Security Issues, Concepts and Strategies in Wireless And

Mobile SystemsBy: Imad Jawhar

Outline

• Introduction

• The wireless environment and systems

• Concepts and terminologies used in wireless security

• Some commonly used wireless and mobile systems and protocols

• Wireless application protocol (WAP)

• Wireless transaction protocol (WTP)

• Wireless transport layer security (WTLS) protocol

• Some additional concerning WAP security

• Some research and future directions in wireless system security

• Conclusions

The Wireless Environment

• Communications in the wireless environment has its own issues and challenges.

• Generally, it has the following characteristics:– Relatively low bandwidth and data rate.

– Relatively high error rates.

– Need for low power consumption to preserve battery life of mobile systems.

– Mobility of the nodes adds more complexity because of topology changes.

– Signal fading.– Handoff issues.– And other challenges.– All of these issues affect design and design for

security

• There exists many forms of wireless communications and networking, and the number of these forms dynamically increasing.

• The following is a list of the some very popular forms of wireless communications.

• Satellite Communications:– Uses microwave links and provides global

connection of many network infrastructures.– Three types of satellites:

• GEO: Geostationary Earth Orbit Satellites.

• MEO: Medium Earth Orbit Satellites.

• LEO: Low Earth Orbit Satellites.

• Cellular Networks:– Widely used recently. Quickly increasing in

popularity all over the world.– Geographic area is divided into cells.– Each cell is serviced by a base station (BS).– Several stations are served by a Mobile

Telecommunications Switching Office (MTSO), or a similar structure.

– Base station connects mobile users to MTSO.– MTSO connects base station (BS’s) to

telephone switching office.– The first generation of systems was AMPS

(Advanced Mobile Phone Service) which used analog communications

• The second generation uses digital traffic channels, encryption, error detection, correction, and allow channel access to be dynamically shared by all users.

• Third generation systems will have:– Voice quality that is comparable to public

switched telephone networks.– Higher data rates.– Symmetrical and asymmetrical data

transmission rates.– Support for both packet and circuit switched

data services.

– Adaptive interface to the Internet to reflect common asymmetry between inbound and outbound traffic.

– More efficient use of available spectrum– Support for wide variety of mobile .equipment.– More flexibility to accept new services and

techniques.

• Cordless Systems:– Used inside homes and buildings.– Allow wireless communications between

cordless devices such as a telephone to a single multiple base stations using TDMA (Time Division Multiple Access) and TDD (Time Division Duplex) communications.

• Wireless Local Loop (WLL):– Increasingly more popular way to provide

wireless last mile connections between the end user and the local switching telephone center.

– Allows reduction in installation cost, and time.– Selective installation is possible (only install

when customer desires service, not in anticipation of the customer desiring service).

• Mobile IP:– Allows nomadic access to the Internet from

different access points.– A user is able to maintain connectability to the

Internet while moving from one access point to another.

– It uses process registration, agent solicitation, move detection, and tunneling to achieve this objective.

• Wireless Local Area Networks (WLANs):– Rapidly becoming very popular.– This is due to many characteristics such as:

• Need for mobility.

• Cost effectiveness.

• Convenience.

• Rapid deployment ability.

• Decrease in size of electronic and digital equipment.

• Speed of mobile computing devices.

• There are four types of wireless LANs .

• LAN Extension:– Provide wireless connections of mobile

computing units to a wired network.– Used in manufacturing, stock exchange, and

warehouses.

• Cross-building Interconnect:– Used to provide wireless connections between

buildings.– Uses microwave communications with dish

shaped antennas.– More of a link than a LAN.

• Nomadic Access:– Used to provide connectivity from mobile units

such as a laptop, PDA or other computing devices to a fixed campus network per example.

• Ad Hoc Networking:– Also called rapidly deployable networks.– An increasingly popular form of establishing

networks between mobile computing devices, such as laptops, computers inside moving vehicles.

– The temporary wireless network is established dynamically on the fly.

– Very dynamic in nature because topology changes while nodes move from one location to another, and nodes dynamically move in and out of each other’s range and are added and deleted to the network all together.

– Require robust communications algorithms and protocols, which have the following characteristics:

• Can quickly adapt to the changing network topology.

• Maintain efficient connectivity and routing between various nodes while wireless links are lost and established dynamically as nodes move in and out of each other’s range.

