Bluetooth
Stephen Carter
March 19, 2002
Quote of the Day
"I don't have to be careful, I've got a gun.“
-Homer Simpson
1
About Bluetooth
• Developed by a group called Bluetooth Special
Interest Group (SIG), formed in May 1998
• Founding members were Ericsson, Nokia, Intel,
IBM and Toshiba
• Almost all of the biggest companies in the
telecommunications business have joined the
Bluetooth SIG and the number of the participating
companies is now over 1,500
What is Bluetooth?
• A cable-replacement technology that can be used
to connect almost any device to any other device
• Radio interface enabling electronic devices to
communicate wirelessly via short range (10
meters) ad-hoc radio connections
• A standard for a small, low cost (~ $5), low
power, radio based chip to be plugged into
computers, printers, keyboards, monitors, mobile
phones, refrigerators??, PDAs, etc…
2
Bluetooth details
• Uses the radio range of 2.45 GHz
• Theoretical maximum bandwidth is 1 Mb/s
• Several Bluetooth devices can form an ad
hoc network called a “piconet”
– In a piconet one device acts as a master (sets
frequency hopping behavior) and the others as
slaves
– Example: A conference room with many
laptops wishing to communicate with each
other
Bluetooth v. 802.11 ?
• Bluetooth
– Designed for quick, seamless short range networks
– Features low power consumption, small protocol stack,
robust data & voice transfer
– Cheap price
– Good choice for WPAN (Wireless Personal Area Networks)
• 802.11
– Designed for infrequent mobility, IP-based data transmission
– Medium range and high data rate
– At least 10x the price of bluetooth
– Good choice for WLAN (Wireless Local Area Networks)
3
Bluetooth v. 802.11 ?
WPAN technologies enable
users to establish ad hoc, wireless
communications for devices
(such as PDAs, cellular phones,
or laptops) that are used within a
personal operating space (POS).
A POS is the space surrounding
a person, up to a distance of
10 meters.
No serious competition exists between the Bluetooth & 802.11.
They are aimed at different markets and different roles.
Bluetooth v. 802.11 ?
• IEEE has established the 802.15 working
group for WPANs. This working group is
developing a WPAN standard, based on the
Bluetooth version 1.0 specification. Key
goals for this draft standard are low
complexity, low power consumption,
interoperability, and coexistence with
802.11 networks.
4
Bluetooth Specification Protocol Stack
Bluetooth Specification Protocol Stack
• Radio
– defines the requirements for a Bluetooth transceiver operating in the 2.4 GHz ISM
band.
• Baseband
– describes the specification of the Bluetooth Link Controller (LC) which carries out the
baseband protocols and other low-level link routines.
• LMP
– used by the Link Managers (on either side) for link set-up and control.
• HCI
– provides a command interface to the Baseband Link Controller and Link Manager, and
access to hardware status and control registers.
• L2CAP
– supports higher level protocol multiplexing, packet segmentation and reassembly, and
the conveying of quality of service information.
• RFC
– provides emulation of serial ports over the L2CAP protocol. The protocol is based on
the ETSI standard TS 07.10
• SDP
– The Service Discovery Protocol (SDP) provides a means for applications to discover
which services are provided by or available through a Bluetooth device. It also allows
applications to determine the characteristics of those available services
5
Bluetooth Security
• Must consider standard ad hoc network issues
– Availability
• DOS attacks easy to perform
• Routing protocol attacks
• Battery Exhaustion attacks
– Authorization & Key Management
– Confidentiality & Integrity
• Anyone can sniff messages from the air
• Radio Interference
Bluetooth Security (cont)
• Every bluetooth device has 4 entities for maintaining
security
– Bluetooth device address
• 48-bit address that is unique for each Bluetooth device and defined
by IEEE
– Private authentication key
• 128-bit random number used for authentication purposes
– Private encryption key
• 8-128 bits in length that is used for encryption
– Random number
• frequently changing 128-bit random or pseudo-random number that
is made by the Bluetooth device itself
6
Bluetooth Security (cont)
• In Bluetooth Generic Access Profile, security is
divided into 3 modes
– non-secure
– service level enforced security
– link level enforced security
• device initiates security procedures before the channel is
established
• Device security modes
– Trusted or untrusted
• Service security modes
– Authorization and Authentication
– Authentication only
– Open to all
Bluetooth Security (cont)
• Security mechanisms more complex than
802.11 due to the “ad-hocness”
• A number of weaknesses and vulnerabilities
exist in Bluetooth security
• May be adequate for non-sensitive data and
smaller applications, but money transactions
or military applications???
• Sound familiar???
7
Credits
• Palowireless Bluetooth Resource Center
• Microsoft XP Help and Support Center
• J. Vainio, “BlueTooth Security,” TR 2000-
05-25
