Secure Tracking System for Cashboxes
Today the money is transported around the nation to banks and cash machines via security vehicles. Once the vehicle has arrived at its destination, the cash is deposited inside a secure container and Physical security guard transports this to its desired location. Upon reaching the destination, the cash-box is prone to various threats mainly being theft. The cash-box theft is the major issue that all banks suffer these days. Only physical security is not sufficient to protect very large amounts of money. We have various wireless technologies to control, monitor and track the mobile assets. The tracking scenarios are boosted by the invention of Radio Frequency Identification (RFID), Global Packet Radio Service (GPRS) and Global Positioning System (GPS). By making using the above specified technologies, one can trace the movements of the security vehicle or even cash-box efficiently with graphical maps and location information stored in the backend database. If the theft of cash-box is detected, tracking system can be activated to trace the path of cash-box. Once tracked and located, through the monitoring system, we can easily retrieve it or even catch the criminals.
This assignment discuss the above issue of detecting and tracking the cash-box by using wireless technologies like RFID, GPS, GSM, GPRS and EGNOS. GPRS serves as the communication backbone of the system while GPS/EGNOS plays the role of locating the box and RFID is used for theft detection. The assignment also briefly describes the technologies used in the system, its benefits and disadvantages and technical and security drawbacks. Finally a framework is developed by making use of above listed technologies to perform the required task.
2. Technological Description:
2.1 Global Positioning System (GPS)
GPS is a Satellite-based navigation system containing a network of 24 satellites placed in space orbit that provides reliable positioning, navigation and timing services to any users on continuous worldwide basis. For anyone with GPS receiver, the system will provide location (latitude, longitude and altitude) and time. GPS is made of three parts: satellite orbiting earth, control and monitoring station and GPS receiver (U.S Government, 2010).
The satellite revolves around the earth two times in a day and in a precise orbit while doing that it transmits a signal to the earth. This signal is received by GPS receiver and using that information and triangulation it calculates the use's exact location. GPS receiver compares the time when the signal was transmitted to the satellite and the time when the signal is received which shows how far the GPS receiver from the satellite is and calculate the exact position. To get the 2D position GPS receiver has to compare distance with at least 3 satellites. With four or more satellite GPS can calculate 3D position. Due to parallel multi channel design GPS is very much accurate (Garmin, 2010). Often this GPS receiver is used in war craft, airplanes and automobiles Such as in rental car you often find this navigation system based on GPS which help them whenever there is twist and turn.
So far we have seen what GPS is and how does it work? But when it comes to use of technology we need to look for the advantages provided by the particular technology:
- Theft Protection: As I have said earlier now a day lot of organizations, banks are facing a problem of robbery. While transferring money from one location to another location there is a possibility of money is being stolen.
- Using GPS technology organizations or banks can locate the position of the cashbox in which money has been kept since it provides exact location of the object. (Linsell, P. 2002)
So far we have seen advantages of the GPS system similarly there are few disadvantages of this system:
- The signals sometimes patchy which make it difficult to identify the location at all the time.
- It does not work indoors and underground which limits the use of technology for various purpose.
- Purchasing GPS service is not a costly affair but GPS technology is expensive which might take thousands of pounds.
- There are various ways to spoof satellite signals such as there are certain limits from where you do not get the signal so identify the exact location. (Garmin, 2010)
Similarly there are various factors that could affect the strength of the GPS signal:
- Ionosphere and troposphere delays: i.e. in satellite signal slows down in atmosphere so the GPS receiver calculates the average speed to correct the error.
- Signal Multipath: This occurs when the GPS signal is reflected due to tall buildings or an object which increases the travel time of the signal. Receiver clock error: i.e. no an accurate clock. Number of satellite visible: More the number of satellite visible better is the quality of signal but taller buildings or objects hide the satellite from receiver causing position error. (Garmin, 2010)
GPS uses an exceptionally weak signal from the satellite which is equal to viewing a 25W bulb from a 20,000 KM distance from space (ag.gov.au, 2010). Also GPS is of dual use where in used by both Civilians such as mobile users and industries alongside with Defense department. This makes the technology more vulnerable to any attack from a hacker. Some of the vulnerabilities present in a GPS that result in getting hacked are:
Intentional Jamming: This is one way of denying the GPS signals by jamming the signals using Radio Frequency interference. It is found to have been one of the most significant ways to jam the signals and carry out the denial of signals attack on any system that uses it. (ag.gov.au, 2010)
Unintentional Jamming: It can be due to a possible interference from a nearby Radio frequency interference or nearby mobile reception that can cause the jamming. Some of them being nearby Television signals, mobile signals, radio frequency etc.