– There are numerous applications for Ad Hoc Networks, such as:

• Tactical military operations.

• Conferences.

• Campus and classroom environments.

• Disaster recovery.

• Search and rescue operations.

• And so on.

• Bluetooth:– A wireless communications protocol.– Originally started by Ericsson.– Quickly became adopted by a consortium of

companies in the computer industry.– Grew from a few companies to thousands

including all of the major companies in the industry.

– Designed to establish and maintain connections between various computing devices and electronic equipment such as: Computers, cellular phones, PDA’s, and so on.

– This is done wirelessly avoiding the need for wires to establish the connections.

– Intended to work in a close proximity environments such as homes, offices, classrooms, hospitals, airports, etc.

– Connections are established by designating master and slave nodes.

– It uses profiles for different devices, which characterize the applications.

– There are types of communication links which are multiplexed over the same RF (Radio Frequency):

• Synchronous Connection-oriented (SCO) for voice.

• Asynchronous connectionless (ACL) links for data.

– Uses Frequency-hopping spread spectrum with a high rate 1600 hops/sec to reduce interference, and provide low power, and low cost of radio communications.

– Operates in the ISM band at 2.45 GHz with a transmission of 1 to 100 mW, and a range of 10 to 100 meters, and a maximum bit rate of 1 Mbps, and an effective data transfer rate of 721 Kbps.

802.11 wireless standard

• This is a wireless LAN standard.• which is increasingly being adopted by

many wireless devices to establish communications at the physical and data link layers of the OSI model.

• In 2000 vendors sold around a million 802.11 network interface cards, and sales are expected to go up to 3.9 million in 2004

Security Issues

• Importance of wireless systems.• In every aspect of our lives.• Sensitivity of information shared on

wireless systems (increasingly important) financial, personal, social, confidential, etc.

• example: wireless cameras (watching nanny and baby in house…the whole block watching).

Security services needed

• (especially in e-commerce transactions)

• User authentication: The process of proving to the system that the user is whom he/she says he/she is.

• Data authentication: It is further subdivided into two sub-services.

• The first is data integrity, which is the process of guaranteeing to the receiver that the data was not changed during the transmission process.

• The second is data origin authentication is the process of proving to the receiver that the data was actually sent by the stated sender.

• Data confidentiality: It ensures that unintended parties are not able to read the data while in transit. Encryption is used to achieve this objective.

• Authorization:• It is the process of ensuring that only authorized users are

allowed to access the data/resources. In a “closed system” a user is not allowed access without explicit authorization. Typically, this is the desired model of secure systems. On the other hand, in an “open system” a user is allowed access (implicit authorization) unless specifically deauthorized by the system. The latter model is undesirable for the design of secure systems, unless absolutely necessary because of the nature of the application (a public library, etc.)

• Audit: An audit trail is used to keep track of who, when, what, and how transactions took place in a system. This audit trail can be an essential tool for after the fact analysis in cases intentional or unintentional security attacks. It can also be used by intrusion detection algorithms to detect and prevent current and future attacks.

• Non-repudiation: This is an important service that is essential for the proper operation of certain e-commerce transactions. It is the process of guaranteeing that a certain user actually did issue a certain order or required a certain transaction. Non-repudiation is usually implemented using digital signatures, which are unique to users and provide proof that a particular user initiated a particular transaction.

• Some Commonly Used Mobile and Wireless and Mobile Systems and Protocols:

• 802.11

• Bluetooth

• Mobile IP

IEEE 802.11

• This is a wireless LAN standard.• which is increasingly being adopted by

many wireless devices to establish communications at the physical and data link layers of the OSI model.

• In 2000 vendors sold around a million 802.11 network interface cards, and sales are expected to go up to 3.9 million in 2004

• The 802.11 architecture uses the wired equivalent privacy protocol (WEP).

• Data is encrypted with WEP to protect the wireless link between clients and access points.

• Network administrators distribute a WEP-algorithm-based key for authorized users, which prevents access by unauthorized users.

• The protocol has authentications, deauthentication (this service is invoked whenever an existing authentication is to be terminated), and privacy provisions [1] [3].

• Authentication (and deauthentication) services are used for establishing identity of a station.

• The standard does not specify any particular authentication scheme.

• Privacy services are used to prevent the content of messages from being read by other than intended recipients [3].

