Bluetooth usage with Architecture view & security measures

Transcription

1 Bluetooth usage with Architecture view & security measures Savan K. Patel Assi.Professor AMPICS Dept Ganpat University Kherva, Gujarat, India Hiral R.Patel Assi.Professor Department of CS, Ganpat University Kherva, Gujarat, India Ravi S.Patel Assi.Professor AMPICS Dept, Ganpat University Kherva, Gujarat, India ABSTRACT The Bluetooth wireless technology was created to solve a simple problem: replace the cables used on mobile devices with radio frequency waves. The technology encompasses a simple low-cost, low power, Global radio system for integration into mobile devices. Such devices can form a quick ad-hoc secure "piconet" and communicate among the connected devices. This technology creates many useful mobile usage models because the connections can occur while mobile devices are being carried in pockets and briefcases (therefore, there are no line-of-sight restrictions). This paper Provides a brief description of some of these usage models and explains how the Bluetooth architecture is optimized to enable them. It also represents how Bluetooth works? How it will be operated? & how security measures provided? Today the Bluetooth technology is the only specification targeted at this new market of cable replacement. Even the IEEE organization has recognized the need for wireless cable replacement Technology and started the development of the working group that focuses on this market (they call it Wireless Personal Area Networks). This specification is based on the Bluetooth technology! Keywords Bluetooth, Piconet, IEEE, , PAN, Wireless, Ad-hoc network, Data Access Points, Cable Replacement 1. INTRODUCTION Bluetooth is a specification for the use of low-power radio communications to wirelessly link phones, computers and other network devices over short distances. The Bluetooth technology was developed by members of a Special Interest Group (SIG). The participating companies agree not to charge royalties on any Intellectual Property (IP) necessary to implement the technology. The name Bluetooth is borrowed from Harald Bluetooth, a king in Denmark more than 1,000 years ago. Bluetooth technology was designed primarily to support simple wireless networking of personal consumer devices and peripherals, including cell phones, PDAs, and wireless headsets. Wireless signals transmitted with Bluetooth cover short distances, typically up to 30 feet (10 meters). Bluetooth devices generally communicate at less than 1 Mbps. Bluetooth networks feature a dynamic topology called a piconet or PAN. Piconets contain a minimum of two and a maximum of eight Bluetooth peer devices. Devices communicate using protocols that are part of the Bluetooth Specification. Definitions for multiple versions of the Bluetooth specification exist including versions 1.1, 1.2 and 2.0. The Bluetooth technology was developed to provide a wireless interconnect between small mobile devices and their peripherals. Target markets were the mobile computer, the mobile phone, small personal digital assistants and peripherals.although the Bluetooth standard utilizes the same 2.4 Ghz range as b and g, Bluetooth technology is not a suitable Wi-Fi replacement. Compared to Wi-Fi, Bluetooth networking is much slower, a bit more limited in range, and supports many fewer devices. As is true for Wi-Fi and other wireless technologies today, concerns with Bluetooth technology include security and interoperability with other networking standards. Bluetooth was ratified as IEEE [1] 2. USAGE MODEL While the Bluetooth usage model is based on connecting devices together, it is focused on three broad categories: voice/data access points, peripheral interconnects, and Personal Area Networking (PAN). [10] 2.1 Voice/data access points Voice/data access points are one of the key initial usage models and involve connecting a computing device to a communicating device via a secure wireless link (see Figure 1). For example, a mobile computer equipped with ISSN: Page 30