Signal Spoofing: A more deliberate form of GPS signal jamming may be termed as GPS Spoofing. Here, the Spoofer deliberately fakes or mimics a genuine GPS signal and meanwhile the GPS receiver would think that the spoofed signal from the hacker is genuine and keep receiving it. Thus by faking the signal, the Spoofer would normally send false information such as wrong latitude, location, etc.(ag.gov.au, 2010)
2.2 EGNOS for improving GPS positioning:
In this tracking system, additionally to GPS, we would be using EGNOS (European Geostationary Navigation Overlay Service) technology. Among emerging demands about tracking and location based services related to land navigation, many organizations require more accurate positioning system than for common usage. A positioning system is expected to provide its best performances in urban environment, which cannot be delivered exactly by GPS receiver's behavior.
EGNOS is able to greatly enhance the availability of accurate GPS positioning in typical urban area where the street density is higher. When buildings are masking some satellites, poor system geometry is experienced. As described earlier, GPS receiver has no need to be in line of sight with EGNOS geostationary satellites to receive corrections. This is achieved through the SISNeT server that makes possible to receive corrections from any alternative telecommunication or broadcasting network.
An EGNOS-SISNeT powered receiver provides much better availability of accuracy than a GPS-only receiver for typical urban environments. While in all in view situations, typical EGNOS accuracy (95%) performances will be of the order of 1-2 meters (vs. 10-20m of GPS-only) while GPS-only receivers provide 0%.
These results, linked to the minimum extra complexity of a GPS-SISNeT powered receiver versus a GPS-only receiver, justifies the interest of providing EGNOS corrections through complementary means to GEO broadcasting (BONNET C, 2004).
2.3 Global System for Mobile communications (GSM):
GSM is a global mobile standard for mobile communication which is managed by GSM Association and so far more than 80% of the users and network operators using the GSM standard. Initially when GSM was designed in the year 1982, it came out with a moderate level of security. The entire system was designed to authenticate the subscriber using a pre-shared key. This is done by encrypting the messages that are communicated between the subscriber and the Base Station. GSM uses several cryptographic algorithms for ensuring the security of its service. Some of the popular are theA5/1andA5/2stream ciphers used mainly for ensuring over-the-air voice privacy. A5/1 is considered to be stronger among the two algorithms. Since then, serious weaknesses have been found in both the algorithms. It is possible to break A5/2 in real-time with acipher text-only attack. In February 2008, a company named Pico Computing, Inc revealed its ability and plans to commercializeField Programmable Gate Array (FPGAs)that allows the A5/1 algorithm to be broken with arainbow table attack.Since the system supports multiple algorithms so operators may replace that cipher with a stronger one. (Jackson W, 2008)
SIM Cloning / Spoofing:
GSM uses a little plastic card containing subscriber's information called Subscriber Identity Module (SIM) for initiating and receiving calls from the mobile handset on a GSM network. But this SIM card can be cloned and used to make calls and impersonate customer's identification. So this would help the impersonator to send messages, make and receive calls using the customer's account. In another words, it is also called as SIM spoofing which manages to intercept the user's GSM signals. This threat may look simple from looking at the context. But when looking at the outcomes of it, it is a serious concern if the hackers are able to intercept most of the user's communication using some kind of hardware devices that facilitates them to achieve with at most ease. (Anonymous, 2010)
Mobile Tower 'Spoofing':
Normally in a mobile communication, the authentication level present between a mobile operator's tower and the user's cell phone is very low. So in this situation, users typically do not know which tower they are communicating with and this makes any eavesdropper or spoofer a better chance to carry out their spoof attacks. If they are successful, they can impersonate a mobile tower's reception and can communicate with the user's signal and act as the mobile tower itself. This is one of the typical and common methods of interception on a GSM network. Also it is easier nowadays to achieve this as the system requirements for this is as less that of a mobile phone and a personal computer with specific software. (Anonymous, 2010)
2.4 General Packet Radio Services (GPRS):
GPRS is a step between GSM and 3G cellular network used for high speed data transmission. It is a packet based technology which is available all the time which makes is possible for user to make a call and transfer any information at the same time. It enables the variety of packet transfer multimedia. It uses radio channel similar to voice calls of 200 KHz wide. GPRS supports leading internet communication protocol such as internet protocol and X.25. To operate over GSM cellular network GPRS enables any existing IP or X.25 application (Usha communication, 2000). In order to GPRS service to work operators has to install network overlays to allow migration to packet switching. The key elements of this are:
SGSN: It's a node between GSM infrastructure which allows transmission of packet data from the mobile station and keep track of the mobile (i.e. identify the mobile location) within the service area.