Bluetooth

• This is a wireless communications protocol, which was originally started by Ericsson.

• quickly became adopted by a consortium of companies in the computer industry.

• The consortium grew from a few companies to thousands including all of the major companies in the industry.

• It is designed to establish and maintain connections between computing devices, and electronic equipment, such as computers, PDA’s, cell phones, and so on, wirelessly avoiding the need for wires.

• It is intended to work in a close proximity environment, such as homes, offices, classrooms, hospitals, airports, etc.

• Connections are established using designated master and slave nodes.

• It uses profiles for different devices, which characterize the applications, synchronous connection-oriented (SCO) for data, and asynchronous connectionless (ACL) links for voice, which are multiplexed on the same RF link.

• Frequency-hopping spread spectrum with a high 1600 hops/sec rate is used to reduce interference, and provide low power, low cost radio communications.

• It operates in the ISM band at 2.45 GHz with a transmission power of 1 to 100 mW and a range of 10 to 100 meters, and a maximum bit rate of 1 Mbps, and an effective data transfer rate of 721 Kbps.

• Up to 8 devices can communicate in a Piconet with one device acting as the master and the other devices as slaves. Several Piconet in one area can form a “Scatternet” in which all nodes use the same frequency range with each “Piconet” using a different hop sequence.

• The bluetooth baseband specification defines a facility for link security between any two Bluetooth devices, consisting of the following elements [3]:

- Authentication

- Encryption (privacy)

- Key management and usage.

• The security algorithms use four parameters:– Unit address: The 48-bit device address, which

is publicly known.

– Secret authentication key: A secret 128-bit key.

– Secret Privacy key: A secret key of length from 4 to 128 bits.

– Random number: A 128-bit random number derived from a pseudorandom generation algorithm executed in the Bluetooth unit.

• The two secret keys are generated and configured with the unit and are not disclosed.

• The authentication process is used to provide verification of the claimed identity of one of the two Bluetooth devices involved in an exchange.

• Authentication is done by verifying that the two devices share the same preconfigured authentication key.

• Encryption of packet payload can be used to protect user information. The access code and the packet header are never encrypted.

• The encryption is done using an encryption algorithm known as E0 [3]. For each packet transmission, a new encryption key is generated.

• The algorithm generates a one-time payload key by combining in a complex fashion a random number, which is sent to the slave, the master's address, the current clock value and a shared secret key. Because the clock value changes for each encryption, a different encryption key is used each time, enhancing security.

Mobile IP• It is used to enable computers to maintain

Internet connectivity while moving from one Internet attachment point to another.

• It uses the concept of home and foreign networks and home and foreign agents.

• Messages intended for a certain node, which are sent to its home network, are forwarded to a care of address to the mobile node at the foreign network where it is registered previously when the move was detected.

• The forwarding process uses datagram-tunneling and encapsulation options, which include IP-within-IP, minimal-encapsulation, or Generic routing encapsulation (GRE) [3].

• Mobile IP has security features, which are essential to its operation. This is because a wide variety of attacks could be used by an unauthorized user to access information of another user.

• It uses message authentication, registration request and reply contain authentication extensions with security parameter index (SPI) and authenticator.

• Authentication procedures are carried out to secure mobile-home (mobile node/home communication), mobile-foreign (mobile node/foreign agent communications), and foreign-home (foreign agent/home agent communications).

Wireless Application Protocol (WAP)

• This is an open standard, which provides mobile users of wireless terminals such as wireless phones, pagers, and PDA’s access to telephony and information services [3].

• It is designed to work with all wireless network technologies such as GSM, CDMA, and TDMA.

• It is based on existing Internet standards such as IP, XML, HTML, and HTTP [3] [10] [9] [12].

• The WAP forum is an industry association of over 500 members “that has developed the de-facto world standard for wireless information and telephony services on digital mobile phones and other wireless terminals” [16].

• In the latest class of secure wireless protocols from the WAP Forum, client-side certificates are specified and used as part of client-side authentication and non-repudiation services [10].

• Users are able to access e-commerce sites from new wireless devices such as PDAs and mobile phones.

The WAP Specification:

• WAP defines an open, standard architecture, and a set of protocols for the implementation of wireless access to the Internet.

• The WAP specifications include [14] [3]:

• An XML-type markup language, Wireless Markup Language (WML): It has text and image support with formatting layout and commands.