2 Bluetooth technology could link to a mobile phone that uses Bluetooth technology to connect to the Internet to access . The mobile phone acts as a personal access point. Even more ideal, the notebook can connect to the Internet while the cell phone is being carried in a briefcase or purse. [10] devices can be used in multiple markets. Figure 1: Voice/data access points [2] The Bluetooth usage model also envisions public data access points in the future. Imagine the current dataequipped pay phones in airports being upgraded with Bluetooth modems. This would allow any mobile device equipped with Bluetooth technology to easily connect to the Internet while located within ten meters of that access point. These access points could, of course, support much higher data rates than today's modems, as public spaces could connect a variety of private Bluetooth access points via a LAN that is routed to the Internet over a DSL line, allowing each access point a private 1Mbps connection to the Internet. [10] 2.2 Peripheral interconnects The second category of uses, peripheral interconnects, involves connecting other devices together as shown in Figure 2. Imagine standard keyboards, mice, and joysticks that work over a wireless link. The Bluetooth link is built into the mobile computer; therefore, the cost of the peripheral device is less because an access point is not needed. Additionally, many of these Figure 2: Peripheral interconnects [2] For example, a Bluetooth headset used in the office could be connected to a Bluetooth access point that provides access to the office phone and multi-media functions of the mobile computer. When mobile, the same headset could be used to interface with the cellular phone (which can now remain in a briefcase or purse). 2.3 Personal Area Networking (PAN) The last usage model, Personal Area Networking (PAN), focuses on the ad-hoc formation and breakdown of personal networks (see Figure 3). Imagine meeting someone in an airport and quickly and securely exchanging documents by establishing a private piconet. Figure 3: PAN [2] In the future, Bluetooth kiosks could provide access to electronic media that could be quickly downloaded for later access on the mobile device. 3. ARCHITECTURE OVERVIEW Bluetooth Communications occurs between a master radio and a slave radio. Bluetooth radios are symmetric in that ISSN: Page 31

3 the same device may operate as a master and also the slave. Each radio has a 48-bit unique device address (BD_ADDR) that is fixed. Two or more radio devices together form adhoc networks called Pico nets. [8] All units within a piconet share the same channel. Each piconet has one master device and one or more slaves. There may be up to seven active slaves at a time within a piconet. Thus, each active device within a piconet is identifiable by a 3-bit active device address. Inactive slaves in unconnected modes may continue to reside within the piconet. The Bluetooth technology is divided into two specifications: the core and the profile specifications. The core specification discusses how the technology works, while the profile specification focuses on how to build interoperating devices using the core technologies. This paper deals with the core Technology, as illustrated in Figure 4, and focuses on the lower layers of the Bluetooth architecture (up to the link manager).[8] Figure 4: Bluetooth Architecture [2] 3.1 Radio Frequency Layer The Bluetooth air interface is based on a nominal antenna power of 0dBm (1mW) with extensions for operating at up to 20dBm (100mW) worldwide. The air interface complies with most countries' ISM band rules up to 20dBm (America, Europe, and Japan). The radio uses Frequency Hopping to spread the energy across the ISM spectrum in 79 hops displaced by 1MHz, starting at 2.402GHz and stopping at 2.480GHz. Currently, the SIG is working to harmonize this 79-channel radio to work Globally and has instigated changes within Japan, Spain, and other countries. [7] The nominal link range is 10 centimeters to 10 meters, but can be extended to more than 100 meters by increasing the transmit power (using the 20dBm option).[7] 3.2 Bluetooth Base band As mentioned previously, the basic radio is a hybrid spread spectrum radio. Typically, the radio operates in a frequency-hopping manner in which the 2.4GHz ISM band is broken into 79 1MHz channels that the radio randomly hops through while transmitting and receiving data. A piconet is formed when one Bluetooth radio connects to another Bluetooth radio. Both radios then hop together through the 79 channels. The Bluetooth radio system supports a large number of piconets by providing each piconet with its own set of random hopping patterns. Occasionally, piconets will end up on the same channel. When this occurs, the radios will hop to a free channel and the data are retransmitted (if lost). The Bluetooth frame consists of a transmit packet followed by a receive packet. Each packet can be composed of multiple slots (1, 3, or 5) of 625us. 3.3 Network Topology Figure 5 illustrates a typical piconet with each small bubble (M, S, P, or Sb) representing a Bluetooth radio. Bluetooth radios connect to each other in piconets, which are formed by a master radio simultaneously connecting up to seven slave radios. The Bluetooth radios are symmetric in that any Bluetooth radio can become a master or slave radio, and the piconet configuration is determined at the time of formation. Figure 5: Network topology [2] ISSN: Page 32

