From Wikipedia, the free encyclopedia
- This article is about an electronic device. For Harald Bluetooth Gormson, see Harald I of Denmark.
Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras and video game consoles via a secure, globally unlicensed short-range radio frequency.
Bluetooth is a radio standard and communications protocol primarily designed for low power consumption, with a short range (power class dependent: 1 metre, 10 metres, 100 metres) based around low-cost transceiver microchips in each device.
Bluetooth lets these devices communicate with each other when they are in range. The devices use a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, so long as the received transmission is powerful enough.
In order to use Bluetooth, a device must be compatible with certain Bluetooth profiles. These define the possible applications and uses.
List of applications
- Wireless control of and communication between a cell phone and a hands free headset or car kit. This was one of the earliest applications to become popular.
- Wireless networking between PCs in a confined space and where little bandwidth is required.
- Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.
- Transfer of files between devices via OBEX.
- Transfer of contact details, calendar appointments, and reminders between devices via OBEX.
- Replacement of traditional wired serial communications in test equipment, GPS receivers and medical equipment.
- For controls where infrared was traditionally used.
- Sending small advertisements from Bluetooth enabled advertising hoardings to other, discoverable, Bluetooth devices.
- Wireless control of a games console – Nintendo's Wii and Sony's PlayStation 3 both use Bluetooth technology for their wireless controllers.
Bluetooth vs. Wi-Fi in networking
Bluetooth and Wi-Fi both have their places in today’s offices, homes, and on the move: setting up networks, printing, or transferring presentations and files from PDAs to computers.
Bluetooth is in a variety of new products such as phones, printers, modems, and headsets. Bluetooth is acceptable for situations when two or more devices are in close proximity with each other and don't require high bandwidth. Bluetooth is most commonly used with phones and hand-held computing devices, either using a Bluetooth headset or transferring files from phones/PDAs to computers. Since Bluetooth uses short-range radio frequencies, it is not as effective for setting up networks that can be accessed from remote locations as Wi-Fi is.
Bluetooth also simplified the discovery and setup of services. Wi-Fi is more analogous to the traditional Ethernet network and requires configuration to set up shared resources, transmit files, set up audio links (e.g. headsets and hands-free devices), whereas Bluetooth devices advertise all services they actually provide; this makes the utility of the service that much more accessible, without the need to worry about network addresses, permissions and all the other considerations that go with typical networks.
Wi-Fi uses the same radio frequencies as Bluetooth, but with higher power consumption resulting in a stronger connection. As mentioned earlier, Wi-Fi is sometimes, but rarely, called "wireless Ethernet". Although this description is inaccurate, it provides an indication of Wi-Fi's relative strengths and weaknesses. Wi-Fi requires more setup but is better suited for operating full-scale networks as it enables a faster connection, better range from the base station, and better security than Bluetooth.
One method for comparing the efficiency of wireless transmission protocols such as Bluetooth and Wi-Fi is called spatial capacity.
Specifications and Features
The Bluetooth specification was first developed in 1994 by Sven Mattison and Jaap Haartsen, who were working for Ericsson Mobile Platforms in Lund, Sweden at the time. The specifications were formalized by the Bluetooth Special Interest Group (SIG). The SIG was formally announced on May 20, 1998. Today it has over 6000 companies worldwide. It was established by Ericsson, Sony Ericsson, IBM, Intel, Toshiba and Nokia, and later joined by many other companies as Associate or Adopter members. Bluetooth is also known as IEEE 802.15.1.
Bluetooth 1.0 and 1.0B
Versions 1.0 and 1.0B had many 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 setback for services planned to be used in Bluetooth environments, such as Consumerium.
- Many errors found in the 1.0B specifications were fixed.
- Added support for non-encrypted channels.
- Received Signal Strength Indicator (RSSI)
This version is backwards compatible with 1.1 and the major enhancements include
- Adaptive Frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of 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
This version is backwards compatible with 1.x. The main enhancement is the introduction of Enhanced Data Rate (EDR) of 3.0 Mbps. This has the following effects (Bluetooth SIG, 2004):
- 3 times faster transmission speed—up to 10 times in certain cases (up to 2.1 Mbit/s).
- 100 meter range (Depends on the class of the device)
- Lower power consumption through a reduced duty cycle.