• Deck/card organizational metaphor (documents subdivided into cards which specify one or more units of interaction), and support for navigation among cards and decks.

• A sample of WML code, consider the following simple deck with one card [20].

• <wml>• <card id=’card1’>• <p>• Hello WAP World.• </p>• </card>• </wml>

• The tags <wml>, <card>, and <p> enclose the deck, card, and paragraph, respectively. When a wireless device receives this code, it will display the message “Hello WAP World” on the terminal’s screen.

• The book in [3] has a table with all of WML tags, which are divided into eight functional groups: Deck Structure, Content, Formatting, User Input, Variables, Tasks, and Task/Event Bindings. Refer to [3] [12] for more information on the WML language.

• A “microbrowser” specification: It defines how WML and WMLScripts are determined in the wireless device.

• A lightweight protocol stack: Wireless Session Protocol is equivalent to HTTP in a compressed format. Designed to minimize bandwidth use allowing different wireless networks, with varying bandwidth capacities, to run WAP applications.

• Framework for Wireless Telephony Applications (WTA): It provides access to traditional telephony services (such as Call Forwarding) through WMLScripts.

• Provisioning: It allows Service Providers to reconfigure mobile devices remotely using Short Messaging System (SMS), which is a GSM standard [17].

Components of the WAP Architecture

• The WAP model consists of three elements: the client, gateway, and original server. This is shown in figure 1.

• The gateway serves as a proxy, which connects the wireless device/s to the original server.

• HTTP is used to communicate between the gateway and the original server.

• The WAP gateway performs functions, which are spared from the relatively less capable processor in the wireless devices.

• It provides DNS service, converts between the WAP protocol stack (protocols that have been optimized for low bandwidth, low power consumption, limited screen sized, and limited storage) and the traditional WWW stack which includes HTTP and TCP/IP.

• encodes/decodes information from the wired web to more compact form.

• which is more easily digested and displayed by the more limited wireless device.

• This reduces the amount of data communicated wirelessly.

• The gateway also reduces communication overhead and latency by caching recently requested web pages and information.

Figure 1 – The WAP Programming Model.

Client Original Server

WAE user agent

Gateway

Encoders andDecoders

Content

CGIScripts, etc.

Response (content)Encoded response

RequestsEncoded requests

• WAP specifications have several components to provide secure communications.

• These components include the WTLS protocol, WAP identity module (WIM) smart cards for storing user certificates, and functions such as Crypto.signText(), which is used for signing of WAP transactions.

• As shown in figure 2, the WAP Protocol Stack is a layered architecture which consists of several protocol layers.

• We will briefly describe each of the layers and focus on the the WTP and WTLS layers in this paper.

• On top is the Wireless Markup Language (WML) (described later), and WMLScript layer, which is a scripting language with similarities to JavaScript.

• Below WML and WMLScript is the Wireless Application Environment (WAE) layer, which specifies an application framework for wireless devices such as mobile phone, pagers, and PDAs.

• WAE consists of tools and formats that are designed to ease the task of developing applications and devices supported by WAP.

Wireless Application Environment (WAE)

Wireless Transaction Protocol (WTP)

Wireless Session Protocol (WSP)

Wireless Transport Layer Security (WTLS)

Wireless Markup Language (WML) WMLScript

Wireless Datagram Protocol (WDP)

UDP

GSM

IP

D-AMPS IS-95 3G Bluetooth

Figure 2 – WAP Protocol Stack.

• The WAE layer is followed by the Wireless Session Protocol (WSP).

• WSP provides applications with an interface for two session services connection-oriented operating over the Wireless Transport Protocol (WTP) (comparable to TCP on the in wired networks) and connectionless operating over the unreliable transport protocol called Wireless Datagram Protocol (WDP) (comparable to UDP in wired networks).

• Basically, WSP is based on HTTP with some modifications and additions to optimize its use over wireless links.

• Below the WSP layer, resides the Wireless Transaction Protocol (WTP), which will be described later.

• Then below WTP, resides the Wireless Transport Layer Security (WTLS), which will also be discussed later.

• Below the WTLS layer, follows the Wireless Datagram Protocol (WDP), which in turn operates on top of the a number of bearer service providers such as GSM, D-AMPS, IS-95, 3G, Bluetooth, etc.