GGSN: It's a node that interfaces to public data network such as internet and X.25. To tunnel the protocol data units to SGSN's it maintains routine information.
Charging gateway: It's an interface between charging gateway functionalities and the billing system which makes long entry whenever there is a network activity such as data transfer, charging terms changing etc.
GPRS tunneling protocol: IP and X.25 packets should be encapsulated before being transferred between SGSN and GGSN.GTP operates over the top of standard TCP/IP to encapsulate IP or X.25. (Usha communication, 2000)The main benefit of GPRS is it reserves resources only when there is data to be sent. The main feature of this technology is the channel is used efficiently in such a way that there is a possibility that more than one use can share the channel at the same time. Another feature of this technology is if the data is being sent on various channels it provides more speed and efficiency.
GPRS has various advantages:
- Large amount of data can be transferred via internet using mobile phones.
- GPRS works indoors as well as outdoors like wherever there is no mobile network GPRS comes handy in such a situation.
- Acts as a modem when the GPRS enabled mobile is connected to laptops. (Sundaram, K. 2010)
As we have seen advantages of GPRS similarly GPRS has few disadvantages such as:
- It uses cellular network GSM band for data transfer, when connection is active, calls and other network related functions cannot be used.
- It is prioritized lower than speech so the quality of connection greatly varies if voice traffic is high.
- Speed of the connection drops logarithmically with distance from base station if the location is from the nearest GSM cell tower.
It is not suitable for real time data faster than 5-10 minutes for point to multi-point system. (Sundaram, K. 2010)
Like any other modern day technologies, GPRS too has some weaknesses in its security features. Some of them are listed below:
Signaling: In GPRS, the technology that is used for signaling exchange is System Signaling 7 (SS7) and it lacks some support when it comes to security protection. The SS7 technology does not support any security measure that provides node and message authentication, data confidentiality and message integrity due to the weakness present in the communication exchange in the GPRS Tunneling Protocol (GTP) and the GSN. So this makes the user data and the message across the GPRS architecture to be plain text and easily spoofed from outsiders from the network. This was not a great threat as till recently not much telecom operators were adapting it. This security weakness with the SS7 technology provokes a crucial threat to the GPRS network security, since it increases the probability of an adversary to get access to the network or a legitimate operator to act in a malicious manner. (Xenakis C, Merakos L, 2010)
Working of GPRS with GSM
GPRS is based on GSM communication so it complements circuit switched cellular phone connections, SMS (short message service) and Bluetooth. GPRS interfaces with GSM but it differs from GSM in various ways:
- Data speed is more due to high bandwidth.
- Continuous connection (Always online).
- New text and visual data and content services dude to high speed.
- It uses packet switching rather than circuit switching that means higher radio spectrum radio efficiency since network resources are used only when the data is transmitted.
- Supports communication protocol such as internet protocol and X.25.
- Additional components or protocol to GSM such as SGSN, GGSN.
