Introduction

A typical Bluetooth mobile phone headsetBluetooth is a radio standard primarily designed for low power consumption, with a short range (power class dependent: 10 centimetres, 10 metres, 100 metres or up to 400 metres , ) and with a low-cost transceiver microchip in each device. Bluetooth lets these devices talk to each other when they come in range, even if they are not in the same room, as long as they are within up to 100 metres (328 feet) of each other, dependent on the power class of the product. Products are available in one of three power classes: Class 1 (100 mW) [still readily available]: It has the longest range at up to 100 metres (328 ft). Class 2 (2.5 mW) [most common]: It allows a quoted transmission distance of 10 metres (33 ft). Class 3 (1 mW) [rare]: It allows transmission of 10 cm (3.9 in), with a maximum of 1 metre (3.3 ft).

Bluetooth applications

A Bluetooth mouseWireless Networking between desktops and laptops, or desktops in a confined space and where little bandwidth is required Bluetooth peripherals such as printers, mice and keyboards Bluetooth cell phones have been sold in large numbers, and are able to connect to computers, Personal digital assistants (PDAs) and, specifically, to handsfree devices.

*The standard also includes support for more powerful, longer-range devices suitable for constructing wireless LANs. Transfer of files (images, mp3s, etc) between mobile phones, Personal digital assistants (PDAs) and computers via OBEX Certain mp3 players and Digital Cameras to transfer files to and from computers Bluetooth headsets for mobile phones & Smartphones Some testing equipment is bluetooth enabled Medical applications - Advanced Medical Electronics

*Corporation is working on several devices Certain GPS receivers transfer NMEA data via Bluetooth Bluetooth car kits - Acura was the first motor vehicle manufacturer to install handsfree Bluetooth technology in the 2004 Acura TL. Later on BMW added it as an option on its 3 Series, 5 Series, 7 Series and X5 vehicles. Since then, other manufacturers have followed suit, with many vehicles, including the 2004 Toyota Prius and the 2004 Lexus LS 430. The Bluetooth car kits allow users with Bluetooth-equipped cell phones to make use of some of the phone's features, such as making calls, while the phone itself can be left in a suitcase or in the boot/trunk, for instance. Companies like Parrot or Motorola manufacture Bluetooth hands-free car kits for well-known brand car manufacturers. Certain data logging equipment transmits data to a computer via Bluetooth. For remote controls where infrared was traditionally used.

*Hearing aids - Starkey Laboratories have created a device to plug into some hearing aids Specifications and Features The Bluetooth specification was first developed by Ericsson, and was later formalized by the Bluetooth Special Interest Group (SIG). The SIG was formally announced on May 20, 1999. It was established by Sony Ericsson, IBM, Intel, Toshiba and Nokia, and later joined by many other companies as Associate or Adopter members.

Bluetooth is also IEEE 802.15.1. Bluetooth 1.0 and 1.0B Versions 1.0 and 1.0B had numerous problems and the various manufacturers had great difficulties in making their products interoperable. 1.0 and 1.0B also had mandatory Bluetooth Hardware Device Address (BD_ADDR) transmission in the handshaking process, rendering anonymity impossible at a protocol level, which was a major set back for services planned to be used in Bluetooth environments, such as Consumerium.

Bluetooth 1.1

In version 1.1: many errata found in the 1.0B specifications were fixed. There was added support for non-encrypted channels. Received Signal Strength Indicator (RSSI) Bluetooth 1.2 This version is backwards compatible with 1.1 and the major enhancements include Adaptive Frequency Hopping (AFH), which improves resistance to radio frequency interference by avoiding using crowded frequencies in the hopping sequence Higher transmission speeds in practice extended Synchronous Connections (eSCO), which improves voice quality of audio links by allowing retransmissions of corrupted packets. Host Controller Interface (HCI) support for 3-wire UART HCI access to timing information for Bluetooth applications.

Bluetooth 2.0

This version is backwards compatible with 1.x. The main enhancement is the introduction of Enhanced Data Rate (EDR) of 2.1 Mbit/s. This has the following effects (Bluetooth SIG, 2004): 3 times faster transmission speed (up to 10 times in certain cases). Lower power consumption through reduced duty cycle. Simplification of multi-link scenarios due to more available bandwidth. Further improved BER (Bit error rate) performance.

Technical information Communication & Connection

A Bluetooth device playing the role of the "master" can communicate with up to 7 devices playing the role of the "slave". This network of "group of up to 8 devices" (1 master + 7 slaves) is called a piconet. At any given time, data can be transferred between the master and 1 slave; but the master switches rapidly from slave to slave in a round-robin fashion. (Simultaneous transmission from the master to multiple slaves is possible, but not used much in practice). Either device may switch the master/slave role at any time. Bluetooth specification allows connecting 2 or more piconets together to form a scatternet, with some devices acting as a bridge by simultaneously playing the master role in one piconet and the slave role in another piconet. 