• We will only concentrate on the WTP and WTLS layers in this presentation.

Wireless Transaction Protocol (WTP)

• WTP manages transactions by conveying requests and responses between a user agent (such as a WAP browser) and an application server for such activities as browsing and e-commerce transactions [3].

• It provides reliable transport services without the undesirable overhead of TCP, which is the transport layer protocol, used in wired networks.

• This results in a lightweight protocol more suitable for implementation in “thin” clients (such as wireless/mobile devices) and over low-bandwidth wireless links.

• It includes the following features: – Optional user-to-user reliability: WTP user triggers

the confirmation of each received message.– Optional out-of-band data on acknowledgments.

– PDU concatenation and delayed acknowledgment to reduce the number of messages sent.

– Asynchronous transactions.– Three classes of transaction services to provide:

unreliable datagram service, reliable datagram service, and request/response transaction service and support the execution of multiple transactions during one WSP session.

The Wireless Transport Layer Security (WTLS) Protocol

• The WAP protocol stack includes security features in its Wireless Transport Layer Security (WTLS) layer, which is directly below the Wireless Transaction Protocol (WTP).

WTLSHandshakeProtocol

WTLS AlertProtocol

WTP

WTLS Record Protocol

WTLS ChangeCipher SpecProtocol

Figure 3 – WTLS Protocol Stack

WDP or UDP/IP

• Security of WAP transactions is achieved using the WTLS protocol [18] [3].

• The WTLS protocol provides entity authentication, data confidentiality, and data integrity.

• It is based on the IETF SSL/TLS protocols [10][19]. WTLS provides security for communications between the WAP wireless device and the WAP Gateway.

• As shown in figure 3, the WTLS Protocol Stack includes WTLS handshake protocol, WTLS Change Cipher Spec Protocol, WTLS Alert Protocol, and WTP at the top. Below resides the WTLS Record Protocol, which in turn lays on top of the WDP or UDP/IP layer.

• The function of the WTLS Record Protocol is to take the user data from the next higher layer (WTP, WTLS handshake protocol, WTLS Alert Protocol, WTLS change cipher spec protocol) and encapsulates the data in a PDU (Protocol Data Unit) [3].

• The PDU contains the data in a compressed, and encrypted form with a WTLS record header appended to it. Encryption is done using a symmetric encryption algorithm. The allowable encryption algorithms are DES, triple DES, RC5 and IDEA [13].

• The WTLS protocol has three different classes of service [10]:– Class 1: This class implements

unauthenticated Diffie-Hellman key exchange to establish the session key. Early WAP devices only implement this level, which is insufficient and should not be used for e-commerce transactions [21].

– Class 2: This class enforces server side authentication using public key certificates similar to SSL/TLS protocol. The WAP Gateway uses a WTLS certificate, which is a particular form of X.509 certificate compressed to save bandwidth. This level is used in currently available devices, which are being used in several read-only access and in-economy banking applications in Europe and the UK [22].

– Class 3: Using this class, clients are able to authenticate using client side certificates, which are regular X.509 format. These certificates can be stored either on the client or on a publicly accessible server with a pointer to the certificate stored in the wireless device. This class is beginning to be used in wireless phones [23].

• Nokia, KPN Mobile, and Interpay Nederland have successfully tested financial transaction on a mobile network [23], based on WIM technology, which is a part of the WAP 1.2 (Wireless Application Protocol) specification.

• With this real time payment solution, a mobile telecommunications network operator, a mobile phone and infrastructure manufacturer and a payment processor have made improvement in security for mobile commerce transactions.

• The solution is based on WIM (Wireless Identity Module), which is a mobile Internet technology enabling more secure transactions.

• Non-repudiation of transactions is ensured by a digital signature. In practice, this means users can perform transactions safely using a single PIN-code.

• In addition, built-in security elements in the terminal and network ensure more secure and reliable transactions.

• Class 3 security services, which are in the process of being offered by different wireless device manufacturers such as Nokia and Motorola, are expected to allow banking institutions to enhance their current wireless e-commerce services to allow “out-of-economy” transactions.

• As shown in figure 3, the WTLS protocol stack also contains the following protocols:

• The Change Cipher Spec Protocol: – The cipher spec is associated with the current

transaction.

– It specifies the encryption algorithm, the hash algorithm used as part of HMAC, and cryptographic attributes, such as MAC code size. This protocol is used in the process of establishing the cipher suite used for subsequent communications during a session.