- Available on all the devices such as laptops mobile phones etc which allows them to use WAP technology. (Usha communication, 2000)
2.5 Radio Frequency Identification Device (RFID)
RFID is the new chip based technology that is capable of capturing data between the RFID reader and the tag which can communicate remotely with a RFID reader. RFID technology is similar to the barcode system which is used now a day. The only difference between them is RFID eliminates the need of line of sight which barcode system totally depends on. It has three main parts:
- A scanning antenna
- A transceiver with a decoder to interpret a data.
- A transponder (RFID tag) that has been programmed with information.
The scanning antenna sends out short range of radio frequency signals. The radio frequency signal provides means of communication with the transponders along with RFID tags with energy to communicate. Since RFID tags does not use batteries so it last for long time may be for decade. When RFID tags passes through scanning antenna, it detects the activation signal from the antenna or in other terms it wakes up RFID chips and transmit the information to microchip picked up by scanning antenna.
There are two types of RFID. They are active RFID and passive RFID. They are fundamentally distinct technologies with different capabilities and do not provide complete asset management. Both the technologies use radio frequency to communicate between tags and the reader. Active RFID uses internal battery power but the passive RFID depends on the radio frequency energy transferred from reader to the tag and to the power tag. (Q.E.D. Systems, 2002)
Asset tracking using Active RFID
The active RFID activation antenna can be hidden anywhere like in ceiling rug etc. and the tag placed on the system is automatically identified at the exit and linked to the custodian. Unauthorized movements enable door locks and sound alarms.
Even desktops are secured with fixed RFID tagging since thieves can cut computer cables but with the active RFID tag equipped with a tamper wire an alarm is sent when the wire is damaged. Any high value asset can be protected with the RFID tags on (Axcess, 2005). There are various advantages of this technology:
- RFID tags are simple to install or inject thus keeping track of the asset.
- Does not require any line of sight, it communicates via radio waves.
- Damages to RFID are less likely to occur than the barcode system.
- Automatic scanning and data logging is possible without operator intervention.
- High level of data integrity. (Anonymous.2006)
- The technology is rugged and can be used in hostile environment.
- It can communicate data at distance as far as 300 feet.
- Capability to perform independent monitoring and control.
As there are advantages in this technology there are few disadvantages which need to be overcome:
- For short period, cost of diffusion and implementation for RFID can be higher.
- If reader and receiver are not properly aligned read rate can degrade.
- RFID technology ultimately uses software which allows every user will be identified using central data base which will be helpful for hacker to identify any information about the particular person or the asset.
- Active RFID cannot work without a battery power thus limiting the life of the tag.
- Active RFID is much more expensive than passive thus makes it difficult to afford for home users.
- Tags are physically larger which limits the application.
- Unread Tags: In case of multiple tags there is possibility that some tags are missed out.
- If a significant number of RFID's greater systems capabilities are implemented then the host system and infrastructure have a higher capital cost and complexity. (Anonymous.2006)
The above mentioned are disadvantages when using RFID technology. To lower the implementation cost depending on the type of the RFID tag you may be able to relocate, remove and reprogram them.
Now let us discuss some of the common security threats to the RFID tags:
Tag Cloning: This is one of the common threats that are faced in recent times. The RFID reader when contacting a RFID tagged device, the chip present in the tag emits a unique number called Electronic Product Code (EPC) which the reader can understand. This can be attacked from a spoofer and using the relevant technical information obtained, the person can clone the tag and make fake tags. This can be made to act as a genuine RFID tag reader in order to fake the service from a RFID chip. This is a break of Confidentiality.
Disruption of Service: As a result of Spoofing of RFID signals from either the reader or the tag, it is possible for an attacker to simply deny or disrupt the service requested or conveyed between a RFID tag and a RFID reader. This affects the availability of the RFID service.
