Points (WAP’s) and users across

unrestricted frequencies. It also optimizes support for ad hoc connectivity,

users switching connections between WAP’s, and users not being able to

detect all the other users sharing the WAP. 802.11 also outlined a security

and authentication scheme based on secret key encryption called the Wired

Equivalent Protocol (WEP). While the transmission standards of 802.11 were

a raging success, WEP turned out to be rather easy to crack, forcing other

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authentication and security methods to be used, methods which were not as

scalable as WEP would have been

3.1 CSMA/CA: How different users can use a WAP

without colliding

The IETF wireless protocol is mostly interested in treating wireless connec-

tions like wired connections. Since Wireless users and WAPs are not actu-

ally connected physically, there are many different orientations that different

senders and receivers (and different signal strenghts) can be in relation to

each other. This means that two users might be in range of a WAP, but not

in range with each other. Thus, if they both tried to communicate at the

same time, the collision would only be detected at the WAP. So, collision

detection would be impossible without some sort of strict orientation.

In addition, wireless hardware is only half duplex,[10] because receiving

and sending at the same time from two different antennae in the space of a

PCMCIA card is relatively impossible. Thus, wireless radios are not able to

detect someone else transmitting if they are transmitting.

Therefore, The wireless protocol uses a collision avoidence scheme that

equates to each wireless object asking permission and listening for acknowl-

edgement before sending a packet. This creates much more overhead and

permission/acknowledgement packets being sent

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3.2 802.11... Which standard is right for you?

802.11a and 802.11b are the two main wireless standards. 802.11b is the most

prolific, but 802.11a has more bandwidth capacity. They are also in com-

pletely different bands of the radio spectrum (802.11a being at 5GHz, and

802.11b transmitting at 2.4 GHz) and use different methods to span data

across channels of those bands (802.11a uses Orthogonal Frequency Divi-

sion Multiplexing OFDM, and 802.11b uses direct sequence spread spectrum

modulation). Thus, they cannot interoperate without completely different

hardware at the link state.

Jim Grier describes the perks of the two different options as follows [11]:

1. 802.11b - More prevalent and therefore cheaper to get infrastructure

for. It has broadcast ranges of about 300 feet from a base station, and

averages about 5 MBits per second.

2. 802.11a - Newer, but also carries 5 times the bandwidth. This is use-

ful for applications that create much more network traffic (streaming

video, x-tunneling). Unfortunately, it cycles much faster and has more

complex data storage, so it can only transmit about 60 feet from a base

station.

Grier[11] also points out that there are more WAPS coming out that

operate with both standards, allowing both protocols to be used within the

same network.

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3.3 WEP: It was such a good idea

WEP (Wired Equivalent Protocol) is the IETF wireless security protocol

that was concocted to handle three things in link state [12]:

1. Access Control - Allow only those with the correct key the ability to

communicate effectively with the WAP

2. Data Integrity - Make sure that wireless datagrams cannot be inter-

cepted, modified, and passed on undetected.

3. Confidentiality - Prevent casual eavesdropping of wireless traffic going

across the network.

These would all be done transparently at link state, requiring only the

input of a WEP key by the user. Using this, all packets going between

sers and a WAP would be secure, authentic, and not tampered with. This

standard was created with the knowledge that it would be much easier for an

attacker to be able to access network traffic because it was being transmitted

openly in various high gigahertz ranges.

A summary of the encryption scheme seen in [12] is as follows:

1. Checksum - Use this to check the packet for data integrity, and con-

catenate the checksum onto the packet.

2. Encrypt - The checksum and packet combination using an RC4 gener-

ated keystream: to do this, generate a keystream (a sequence of pesudo-

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random bytes) using the RC4 stream cypher algorithm given the secret

key and an initialization vector (IV) value. Then, x-or the keystream

to the checksum/packet. The result is encrypted data with a key cal-

culated by the combination.

3. Transmit - Transfer the encrypted data and the IV value to a receiver.

Using the known WEP key and the transmitted IV value, the receiver can

create the same keystream used for encryption and decrypt the message

and checksum. The receiver can then check the integrity of the message by

rehashing it to see if it matches the checksum.

