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Bluetooth
Courtesy: Wikipedia
BLUETOOTH - SHORT-RANGE
COMMUNICATIONS STANDARD
Bluetooth is a cable
replacement technology.
Bluetooth is a
proposed Radio Frequency (RF) specification for
short-range, point-to-multipoint voice and data
transfer.�
Bluetooth is an industrial
specification for wireless personal area
networks (PANs) first developed by Ericsson,
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.
Introduction
The system is named after a Danish
king Harald Bl�tand (Harold Bluetooth in
English), King of Denmark and Norway from 935
and 936 respectively, to 940 known for his
unification of previously warring tribes from
Denmark, Norway and Sweden. Bluetooth likewise
was intended to unify different technologies
like computers and mobile phones. The Bluetooth
logo merges the Nordic runes for H and B. This
is the official story: however, the actual
Harald Bl�tand that was referred to in naming
Bluetooth was most probably the liberal
interpretation given to him in The Long Ships by
Frans Gunnar Bengtsson, a Swedish best-selling
Viking-inspired novel.
Bluetooth provides a way to connect and exchange
information between devices like personal
digital assistants (PDAs), mobile phones,
laptops, PCs, printers and digital cameras via a
secure, low-cost, globally available short range
radio frequency.
Bluetooth lets these devices talk to each other
when they come in range, even if they're not in
the same room, as long as they are within 10
metres (32 feet) of each other.
General
information
A typical Bluetooth mobile phone
headset
The latest version
currently available to consumers is 2.0, but few
manufacturers have started shipping any products
yet. Apple Computer, Inc. offered the first
products supporting version 2.0 to end customers
in January 2005. The core chips have been
available to OEMs (from November 2004), so there
will be an influx of 2.0 devices in mid-2005.
The previous version, on which all earlier
commercial devices are based, is called 1.2.
Bluetooth is a wireless radio standard primarily designed for low power
consumption, with a short range (up to 10 meters [1]
(https://www.bluetooth.org/admin/bluetooth2/faq/view_record.php?id=49),
) and with a low-cost transceiver microchip in each device.
It can be used to wirelessly connect peripherals
like printers or keyboards to computers, or to
have PDAs communicate with other nearby PDAs or
computers.
Cell phones with integrated Bluetooth technology
have also been sold in large numbers, and are
able to connect to computers, PDAs and,
specifically, to handsfree devices. BMW was the
first motor vehicle manufacturer to install
handsfree Bluetooth technology in its cars,
adding it as an option on its 3 Series, 5 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.
The standard also includes support for more
powerful, longer-range devices suitable for
constructing wireless LANs.
A Bluetooth device playing the role of "master"
can communicate with up to 7 devices playing the
role of "slave". At any given instant in time,
data can be transferred between the master and
one 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). These groups of up to 8 devices (1
master and 7 slaves) are called piconets.
The Bluetooth specification also allows
connecting two 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 within the next two
years.
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.
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 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 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.
Many USB Bluetooth adapters are available, some
of which also include an IrDA adapter.
Embedded
Bluetooth
Bluetooth devices and modules are
increasingly being made available which come
with an embedded stack and a standard UART port.
The UART protocol can be as simple as the
industry standard AT protocol, which allows the
device to be configured to cable replacement
mode. This means it now only takes a matter of
hours (instead of weeks) to enable legacy
wireless products that communicate via UART
port.
Features by
version
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.
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 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.
Received Signal Strength Indicator (RSSI)
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
and the major enhancements include
Non-hopping narrowband channel(s) introduced.
These are faster but have been criticised as
defeating a built-in security mechanism of
earlier versions; however frequency hopping is
hardly a reliable security mechanism by today's
standards. Rather, Bluetooth security is based
mostly on cryptography.
Broadcast/multicast support. Non-hopping
channels are used for advertising Bluetooth
service profiles offered by various devices to
high volumes of Bluetooth devices
simultaneously, since there is no need to
perform handshaking with every device. (In
previous versions the handshaking process takes
a bit over one second.)
Enhanced Data Rate (EDR) of 2.1 Mbit/s.
Built-in quality of service.
Distributed media-access control protocols.
Faster response times.
Halved power consumption due to shorter duty
cycles.
Future
Bluetooth uses
One of the ways Bluetooth technology
may become useful is in Voice over IP. When VOIP
becomes more widespread, companies may find it
unnecessary to employ telephones physically
similar to today's analogue telephone hardware.
Bluetooth may then end up being used for
communication between a cordless phone and a
computer listening for VOIP and with an infrared
PCI card acting as a base for the cordless
phone. The cordless phone would then just
require a cradle for charging. Bluetooth would
naturally be used here to allow the cordless
phone to remain operational for a reasonably
long period.
Security
concerns
In November 2003, Ben and Adam Laurie
from A.L. Digital Ltd. (http://www.thebunker.net/index.html)
discovered that serious flaws in Bluetooth
security 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 (http://trifinite.org/trifinite_group.html)
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 (http://trifinite.org/trifinite_stuff_bluebug.html)
was used for this experiment.
In April 2004, security consultants @Stake
(http://www.atstake.com) 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 (http://www.theregister.co.uk/2004/06/15/symbian_virus/)
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. The virus was written
as a proof-of-concept by a group of virus
writers known as 29a and sent to anti-virus
groups. Because of this, it should not be
regarded as a security failure of either
Bluetooth or the Symbian OS. It has not
propagated 'in the wild'.
In August 2004, a world-record-setting
experiment (http://trifinite.org/trifinite_stuff_lds.html)
(see also Bluetooth sniping) showed that with
directional antennas the range of class 2
Bluetooth radios could be extended to one mile.
This enables attackers to access vulnerable
Bluetooth-devices from a distance beyond
expectation.
Bluetooth uses the SAFER+ algorithm for
authentication and key generation.
Bluetooth
profiles
In order to use Bluetooth, a device
must be able to interpret certain Bluetooth
profiles. These define the possible
applications. Following profiles are defined:
Generic Access Profile (GAP)
Service Discovery Application Profile (SDAP)
Cordless Telephony Profile (CTP)
Intercom Profile (IP)
Serial Port Profile (SPP)
Headset Profile (HSP)
Dial-up Networking Profile (DUNP)
Fax Profile
LAN Access Profile (LAP)
Generic Object Exchange Profile (GOEP)
Object Push Profile (OPP)
File Transfer Profile (FTP)
Synchronisation Profile (SP)
This profile allows synchronisation of Personal
Information Manager (PIM) items. As this profile
originated as part of the infrared
specifications but has been adopted by the
Bluetooth SIG to form part of the main Bluetooth
specification, it is also commonly referred to
as IrMC Synchronization.
Hands-Free Profile (HFP)
Human Interface Device Profile (HID)
Hard Copy Replacement Profile (HCRP)
Basic Imaging Profile (BIP)
Personal Area Networking Profile (PAN)
Basic Printing Profile (BPP)
Advanced Audio Distribution Profile (A2DP)
Audio Video Remote Control Profile (AVRCP)
SIM Access Profile (SAP)
Compatibility of products with profiles can be
verified on the Bluetooth Qualification website
(http://qualweb.bluetooth.org/Template2.cfm?LinkQualified=QualifiedProducts).
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