The Security behind Bluetooth
Frequency Hopping Spread Spectrum (FHSS)(used in Bluetooth) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. It is used as a multiple access method in the frequency-hopping code division multiple access (FH-CDMA) scheme.
A spread-spectrum transmission offers three main advantages over a fixed-frequency transmission:
1. Spread-spectrum signals are highly resistant to narrowband interference. The process of re-collecting a spread signal spreads out the interfering signal, causing it to recede into the background.
2. Spread-spectrum signals are difficult to intercept. A spread-spectrum signal may simply appear as an increase in the background noise to a narrowband receiver. An eavesdropper may have difficulty intercepting a transmission in real time if the pseudorandom sequence is not known.
3. Spread-spectrum transmissions can share a frequency band with many types of conventional transmissions with minimal interference. The spread-spectrum signals add minimal noise to the narrow-frequency communications, and vice versa. As a result, bandwidth can be used more efficiently.
FHSS is a wireless technology that spreads its signal over rapidly changing frequencies. Each available frequency band is divided into sub-frequencies. Signals rapidly change ("hop") among these in a pre-determined order. Interference at a specific frequency will only affect the signal during that short interval. A sub-type of FHSS used in Bluetooth wireless data transfer is adaptive frequency hopping spread spectrum (AFH). Adaptive Frequency Hopping allows Bluetooth to adapt to the environment by identifying fixed sources of interference and excluding them from the list of available channels. This process of re-mapping also involves reducing the number of channels to be used by Bluetooth. The Bluetooth Specification requires a minimum set of at least twenty channels.
Frequency hopping was first used for military electronic countermeasures.
(See Hedy Lamarr Links)
https://en.wikipedia.org/wiki/Hedy_Lamarr
https://www.google.com/patents/US2292387
Because this radio communication occurs only for brief periods on a radio channel and the frequency hop channel numbers are only known to authorized receivers of the information, transmitted signals that use frequency hopping are difficult to detect and monitor.
To receive information from the transmitter, the receiver uses the exact same hopping sequence. When the transmitter and receiver frequency hopping sequences occur exactly at the same time, information can transfer from the transmitter to the receiver.
Bluetooth provides three basic security services
Authentication & Authorization: This is the process of determining who is at the other end of a Bluetooth link and if their device should have access to yours.
Encryption & Data Protection: Bluetooth encrypts your data and only allows approved devices to decrypt it, making it much more difficult to for unauthorized users to capture and decipher your personal information.
Privacy & Confidentiality: In addition to encrypting the data being transmitted, the latest version of Bluetooth also makes it possible to encrypt the address of the Bluetooth device itself. This makes it nearly impossible for someone else to track a device, like your phone as it moves from place to place.
Bluetooth adheres to U.S. federal security regulations, ensuring that all Bluetooth devices are capable of meeting and exceeding strict government security standards.
NIST Compliant: The National Institute of Technology develops security standards and guidelines for federal agencies to protect their information and information systems.
FIPS Approved: These Federal Information Processing Standards are developed by NIST in accordance with the Federal Information Security Management ACT (FISMA).
www.bluetooth.org
http://www.fda.gov/MedicalDevices/DigitalHealth/ucm373213.htm