Classic WEP does the above procedure using 40 bit keys, there is also an

extended wep that uses stronger (longer) keys and initialization vectors which

are utilized by sepecific vendors of wireless hardware (part of the difference

between Orinoco GOLD and SILVER systems is the use of longer wep keys

in GOLD)

Thus the three above goals are satisfied. Each message going back and

forth between the WAP and a user would be encrypted using the WEP key,

so casual eavesdropping would be made difficult without using a brute force

approach to find the key. Also, only users who know the key would be able to

send sensible packets to the WAP, so it serves as authentication by knowing

the key. Finally, the checksum encrypted along with the message makes

ensures integrity.

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3.4 WEP: It was such a bad implementation

While WEP was hopeful, and had taken into accound the fact that commu-

nications could be much more easily intercepted, it turned out to be a rather

bad scheme in practice. Borisov et al. [13] showed how each of WEP is

insufficient in meeting its three goals of confidentiality, authentication, and

integrity.

The first fault of the IETF was thinking that attacks would be imprac-

tical despite the fact that messages could be easily interceptable. However,

since more and more 802.11 equiptment is being set up for various reasons,

antennae and connection equiptment for wireless hardware has been getting

cheaper. We managed to obtain a new 9 dB gain 2.4 gigahertz antenna and

the pigtail to connect to an Orinoco card for about sixty dollars. This an-

tenna could pick up traffic from normally broadcasting WAP’s about a mile

away (it picked up WAPs in biddle from the Bryan Center parking lot). More

sophisticated equiptment could be bought by the serious corporate spy easily

(check prices at http://www.hyperlinktech.com).

This means that the assumption that it would be rather hard to intercept

significant portions of wireless traffic is incorrect. It is entirely feasable to

have someone reading and analyzing traffic undetected from rather far away.

This would not be a problem if the encryption scheme was so strong that

unlimited scanning of wireless traffic would not yeild an easier way to crack

the scheme.

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Unfortunately, as Borisov et al. [13] shows, WEP is not strong enough,

as a few cheap tricks can be used to break each of the IETF standards.

The main problem is that two different messages encrypted with the same

keystream can be x-or-d to produce an x-or of the two messages. The purpose

of including an initialization vector value in the RC4 stream was to ensure

that keystreams were never duplicated. Unfortunately, the WEP IV field is

24 bits wide, this means that in about a half day, the entire spectrum of IV

values is used and the keys start duplicating themselves. This further means

that someone saving all the network traffic can start determining the contents

of packets if they know a the contents of another key encrypted with the same

keystream. Considering the repetative nature of network traffic, that would

not be too hard, one could also send spam to the company and intercept

traffic as everyone checked their email.

The peril of keystream reuse is also exacerbated by the fact that WEP

did not force a good initialization vector scheme. Borisov et [13] al. gave the

example of the orinoco card that started it’s IV cycle at the beginning each

time it was plugged in, and incremented the value by one each time. Needless

to say, it would not be too dificult to compile a list of keystreams (about 24

Gb would be needed) which enable very easy ciphertext decryption.

The checksum on WEP can be over-ridden once ciphertexts are deter-

mined as well. This is because the checksum is a linear function, thus it is

possible to make modifications to the cyphertext that will distribute over

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both the message and checksum underneath. So, if one has good experience

with CMR (complicated math reasons) involved with cryptography, they can

modify the message undetected.

Finally, if one compiles a database of all the possible keystreams, than

one doesn’t need to worry about figuring out the WEP key, they just pick a

random keystream to X-or the packets with, and it will be accepted by the

base station.

Thus, WEP is not an effective long term security measure for use by

companies. While it may deter casual snoopers, a dedicated system cracker

can break in and start reading system traffic. Also, the dropping price of

wireless hardware and the mutable firmware of 802.11 systems makes it easy

for system cracking applications to be written and distributed.