4 Typically, the connecting radio will become the master; however, a "master/slave swap" function allows the roles to be reversed. (A device can only be a master in one piconet though.) 4. HOW BLUETOOTH OPERATES? Bluetooth networking transmits data via low-power radio waves. It communicates on a frequency of 2.45 gigahertz (actually between GHz and GHz, to be exact). This frequency band has been set aside by international agreement for the use of industrial, scientific and medical devices (ISM). [13] A number of devices that you may already use take advantage of this same radio-frequency band. Baby monitors, garage-door openers and the newest generation of cordless phones all make use of frequencies in the ISM band. Making sure that Bluetooth and these other devices don't interfere with one another has been a crucial part of the design process. One of the ways Bluetooth devices avoid interfering with other systems is by sending out very weak signals of about 1 mill watt. By comparison, the most powerful cell phones can transmit a signal of 3 watts. [11] The low power limits the range of a Bluetooth device to about 10 meters (32 feet), cutting the chances of interference between your computer system and your portable telephone or television. Even with the low power, Bluetooth doesn't require line of sight between communicating devices. The walls in your house won't stop a Bluetooth signal, making the standard useful for controlling several devices in different rooms. Bluetooth can connect up to eight devices simultaneously. With all of those devices in the same 10-meter (32-foot) radius, you might think they'd interfere with one another, but it's unlikely. Bluetooth uses a technique called spreadspectrum frequency hopping that makes it rare for more than one device to be transmitting on the same frequency at the same time. In this technique, a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis. [3, 9, 11] 5. HOW BLUETOOTH CREATES A CONNECTION? Bluetooth takes small-area networking to the next level by removing the need for user intervention and keeping transmission power extremely low to save battery power. Picture this: You're on your Bluetooth-enabled cell phone, standing outside the door to your house. You tell the person on the other end of the line to call you back in five minutes so you can get in the house and put your stuff away. As soon as you walk in the house, the map you received on your cell phone from your car's Bluetooth-enabled GPS system is automatically sent to your Bluetooth-enabled computer, because your cell phone picked up a Bluetooth signal from your PC and automatically sent the data you designated for transfer. Five minutes later, when your friend calls you back, your Bluetooth-enabled home phone rings instead of your cell phone. The person called the same number, but your home phone picked up the Bluetooth signal from your cell phone and automatically rerouted the call because it realized you were home. And each transmission signal to and from your cell phone consumes just 1 mill watt of power, so your cell phone charge is virtually unaffected by all of this activity. Bluetooth is essentially a networking standard that works at two levels: It provides agreement at the physical level -- Bluetooth is a radio-frequency standard. It provides agreement at the protocol level, where products have to agree on when bits are sent, how many will be sent at a time, and how the parties in a conversation can be sure that the message received is the same as the message sent. Bluetooth is intended to get around the problems that come with infrared systems. The older Bluetooth 1.0 standard has a maximum transfer speed of 1 megabit per second (Mbps), while Bluetooth 2.0 can manage up to 3 Mbps. Bluetooth 2.0 is backward-compatible with 1.0 devices. [9, 12] 6. BLUETOOTH SECURITY In any wireless networking setup, security is a concern. Devices can easily grab radio waves out of the air, so people who send sensitive information over a wireless connection need to take precautions to make sure those signals aren't intercepted. Bluetooth technology is no different -- it's wireless and therefore susceptible to spying ISSN: Page 33