Setting up connections

Any Bluetooth device will transmit the following sets of information on demand

*Device Name

*Device Class

*List of services

*Technical information eg: device features, manufacturer, Bluetooth specification, clock offset

Any device may perform an "inquiry" to find other devices to which to connect, and any device can be configured to respond to such inquiries. However if the device trying to connect knows the address of the device it will always respond to direct connection requests and will transmit the information shown in the list above if requested for it. Use of the device's services however may require pairing or its owner to accept but the connection itself can be started by any device and be held until it goes out of range. Some devices can only be connected to one device at a time and connecting to them will prevent them from connecting to other devices and showing up in inquiries until they disconnect the other device. Every device has a unique 48-bit address. However these addresses are generally not shown in inquiries and instead friendly "Bluetooth names" are used which can be set by the user, and will appear when another user scans for devices and in lists of paired devices. Most phones have the Bluetooth name set to the manufacturer and model of the phone by default. Most phones and laptops will only show the Bluetooth names and special programs are required to get additional information about remote devices. This can get confusing with activities such as Bluejacking as there could be several phones in range named "T610" for example. On Nokia phones the Bluetooth address may be found by entering "*#2820#". On computers running Linux the address and class of a USB Bluetooth dongle may be found by entering "hciconfig hci0 class" as root ("hci0" may need to be replaced by another device name). Every device also has a 24-bit class identifier. This provides information on what kind of a device it is (Phone, Smartphone, Computer, Headset, etc), which will also be transmitted when other devices perform an inquiry. On some phones this information is translated into a little icon displayed beside the device's name. Bluetooth devices will also transmit a list of services if requested by another device; this also includes some extra information such as the name of the service and what channel it is on. These channels are virtual and have nothing to do with the frequency of the transmission, much like TCP ports. A device can therefore have multiple identical services. Pairing Pairs of devices may establish a trusted relationship by learning (by user input) a shared secret known as a "passkey". A device that wants to communicate only with a trusted device can cryptographically authenticate the identity of the other device. Trusted devices may also encrypt the data that they exchange over the air so that no one can listen in. The encryption can however be turned off and passkeys are stored on the device's file system and not the Bluetooth chip itself. Since the Bluetooth address is permanent a pairing will be preserved even if the Bluetooth name is changed. Pairs can be deleted at any time by either device. Devices will generally require pairing or will prompt the owner before it allows a remote device to use any or most of its services. Some devices such as Sony Ericsson phones will usually accept OBEX business cards and notes without any pairing or prompts. Certain printers and access points will allow any device to use its services by default much like unsecured Wi-Fi networks. Air interface The protocol operates in the license-free ISM band at 2.45 GHz. In order to avoid interfering with other protocols which use the 2.45 GHz band, the Bluetooth protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Implementations with versions 1.1 and 1.2 reach speeds of 723.1 kbit/s. Version 2.0 implementations feature Bluetooth Enhanced Data Rate (EDR), and thus reach 2.1 Mbit/s. Technically version 2.0 devices have a higher power consumption, but the three times faster rate reduces the transmission times, effectively reducing consumption to half that of 1.x devices (assuming equal traffic load).

Bluetooth differs from Wi-Fi in that the latter provides higher throughput and covers greater distances but requires more expensive hardware and higher power consumption. They use the same frequency range, but employ different multiplexing schemes. While Bluetooth is a cable replacement for a variety of applications, Wi-Fi is a cable replacement only for local area network access. A glib summary is that Bluetooth is wireless USB whereas Wi-Fi is wireless Ethernet, both operating at much lower bandwidth than the cable systems they are trying to replace. Many USB Bluetooth adapters are available, some of which also include an IrDA adapter.

Security

Security measures Bluetooth uses the SAFER+ algorithm for authentication and key generation. The E0 stream cipher is used for encrypting packets. This makes eavesdropping on bluetooth-enabled devices more difficult.

In November 2003, Ben and Adam Laurie from A.L. Digital Ltd. discovered that serious flaws in Bluetooth security may lead to disclosure of personal data (see http://bluestumbler.org). It should be noted however that the reported security problems concerned some poor implementations of Bluetooth, rather than the protocol itself. In a subsequent experiment, Martin Herfurt from the trifinite.group was able to do a field-trial at the CeBIT fairgrounds showing the importance of the problem to the world. A new attack called BlueBug was used for this experiment. 2004: In April 2004, security consultants @Stake revealed a security flaw that makes it possible to crack into conversations on Bluetooth based wireless headsets by reverse engineering the PIN. This is one of a number of concerns that have been raised over the security of Bluetooth communications. In 2004 the first purported virus using Bluetooth to spread itself among mobile phones appeared for the Symbian OS. The virus was first described by Kaspersky Labs and requires users to confirm the installation of unknown software before it can propagate. Note: the virus was written as a proof-of-concept by a group of virus writers known as 29a and sent to anti-virus groups. Thus it should be regarded as a potential (but NOT real) security threat of Bluetooth or Symbian OS as the virus has never spread in the wild. In August 2004, a world-record-setting experiment (see also Bluetooth sniping) showed that the range of class 2 Bluetooth radios could be extended to 1.78 km (1.08 mile) with directional antennas. This poses a potential security threat as it enables attackers to access vulnerable Bluetooth-devices from a distance beyond expectation. However such experiments will not work using signal amplifiers as the attacker must also be able to receive information from its victim in order to set up a connection. No attack can be made against a bluetooth device unless the attacker knows its Bluetooth address and which channels to transmit on.

In June 2005 Yaniv Shaked and Avishai Wool published the paper "Cracking the Bluetooth PIN1", which shows both passive and active methods for obtaining the PIN for a Bluetooth Link. The passive attack would allow a suitably equipped attacker to eavesdrop on communications and spoof if they were present at the time of initial pairing. The active method makes use of a specially constructed message that must be inserted at a specific point in the protocol, to make the master and slave repeat the pairing process. After that the first method may be used to crack the PIN. This attack's major weakness is that it requires the user of the devices under attack to re-enter their PIN during the attack when their device prompts them to. Also, this active attack will most likely require custom hardware, as most commercially available Bluetooth Devices are not capable of the timing necessary. In August 2005, police in Cambridgeshire, England, issued warnings about thieves using Bluetooth-enabled phones to track other devices left in cars. Police are advising users to ensure any mobile networking connections are de-activated if laptops and other devices are left in this way. However the best way is to not leave any valuable devices in cars. They should be kept with you.