3.5 Current Security Implementations

Today, there are many options for security implementations, WEP, although

not as hard to defeat as IEEE would have liked, is still an effective deterrent

to the casual snooper. Other popular schemes include using Virtual Private

Networks (VPNs), and MAC address restriction.

3.5.1 VPN: security above the link state

VPNs are a scheme that involve all data between a remote user and a private

WAN being encrypted across the internet. It was created so that remote

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users could set up links to their company network over the internet without

having to worry about traffic over the link being secure. This was to avoid

the solution of having to run dedicated network lines to users homes that

circumvented the internet due to security needs. VPNs work in the following

way

1. A VPN client running on the users machine will connect to the VPN

Server on a private WAN.

2. A Secure connection is constructed between the client and server.

3. Communication between the WAN and the remote user occurs securely.

VPN’s would be a good way for ISP’s to ensure that only subscribers were

logging into their network, and since all traffic is encrypted above the link be-

tween wireless user and WAP, security is taken care of as well. Unfortunately,

VPN’s don’t scale well, and could be singled out for DOS attacks.

3.5.2 MAC: allow only registered users

MAC (Medium Access Control) is a scheme used that only allows certain

ethernet hardware addresses to transmit through the network. It requires

that anybody wanting to use the network register with the service provider

so that their MAC address can be stored in a big table on a router somewhere

in the network.

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Because tables of MAC address information would have to be stored and

updated at infrastructure points in the network, this method is also not

scalable beyond several hundred users. It is also possible to spoof the MAC

address of a card, and it doesn’t prevent anyone from casually eavesdropping

on wireless traffic, and is only effective for authentication

4 The Future of Wireless Security

Security in wireless technology has become a major sector of research and

debate in recent years. With the advent of wireless technology holding the

capacity to become the new medium upon which networks can be built, mea-

sures to secure access have become pressing issues. The initial problem with

wireless security comes to a head when trying to resolve clients and Access

Points (AP’s) demands. Individual users demand a network that is capable

of accomplishing simplicity and mobility [14]. APs, however, are primarily

concerned with authentication, authorization, and accounting (AAA) of user

activity. However, there is a common middle-ground that can be achieved

to outline the basic requirements for developing a suite of security tools for

wireless local area networks (WLAN’s) [14]:

1. Mutual Authentication - This quality permits the client and the AP to

properly authenticate each other. It also allows the AP to differentiate

clients.

20

2. Flexible Authorization - Provide the capacity to ensure continued se-

curity by updating and validating clients in some timely manner (i.e.

key freshness etc.)

3. Access Verification - Ensure the safe transfer of data from end-to-end.

4. Interoperability - Allows the client to move between networks without

exceptional overhead, and as smoothly as possible.

5. Data Confidentiality and Integrity - Provide mechanisms to ensure data

transfers are confidential, and allow users to extend their degree of

confidentiality (i.e. using IPsec or TLS).

This outline of requirements encompasses a majority of the demands for

developing security protocols, and will be used as the basis for analyzing a va-

riety of solutions that have been proposed recently. The proposals for increas-

ing WLAN security come in two associated varieties: network layer solutions

and authentication services. Although these solutions are targeted at the

same problem, they are incomplete solutions individually. Through a combi-

nation of these security measures, comfort and confidence with WLAN’s can

be achieved.

4.1 Network Layer Security Implementations

The network layer in ad hoc networks has become an increasingly important

research area, due to its vulnerability to security threats [15]. This layer

21

provides the capacity to route and forward packets of data; an indispensable

component for the proper functionality of a network. Despite the natural

inclination to regard these two functionalities as a singular role in the network

layer, largely due to their dependence upon each other, different security

problems can arise in each of their functionalities, as well as both [15] [16].

There are of course different, but linked, solutions to the problems that can

arise in these two constituents of the network layer.

The current security problems with the routing protocol are two-fold:

external attackers introducing flawed routing information and the nodes ad-

vertising this faulty information [17]. Ad hoc networks, because of their con-

tinually changing topology, compound this security issue; there is no fixed

infrastructure, such as a base station, and thus nodes can rely upon other

nodes to relay data, a responsibility traditionally reserved for a router [16].