Location Based Attacks: It can be otherwise described as man-in-the-middle relay attack. The attacker from a close proximity distance tries to relay messages between two RFID contacts and tries to make them that they are genuine communication with the concerned parties. Alternatively, an attacker can also use the same genuine signal and can change the communication between the machines. This indeed more or less a interception or just a denial of integrity.(Konidala M et al, 2010)
3. Theft detection system:
The development of wireless transmission and communication technologies has made wireless real time monitoring possible. This feature even got much better after invention of RFID and GPRS, by which people can monitor and dispatch mobile devices/assets or vehicle at any given time. The progress on technologies have provided favorable basis for the operation and management of remote assets. As a new kind of mobile packet data bearer service based on GSM, GPRS supplies end-to-end and wide area wireless IP connection. GPRS suits for interrupted, sudden data transmission or frequent, continuous data transmission in large quantities, which is ideal for mobile asset tracking (Dongsheng Z, 2009).
Initially, the vehicle carrying cash-box need to be monitored to detect theft, the security breach of this vehicle indicates that theft has occurred and can trigger the monitoring system through the GPRS technology and through smart messaging. Security breach of the vehicle can be identified by using active RFID technology. RFID is the method used to send information using radio waves. RFID system is consists of three elements: RFID readers, tags and backend database as already mentioned. If the RFID tag is tampered, a security message will be sent to the monitoring station through GSM/GPRS emitter. While vehicle wireless transmission system contains GPRS wireless network and vehicle-mounted embedded terminal which consists GPRS transmission module. The wireless transmission system in the monitoring station composed of lower computer's wireless transmission terminal and upper monitoring centre. The lower computer receives the location information from GPRS and then connects with distant monitoring centre to accept instructions and real time monitoring and transmission of the data are decided by the interaction with the monitoring centre (Dongsheng Z, 2009). The terminal which is in server mode installed in the monitoring centre waits for the connection signal from the wireless transmission terminal in the vehicle and it accepts or decodes the data packets as required. The wireless transmission terminal (GSM Terminal) in vehicle transmits the vehicle-mounted data to internet through the GPRS network, and then to monitoring system. The work of GSM terminal is to convert the received information from GPRS to SMS or IP packets which are able to be transmitted in the GPRS network.
4. Monitoring Cash-box:
Active RFID tag is attached near and inside the door of the cash box. Long distance RFID reader (can read ranges as far as 11 meters) is connected within the vehicle and remotely connected to the server in monitoring station through GPRS. Additionally the GSM terminal (stand alone system capable of SMS sending and receiving functions) is installed in the vehicle to alert monitoring station in the case of theft or any abnormal situation. Typically GSM terminal will come with a RS232 connector to external terminal equipment (RFID reader) and the SIM cardholder. The reader scans the tag at regular time intervals (say 5 sec). If the cash box is taken out of the range of the reader then the reader cannot detect the signals from the tag, then alarm system gets activated drawing attention. Simultaneously the monitoring system will be alerted within seconds through sending smart message through GSM terminal to monitoring staff (Kyun Ng C, 2008). Smart messaging is a special type of functional short message which makes it possible to easily identify the action to be taken to the receiver. When the GSM Terminal sends out an SMS, the short message service centre (SMSC) will relay this data to the SMS-gateway mobile switching centre (SMS-GMSC).The SMS-GMSC will then access the home location register (HLR), search to locate the cellular phone address at the end point, and send route information to the mobile switching centre (MSC).After receiving this data, the MSC will determine which SMSC to contact for this end point.
Secure Tracking System for Cashboxes 2010
With the help of GMS roaming protocol, the SMS GMSC locates MSC of message receiver based on the information received by Home Location Register (HLR) and forwards the message to MSC. MSC then passes the message to a SMSC and then to the reverse steps is taken to deliver the message to the destination. Table briefly explains the commands used to send or receive SMS with GSM modem (Govindan G et al, 2010).
Secure Tracking System for Cashboxes 2010
5. Tracking System:
EGNOS (European Geostationary Navigation Overlay Service) is Europe's wide area differential augmentation system for GNSS (Global Navigational Satellite Systems) EGNOSdata are made available to the user via terrestrial networks to fill the geostationary coverage gaps due to urban environment and high latitudes. This satisfies the needs for the highly accurate and guaranteed navigation services. Cash-box tracking sector is one of the major potential markets for GNSS applications. Satellite navigation receiver (explained further) is installed in the cash-box as a key tool. EGNOS and Galileo will provide better accuracy than of GPS and will make available the data integrity information to certify and guarantee the service (Teotino D et al, 2005).