- Simplification of multi-link scenarios due to more available bandwidth.
- Further improved BER (bit error rate) performance.
A draft version of the Bluetooth Core Specification Version 2.1 + EDR is now availiable from the Bluetooth website.
Future of Bluetooth
The next version of Bluetooth technology, currently code-named Lisbon, includes a number of features to increase security, usability and value of Bluetooth. The following features are defined:
- Atomic Encryption Change - allows encrypted links to change their encryption keys periodically, increasing security, and also allowing role switches on an encrypted link
- Extended Inquiry Response - provides more information during the inquiry procedure to allow better filtering of devices before connection. This information includes the name of the device, and a list of services, with other information.
- Sniff Subrating - reducing the power consumption when devices are in the sniff low-power mode, especially on links with asymmetric data flows. Human interface devices (HID) are expected to benefit the most, with mice and keyboards increasing the battery life from 3 to 10 times those currently used.
- QoS Improvements - these will enable audio and video data to be transmitted at a higher quality, especially when best effort traffic is being transmitted in the same piconet.
- Simple Pairing - this improvement will radically improve the pairing experience for Bluetooth devices, while at the same time increasing the use and strength of security. It is expected that this feature will significantly increase the use of Bluetooth.
Bluetooth technology already plays a part in the rising Voice over IP (VOIP) scene, with Bluetooth headsets being used as wireless extensions to the PC audio system. As VOIP becomes more popular, and more suitable for general home or office users than wired phone lines, Bluetooth may be used in Cordless handsets, with a base station connected to the Internet link.
The version of Bluetooth after Lisbon, code-named Seattle, has many of the same features, but is most notable for plans to adopt Ultra-wideband radio technology. This will allow Bluetooth use over UWB radio, enabling very fast data transfers, synchronizations and file pushes, while building on the very low power idle modes of Bluetooth. The combination of a radio using little power when no data is transmitted, and a high data rate radio used to transmit bulk data, could be the start of software radios. Bluetooth, given its worldwide regulatory approval, low power operation, and robust data transmission capabilities, provides an excellent signalling channel to enable the soft radio concept.
On 28 March 2006, the Bluetooth Special Interest Group announced its selection of the WiMedia Alliance Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) version of Ultra-wideband (UWB) for integration with current Bluetooth wireless technology. UWB integration will create a version of the globally popular Bluetooth wireless technology with a high speed/high data rate option. This new version of Bluetooth technology will meet the high-speed demands of synchronizing and transferring large amounts of data as well as enabling high quality video and audio applications for portable devices, multi-media projectors and television sets, wireless VOIP. At the same time, Bluetooth technology will continue catering to the needs of very low power applications such as mice, keyboards and mono headsets, enabling devices to select the most appropriate physical radio for the application requirements, thereby offering the best of both worlds.
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 "group of up to 8 devices" (1 master and 7 slaves) is called a piconet. A piconet is an ad-hoc computer network of devices using Bluetooth technology protocols to allow one master device to interconnect with up to seven active slave devices (because a three-bit MAC address is used). Up to 255 further slave devices can be inactive, or parked, which the master device can bring into active status at any time.
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. These devices have yet to come, though are supposed to appear in 2007.
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
Anything 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 that are required to get additional information about remote devices. This can get confusing as, for example, there could be several phones in range named "T610" (see "Bluejacking").
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. Pairing algorithms are sometimes manufacturer-specific for transmitters and receivers used in applications such as music and entertainment.
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. Bluetooth is often thought of as wireless USB whereas Wi-Fi is wireless Ethernet, both operating at much lower bandwidth than the cable systems they are trying to replace. However, this analogy is not accurate since unlike USB, Bluetooth does not require the presence of a host PC.
Many USB Bluetooth adapters are available, some of which also include an IrDA adapter.
Older (pre-2003) Bluetooth adapters, however, limit the amount of services by offering only the Bluetooth Enumerator and a less-powerful incarnation of Bluetooth Radio. Such devices are able to link computers via Bluetooth, but they unfortunately don't offer much in the way of the twelve or more services that modern adapters are able to utilize.
Bluetooth uses the SAFER+ algorithm for authentication and key generation. The initialisation key and master key are generated using the E22 algorithm . 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.