Since topology changes in ad hoc networks are common, routing information

can become invalid due to these changes [17]. The solution to prevent er-

rors in routing is somewhat cumbersome, and subject to skepticism for its

ability to maintain efficiency. The most simplistic solution is to solicit the

routing information among nodes, and to perform error checking by diver-

sity coding [17]. While this solution is efficient, it fails to completely prevent

changes to the routing data. Currently, the major proposal under discus-

sion for securing the routing component revolves around changes to the Ad

Hoc On-Demand Vector (AODV) Routing protocol. The central concept to

22

improving AODV relies upon maintaining efficiency, while implementing in-

fallible security; however, many of the solutions accomplish only one of these

goals.

AODV has a multitude of security flaws: impersonation of nodes, forging

Route Error (RERRs) messages, and selectively terminating Route Request

(RREQs) and Route Reply (RREPs) messages [16]. Current proposals for

improving the security of AODV Routing consists of using digital signatures

to validate non-mutable fields, and using hash chains to protect the hop

counts; this routing protocol is currently called Secure AODV, or SAODV

[16]. The unfortunate problem with this implementation is the processing

demands this solution requires from some ad hoc networks to validate the

asymmetric cryptography [16]. However, Nokia Research Center (NRC) has

developed an alternative means to implement AODV security while mini-

mizing processing times, namely NRC-AODV [16]. This improved version of

SAODV is currently under a testing phase, but does require modification for

implementation in ad hoc computer networks. While this satisfies the routing

component, the data component is validated by point-to-point checks, such

as IPsec [16]. The SAODV solution is elegant for the routing component,

but is deficient in the data component given the mutability in topology of

WLAN’s. Therefore, a more suitable solution is desired.

An alternative solution to securing AODV relies upon a pseudo-event

notification system, coupled with tokens signed with a secret key [15]. The

23

solution, as proposed by Yang et. al.[15], is four-fold:

1. Neighbor Verification - A global secret key pair is used to validate

tokens broadcast from other nodes using asymmetric cryptography.

2. Security Enhanced - Routing Protocol - Each AODV maintains a list

called the Token Revocation List (TRL) broadcast by the intrusion

reaction component.

3. Neighbor Monitoring - This component monitors routing updates and

packet forwarding misbehaviors, as well as a form of distributed col-

laboration to assure any single node is in violation of security.

4. Intrusion Reaction - A broadcast system to isolate security violators

and notify network users through the TRL’s.

This solution is convenient because it is designed to be localized, dynamic,

intrusion tolerant, and decreases overhead time compared to the SAODV

solution. However, the employment of asymmetric cryptography, processor

complexity, and storage requirements shed a negative light on the possibility

and scalability of this solution. In addition to the fact that there is some de-

gree of node density required to implement the mechanisms of collaboration,

event notification, and neighbor validation. There are additional advantages

to this solution that allows it to supersede other solutions. The first is the

time-stamped distribution of updates, a parallel with information soliciting

24

used by Zhou and Haas. The salient feature in this implementation, however,

is the protection of both the routing and data components.

As aforementioned, the routing and data components of the network are

to some degree inseparable, and this solution encompasses both components.

The routing information is maintained by asymmetric cryptography within

the AODV, and continual broadcasts among nodes. Secondly, the data com-

ponent is validated by monitoring packet forwarding misbehavior among

nodes, and hence the TRLs [15]. This method can be summarized as using

a variety of algorithms to validate packets, and bolstered by the distributive

collaboration among nodes to ensure monitoring accuracy. Whereby, it sa-

tiates both components of the security requirements outlined for improving

the network layer in WLAN’s. The second component to satisfy a more com-

pletely secure WLAN is the implementation of authentication services that

are scaleable and efficient.

4.2 Authentication Security Implementations

Unfortunately, there is a limited amount of information available concerning

user authentication in a wireless network. However, from the information

available, the most suitable platform suggested so far is the integration of a

authentication protocols used on both hardwired and wireless LANs. Faria

and Cheriton [14] recommend two protocols to authenticate users on a net-

work: the Secure Internet Access Protocol (SIAP) and Secure Link Access

25

Protocol (SLAP) which provide a handshaking method of security for au-

thentication. These protocols are designed to function on top of the preex-

isting IEEE 802.11 protocols, and serve as a replacement scheme for WEP.