5 and remote access, just like Wi-Fi is susceptible if the network isn't secure. With Bluetooth, though, the automatic nature of the connection, which is a huge benefit in terms of time and effort, is also a benefit to people looking to send you data without your permission. Bluetooth offers several security modes, and device manufacturers determine which mode to include in a Bluetooth-enabled gadget. In almost all cases, Bluetooth users can establish "trusted devices" that can exchange data without asking permission. When any other device tries to establish a connection to the user's gadget, the user has to decide to allow it. Service-level security and device-level security work together to protect Bluetooth devices from unauthorized data transmission. Security methods include authorization and identification procedures that limit the use of Bluetooth services to the registered user and require that users make a conscious decision to open a file or accept a data transfer. As long as these measures are enabled on the user's phone or other device, unauthorized access is unlikely. [13] A user can also simply switch his Bluetooth mode to "non-discoverable" and avoid connecting with other Bluetooth devices entirely. If a user makes use of the Bluetooth network primarily for synching devices at home, this might be a good way to avoid any chance of a security breach while in public. Other problems like "blue jacking," "blue bugging" and "Car Whisperer" have turned up as Bluetooth-specific security issues. Blue jacking involves Bluetooth users sending a business card (just a text message, really) to other Bluetooth users within a 10-meter (32-foot) radius. If the user doesn't realize what the message is, he might allow the contact to be added to his address book, and the contact can send him messages that might be automatically opened because they're coming from a known contact. Blue bugging is more of a problem, because it allows hackers to remotely access a user's phone and use its features, including placing calls and sending text messages, and the user doesn't realize its happening. The Car Whisperer is a piece of software that allows hackers to send audio to and receive audio from a Bluetooth-enabled car stereo. Like a computer security hole, these vulnerabilities are an inevitable result of technological innovation, and device manufacturers are releasing firmware upgrades that address new problems as they arise. [12] 6.1 Link layer security architecture The way that the Bluetooth radio system is used in mobile devices and the type of data carried on these devices (e.g., a corporate mobile computer) makes security an extremely important factor. While most wireless systems will claim that being a spread spectrum radio provides security, the volumes projected for Bluetooth radios eliminate this barrier. As such, link layer and application layer security are part of the basic Bluetooth radio requirements. Figure 6: Network topology [2] At a link layer, the Bluetooth radio system provides Authentication, Encryption, and Key Management of the various keys involved. Authentication involves the user providing a Personal Identification Number (PIN) that is translated into a 128-bit link key that can be authenticated in a one- or two-way direction. Once the radios are authenticated, the link can be encrypted at various key lengths (up to 128-bits in 8-bit key increments). The link layer security architecture provides a number of authentication schemes and a flexible encryption scheme that allows radios to negotiate for key length. This is important, as radios from different countries will be talking to each other. ISSN: Page 34

6 The Bluetooth security architecture relies on PIN codes for establishing trusted relationships between devices. While not practical to go through all the combinations of uses of PIN codes, it should be noted that once a trusted pairing is established between devices, these codes can be stored within the device to allow more automatic/simple connections. The key to Bluetooth simplicity will be establishing the trusted relationship between commonly used devices. For random ad-hoc connections that require authenticated connections (such as ensuring you are connecting to who you think you are connecting to, something that is not always obvious with invisible radio waves), PINs would have to be exchanged (depending on how the devices are configured). 7. CONCLUSION Bluetooth is a radio system designed for connecting a variety of mobile devices in a secure ad-hoc fashion. Much thought has gone into developing a radio system that provides interoperability between different device types while also meeting the requirements of mobile users. This paper covered a small aspect of the Bluetooth radio system, the lower layers of the Bluetooth radio stack. In this paper main focus o Bluetooth architecture & its security measures. The Bluetooth radio system provides Authentication, Encryption, and Key Management of the various keys involved. 8. REFERENCE [7]. Bluetooth Architecture overview, james Kardach, mobile computing group, Intel Corporation [8]. Bluetooth Technology, Jennifer Carter IET 680 [9]. Bluetooth Technology, shweta khetarpal, May 2004 [10]. Bluetooth technology Aboon to wireless Communication, Nitesh Rjal, Gopal Shah NCIT [11]. An expanded Bluetooth network-a solution to the Short range Bluetooth communication, Preetha K G, Dept IT. [12]. Bluetooth Wireless, Kyle Miller [13]. Bluetooth, Nick Greaner [1]. an Article on Bluetooth Wireless/Networking By: Bradley Mitchell, Available At: [2]. an Article on Bluetooth Architecture Overview By: James Kardach Mobile Computing Group, Intel Corporation, Available At: [3]. an Article on How Bluetooth Works By: Curt Franklin, Available At: [4]. an Article on Bluetooth Security By: Julia Layton, Available At: [5]. [6]. ISSN: Page 35