Three major elements can be identified: the Cash-box segment, the space segment and the ground segment.
- The Cash-box Segment: this consists of a unit installed on board and used for positioning as well as to exchange data with the service control centre. This terminal is having/should be compatible with GPRS, GPS/EGNOS, Bluetooth, Smart MMI and Thin DB /Maps (Open GIS platforms).
- The Space Segment: based on EGNOS and Galileo this provides the signal-in-space (SIS) used by the on-board unit to calculate the positioning to receive the integrity messages as well as the corrections.
- The Ground Segment: Consists of Service Control Centre (SCC), Service Provider (SP), Communication Network. The link between the SCC and the Cash-box (OBU) is based on terrestrial mobile communication (GPRS). This maintains the communication among the SCC and the cash-box for the data exchange (Teotino D et al, 2005).
This system corresponds to increased accuracy, availability, integrity and certified services.
The tracking system is built on the INStANT Infrastructure Technology developed in the frame of the 5th framework programme of EC.
The core part of the system is represented by the OBU (on board unit), SCC and OBSs (On-board Sensors). OBS include the sensors to evaluate the position. The SCC works as intermediate between the OBU and the SPs providing information needed for mapping the cash-box. The SCC also interacts with the External Data Providers for general information data, like metrological data, corrections from EGNOS (VeRT, 2010). The receiver is designed by including the below modules:
Secure Tracking System for Cashboxes 2010
- Accuracy: 1-3 m
- Antenna: Built-in into the device
- Size: 5"X2"X0.5"
- Modem Type: GSM/GPRS Integrated
- Receiver type: GPS/EGNOS (Tracking and Navigating function)
- Temperature: -20oC to 55oC
- Case: ABS Plastic
Secure Tracking System for Cashboxes 2010
Service Control Centre (SCC) consists and responsible for Web services: this includes a device mapper capability, to allow the connection to a broad range of mobile devices such as OBU. Secure Messaging, Command and Control: to allow the SP to manage real-time operations and partial failures of the system. Asset management, GIS: contain routes, Geo-referenced real time data with facilities for scoped location based services and digital maps of areas are used. Cash-box access control service: is the core part of the Service Manager, this makes the cash-box to be securely accessed by external authorized monitoring centre (VeRT, 2010).
For the communication purposes, GPRS seems certainly the most feasible solution for this system. GPRS adapts new physical channels and mapping into physical resources. The radio link protocol provides a reliable link, while MAC protocols controls access with signaling procedures for radio channel and the mapping of Link Layer Control (LLC) frames onto the GSM channels. As described SGSN represents the packet world and Mobile Switching Centre represents for circuit world. SGSN performs mobility management (area update, mobile stating paging) as well as security tasks (Teotino D et al, 2005).
To mitigate the current RFID threats we can use encrypted RFID which is new technology being proposed.
Hash chain based protocol for privacy protection, forward security, and tag to server authentication can be implemented in RFID readers to address the integrity issues.
Implementing IPSec between our system and the access point, traffic rate limiting and GTP stateful inspection can mitigate the significant number of threats on roaming network.
EGNOS is used for improving GPS availability and precise locating technique. Further EGNOS TRAN can be used to enhance the performance and security issues which are not found in EGNOS.
To address the jamming issues in the GPS, Controlled Reception Pattern Antenna is used to determine the direction of jamming source. Therefore by modifying its antenna reception pattern which ignores the signal from that direction.
Pre-authentication information in the GSM channel assignment protocol is used to add resistance of DOS attacks.
Active RFID equipment- $1 to $100
GSM modem- $150
GPRS Transmitter- $1-100
This assignment has demonstrated integrated design of the cashbox security tracking system with RFID, GPS/EGNOS, GPRS with SMS messaging feature. Basically the RFID reader is functioning as tamper detection mechanism to detect any abnormal situation. The GPRS transmitter is activated successfully to trigger the monitoring system. Monitoring system works with GPS/EGNOS to trace the cash box. GPRS works as communication framework for the entire system. Furthermore to enhance the system the countermeasures are considered and can be implemented for the reliable, robust, and secure tracking system.