• The Alert Protocol: – Used to convey WTLS-related alerts to the peer entity.

Alert messages are compressed and encrypted as well.

• The Handshake Protocol in the WTLS:– It allows the server and client to authenticate each

other and to negotiate an encryption and MAC algorithm and cryptographic keys to be used to protect the data sent in the WTLS record. The Handshake protocol is used to establish the security provisions before any application data is exchanged [3].

Some Additional Issues Concerning WAP Security:

• Research has identified some additional issues regarding the security of WAP based systems. The following are some of these issues.

• About Maintenance of the WAP Gateway:– The WAP Gateway can be maintained by the

Wireless Service Provider (WSP) or by the Enterprise (on the server side).

– If the WSP maintains the WAP gateway however, some literature [10] refers to the presence of a security “gap” caused by the ending of the Wireless Transport Layer Security (WTLS) session at the Gateway.

– The data is temporarily in clear text on the Gateway until it is re-encrypted under the SSL session established with the Enterprise’s web server.

– In such cases, the WAP Gateway should be maintained at the Enterprise. A more detailed discussion of this issue is presented in [10].

• The WAP Identity Module (WIM):– New generation of WAP phones will provide

WIM to facilitate client side authentication [24]. WIM is used to implement WTLS protocol Class 3 functionality.

– It has embedded support for public key cryptography. With the WIM implementation, RSA [21] is mandatory and Elliptic Curve Cryptography [21] is optional.

– Smart card is one possible implementation of WIM. It could be a part of the SIM (subscriber identity module) card in a cellular phone (in GSM [17]) or an separate smart card (WIM card).

– A combination of SIM-WIM card is typically called a SWIM card. The WIM card would be configured by the manufacturer with two sets of private-public key pairs (one for signing and one for authentication), and two manufacturer’s certificates.

– All WTLS sessions established through a WIM and a WAP Gateway will use the same public keys for initial session negotiations.

– A WIM is able to store a number of certificates or user certificate references, such as a URL-based reference.

– A user will be required to register a certificate at each Enterprise (such as a Bank, etc.).

– The WIM must be tamper resistant to make it not feasible to extract or change information in the module, because it contains user private keys, which never leave the WIM.

User Identification and Authentication in WAP

• The type of user identification and authentication possible in WAP differs with the WTLS class of service used.

• Username/password identification and authentication can be used with WML forms exchanged between the server and the wireless device.

• It is also possible to have client-side identification and authentication based on the public/private key pair that is hardcoded on the WIM card and bound with the user’s name in their certificate.

• Non-repudiation in WAP: – It requires client side certificates that bind the

user’s signing key with their name. – The WAP browser, on the WAP device,

provides WMLScript function, Crypto.signText() [25], which achieves this purpose using different scenarios depending on the implementation.

Some Research and Future Directions in Wireless Systems

Security• What is Secure Sockets Layer (SSL) ?

– SSL is the most widely deployed and used security protocol in the world.

– Essentially every commercial Web browser and server supports secure Web transactions using SSL.

– You are almost certainly using SSL every time you buy online using “secure” Web pages [13]. Currently, tens of billions of dollars worth of SSL transactions occur per year.

– SSL is mostly used for securing Web traffic transactions, however, it is a general protocol suitable for securing many other types of traffic.

– In addition to the World Wide Web, SSL and its successor, Transport Layer Security (TLS), are used in other popular applications such as File Transfer Protocol (FTP), remote object access (RMI, CORBA, IIOP), e-mail transmission (SMTP), remote terminal service (Telnet) and directory access (LDAP) to secure their transactions.

– As will be shown later in this paper, SSL is currently being used in different stages of the transaction communications between wireless devices and the wired infrastructure.

On Using SSL in Wireless Communications

• Due to the perceived relative decrease in capabilities of wireless device CPUs and lower bandwidth capabilities of wireless channels, there is a drive away from SSL and toward security architectures designed for wireless transactions that lack end-to-end security.

• However, some literature [6] show that SSL is a practical solution for end-to-end transaction security of wireless Internet applications even considering the limitation of the wireless devices and environment.

The Development of Lightweight Security Mechanisms for Wireless Multimedia

Traffic Transmission

• In addition to the above protocols, and architectures, research is being done in order to design “lightweight” encryption algorithms for MPEG video transmission.