In April 2004, security consultant firm @Stake (now Symantec) 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 Lab 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 April 2005, Cambridge University security researchers published results of their actual implementation of passive attacks against the PIN-based pairing between commercial Bluetooth devices, confirming the attacks to be practicably fast and Bluetooth's symmetric key establishment method to be vulnerable. To rectify this vulnerability, they carried out an implementation which showed that stronger, asymmetric key establishment is feasible for certain classes of devices, such as handphones.
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.
In April 2006, researchers from Secure Network and F-Secure published a report which warns of the huge number of devices left in a visible state, and issued statistics on the spread of various bluetooth services and the ease of spread of an eventual bluetooth worm.
In October 2006, at the Luxemburgish Hack.lu Security Conference , Kevin Finistere and Thierry Zoller demonstrated and released a remote root shell over Bluetooth on MAC OSX 10.3.9 and 10.4, furthermore they demoed the first public release and display of a Bluetooth PIN and Linkkeys cracker which is based on the research of Wool and Shaked.
- See also: Wireless electronic devices and health, Electromagnetic radiation hazard, Electrical sensitivity, Specific absorption rate, Bioelectromagnetics, and Radiobiology
Bluetooth uses the microwave radio frequency spectrum in the 2.4 GHz to 2.4835 GHz range. Previous electromagnetic hazard studies dating from the 50's through the 80's, including more recent studies (see http://www.cdc.gov/niosh/hhe/reports/pdfs/2003-0111-2909.pdf) concluded that low power signals with frequencies as high as 1.5 GHz - 2 GHz do not cause irreversible damage to human tissue. The radiated output power of Bluetooth devices is low when compared to other widely used mobile devices, so it is assumed that the potential for health risks are also correspondingly lower. Bluetooth devices can operate continuously or sporadically (on demand), so total exposure to EMF radiation is very variable.
Origin of the name and the logo
The name Bluetooth is derived from the cognomen of a 10th century king, Harald Bluetooth King of Denmark and Norway from 935 and 936 respectively, to 940. He is known for his unification of previously warring tribes from Denmark (including Scania, present-day Sweden, where the Bluetooth technology was invented) and Norway. Bluetooth likewise was intended to unify different technologies like computers and mobile phones. The name may have been inspired less by the historical Harald than the loose interpretation of him in The Long Ships by Frans Gunnar Bengtsson, a Swedish best-selling Viking-inspired novel. The Bluetooth logo merges the Nordic runes analogous to the modern Latin H and B: (Haglaz) and (Berkanan). The logo is similar to an older logo for Beauknit Textiles, a division of Beauknit Corporation. That logo, using the obvious connection of a reversed K and B for Beauknit, is wider and has rounded corners, but is otherwise the same.
In 1998, Ericsson, IBM, Intel, Motorola, Nokia and Toshiba formed the consortium among themselves and adopted the code name Bluetooth for their proposed open specification. In December 1999, 3Com, Lucent Technologies, Microsoft and Motorola joined the initial founders as the promoter group. Since that time, Lucent Technologies transferred their membership to their spinoff Agere Systems and 3Com has left the Promoter group. Most recently, Nintendo has installed Bluetooth on its new video game controller, the Wii Remote, to communicate with the Wii console.
- Advanced Audio Distribution Profile
- BlueZ, a Linux Bluetooth stack
- lwBT, a light-weight Bluetooth stack for embedded systems
- Cable spaghetti — a problem wireless technology hopes to solve
- Origin of the word Bluetooth
- Service Location Protocol
- Universal Plug and Play
- Vehicular communication systems
- Wibree A complementary standard with lower power consumption, developed by Nokia
- ZigBee A low power light weight wireless protocol in the 2.4 G band
- PearlBlue A OEM Bluetooth module for embedded microprocessor applications
- Bluetooth SIG (November 8, 2004). Bluetooth Special Interest Group Launches Bluetooth Core Specification Version 2.0 + Enhanced Data Rate. Press release.
- Bluetooth specifications, The Official Bluetooth® Wireless SIG Site
- Bluetooth.org — The Official Bluetooth Membership Site
- How Bluetooth Works at HowStuffWorks
- Official Linux Bluetooth protocol stack