Anonymous, (2006)RFID Technology in Transit. Available: http://rfidintro.wetpaint.com/. Last accessed 20 March 2010.
Anonymous. (2008)What is GPRS?. Available: http://www.alphamicro.net/white_paper~id~1.asp. Last accessed: 19 March 2008.
Anonymous. (2010),GSM Security. Available: http://www.cryptophone.com.au/GSMSecurity.htm Last accessed: 17 May 2010.
Anonymous (2010),GPS Vulnerability - Information for CIOs. Available: http://www.ag.gov.au/agd/WWW/rwpattach.nsf/VAP/(930C12A9101F61D43493D 44C70E84EAA)~GNSS+Advice+to+CIOs+with+CEO+ref.doc.pdf/$file/GNSS+Advice+to+ CIOs+with+CEO+ref.doc.pdf Last accessed 17 May 2010.
Axcess, (2005)Active Radio Frequency Identification (RFID) Powers Productivity and Protection in the Enterprise. Available: http://wp.bitpipe.com/resource/org_1104422963_695/ActiveRFIDPowers Productivity. pdf?site_cd=vnu. Last accessed: 21 March 2010.
BONNET C, (2004) "EGNOS broadcasting over RDS" Available at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1356363 [Date accessed 20 Mar 2010].
Dongsheng Z, (2009) "Research and Design on Vehicle-mounted Wireless Transmission Terminal" Capital Normal University, Available at: http://ieeexplore.ieee.org/search/srchabstract.jsp?tp=&arnumber=5384581&queryText%3DResearch+and+Design+on+Vehicle-mounted+Wireless+Transmission+Terminal%26openedRefinements%3D*%26searchField%3DSearch+All [Date Accessed: March 20,2010].
Garmin. (2010).GPS.Available: http://www8.garmin.com/aboutGPS/. Last accessed 19 March 2008.
Govindan G et al, (2010) "Real time Security Management using RFID, Biometric and Smart Messages" Available at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5276898 [Date Accessed: 20 Mar2010].
Jackson W (2008),Cracking GSM calls, made affordable and easy. Available: http://gcn.com/articles/2008/02/20/cracking-gsm-calls-made-affordable-and-easy.aspx Last Accessed: 17 May 2010.
Konidala M et al,(2010). Open Issues in RFID. Last accessed: 17 May 2010
Kyun Ng C, (2008) "Theft Prevention using Wireless Security System (WSS)" Department of Computer and Communication Systems Engineering, Faculty of Engineering, University Putra Malaysia. Available at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4897429 [Date Accessed: 20 Mar 2010].
Linsell, P. (2002).Advantages of GPS technology.Available: http://www.helium.com/items/798584-advantages-of-gps-technology. Last accessed 21 March 2010.
Palmer J. (2010), Sat-nav systems under growing threat from 'jammers'. Available: http://news.bbc.co.uk/1/hi/sci/tech/8533157.stm Last accessed: 17 May 2010
Q.E.D. Systems, (2002)Part 1: Active and Passive RFID: Two Distinct, But Complementary, Technologies for Real-Time Supply Chain Visibility. Available: http://www.autoid.org/2002_Documents/sc31_wg4/docs_501-520/520_18000-7_WhitePaper.pdf. Last accessed: 20 March 2010.
Sundaram, K. (2010).The Pros and Cons of GPRS Technology.Available: http://www.brighthub.com/mobile/symbian-platform/articles/16995.aspx. Last accessed: 19 March 2008.
Teotino D, (2005), "System Architecture of the Vehicular Remote Tolling (VeRT) Project", Available at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1559477 [Date Accessed: 20 Mar 2010].
Usha communication. (2000).GPRS.Available: http://www.mobilein.com/GPRS.pdf. Last accessed 20 March 2010.
VeRT, (2010), "Vehicular Remote Tolling", Available at: http://www.instant-olympic.com/Dissemination/VeRT(Abstract).pdf [Date Accessed: 20 Mar 2010].