• In [7], researchers propose to provide encryption of video data while increasing the decodability of the video stream in the presence of errors.

• These algorithm explore the predictable relationship between the I, P, and B-frames of compressed video, and decrease the expected number of bit errors left in the data after encoding.

• For more information on these techniques the reader is referred to [7].

On Security of Mobile Phone Communications

• Furthermore, some research is being done on the security management planning for telecommunication systems, with focus on intrusion detection and cloning mobile phone problems.

• In [8], researchers discuss mobile phone network security management planning with its various aspects such as access control, confidentiality, authentication, non-repudiation, and integrity of data communications.

• The research also addresses intrusion detection systems design for mobile phone communications.

• Intrusion can be classified as: (i) misuse intrusion, i.e., well defined attacks against known system vulnerabilities; and (ii) anomaly intrusion, i.e., activities based on deviation from normal system usage patterns.

• Intrusion detection systems are considered effective security tools to defend against such attacks [8].

• Research shows that current software in mobile phone systems – (i) do not have an efficient scheme to verify if a call is

out of the client patterns of communications (in most of these systems human staffs are used to identify cloned phones and warn their clients in such situations);

– (ii) have no efficient ways to control and identify the impostor; and

– (iii) use an “experimental satisfaction” to prove the correctness of their security mechanisms. Better, and more automated techniques for security management and identification of frauds, and impostors using cloned mobile phones are needed.

– Some research uses neural network techniques to classify phone users into groups according to their past/current profiles. It is then relatively easy to determine whether a call was made by the actual subscriber, or an impostor/intruder [8]. Such technology can be very effective in battling and preventing cloning of mobile devices and consequently result is substantial savings and more security and privacy for wireless service providers and their customers.

Concluding Remarks

• Wireless systems are quickly becoming an important and increasingly essential part of our every day activities.

• They provide unlimited potential for convenience, more independence, portability, availability, instantaneous, and ubiquitous connectivity wherever we go.

• They promise great financial gains to the companies that invest in the development, marketing, sales, leasing, maintenance and use of these quickly evolving and increasingly smaller, easily portable, and progressively more intelligent products.

• Wireless devices are expected to hold and communicate a large amount of data and information about every aspect of our lives.

• They are also expected to carry out numerous, important, and sensitive financial transactions, which can only be done in a relatively secure and well-protected environment.

• This protection and security is required to varying degrees depending on the application involved.

• The authors in [6] argue that the use of proxy based architectures in popular environments such as WAP and Palm.Net, where a different security protocol (incompatible with SSL) is used between the mobile client and the proxy/gateway (e.g. WAP uses WTLS [16] and Palm.Net uses a proprietary protocol on the wireless link) has some drawbacks.

• This is the case, since the proxy constitutes a “man-in-the-middle” which is involved in all “secure” communications, in addition to being a potential performance bottleneck.

• Some experiments show that SSL, which is a well-tested and evaluated technology, is able to be practically and efficiently used in current and the future wireless and portable devices.

• This is particularly the case considering that the capabilities of the CPU’s, memory, and bandwidth of these devices is significantly improving every day.

• This efficiency is achieved by carefully selecting and implementing a subset of the protocol’s many features (Full versus abbreviated SSL handshake per example, etc.) to ensure acceptable performance and compatibility with a large installed base of secure web servers.

• All this can be done while maintaining a small memory footprint. This is in concert with the concept stated by the Ice Hockey Legend, Wayne Gretzsky who said: “Don’t skate to the puck; skate to where it’s going” [6].

• Wireless systems’ full potential and promise can only be realized if the security aspects of these systems are well considered.

• Proper design and implementation must be done according to sound security principles, which must be employed throughout the analysis, design, implementation, testing, and maintenance phases of these products and systems.

• During their initial inception and the first years of their introduction to the market, security was not a major concern or design objective.

• However, this is quickly changing to take a proper high priority in the design and implementation of wireless systems.

• Considerable amount of research has been and is being done to provide for more secure wireless systems at every level of their architecture.

• This research is needed to provide security mechanisms at the level of the portable device as well as the supporting wired and wireless system infrastructures.

References1. Sandra Kay Miller, “Facing the Challenge of Wireless Security”, IEEE Computer. July 2001.

Pages: 16-18.

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