The detailed design for implementation allows SLAP to perform additional

security assessments on the network level, by providing the capacity to per-

form message authentication of packets [14]. There is a small amount of

overlap between the two types of security proposals discussed thus far, and

these issues will be discussed after familiarization with the SIAP and SLAP

authentications.

SIAP is designed to function on top of the TCP/IP protocol stack, and is

initially used to provide an authentication handshake between the client and

the AP [14]. SIAP is designed to have each of the clients and AP’s certified

by a known Ceritication Authority (CA), which links the key pair to a DNS

name [14]. There are a handful of functions used to authenticate a client;

through the transfer of public keys and the comparison of data values a user is

authenticated, and establishes the capacity to gain access to an AP [14]. The

inherent problem with this mechanism for authentication relies on the ability

of a server and client to confirm signatures over public keys, which can be

easily solved by using a deployed public-key infrastructure [14]. The absence

of such a system presents a small hurdle, but it can be easily solved using

a local network single-domain certification authority (SOCA)[14]. After the

handshake step, the key values are passed from SIAP to SLAP, which then

26

performs the function of data authentication [14].

The headers that are transferred from this point forward all contain the

SLAP header, and the entire frame is further secured with encryption using

the Advnced Encryption Standard (AES), chosen for its efficiency in both

hardware and software [14]. Once the frame is encrypted, each one receives

a message authentication code that wraps the SLAP header and contents of

the frame. Frames under this protocol architecture undergo reversion upon

their delivery to an end-item (i.e. client or AP). Validation and verification

of frames is performed after their reversion at the end-item, and SLAP uses

the message authentication code to assure the integrity and identity of the

sender [14].

In order to assure the efficiency of this architecture, SIAP messages in-

tended for the AP are not processed using the SLAP module, allowing the

client to assure access authority before associating with an AP [14]. Once a

client is associated with an AP, all messages use the SLAP protocol to com-

municate with the AP. Given the dynamic topology of WLAN’s, each SIAP

association to an AP is unique, and therefore in transferring from one AP

to another, the SIAP client must broadcast its state, and obtain validation.

There are several key features to this design that constitute the SIAP and

SLAP architecture as effective, scaleable, and promising.

The first of these features is the ability to make this standard applicable

to WLAN’s interfaced with hardwired LAN’s, allowing the individual entities

27

to be completely interoperable with the currently existing Ethernet hardware

or default gateway [14]. Additionally, since SIAP is completely independent

of the link layer, it is possible for this protocol to implemented in the IEEE

802 family [14]. Additionally, these added benefits to the design of wireless

security can be implemented on top of IEEE 803 standards, and thus pre-

vents the necessity to create multiple wireless standards; this attests to the

simplicity of the SIAP and SLAP architecture.

4.3 Conclusions

As stated earlier, in order to assure the security of a wireless network, some

compromise must be reached in regard to resolving the protocols to use. The

SIAP and SLAP architecture seems to perform the duties of data integrity

on the network layer quite effectively, as well as efficiently, and therefore is

the outstanding architecture to implement client authentication (points 1,

3, 4, and 5 from the outline for security tools suite). The only real failure

point of this system is the ability to maintain the routing component of the

network layer, which received little attention despite the ramifications for

forgoing its security. However, SAODV is an appropriately matched solution

of improving routing security, and is limited to this functionality in its design

(point 2 from the outline for security tools suite). However, SAODV does

need to improve its speed and processor requirements in order to be a suit-

able companion for increasing security. Therefore, by combining the SIAP

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and SLAP architecture, with an improved version of SAODV, possibly as a

derived form of NRC-SAODV, the potential for creating an airtight wireless

security protocol is extraordinary. Whereby, the elimination of WEP can be

achieved, and the potential for ubiquity maximized.

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