Bluetooth Technology Communication and Security


Bluetooth is a specification for the use of low power radio communications to wireless phones, computers, and other network wireless devices over short distances. The Bluetooth definition is a wireless technology that is a worldwide specification for a small form factor, low cost solution that provides a link between mobile devices and other electronic devices.  The name Bluetooth is actually borrowed from Harald Bluetooth, a Denmark king more than 1,000 years ago. The technology of Bluetooth is nothing new, but in many respects it can still seem like more of a buzz word rather than an accepted technology. You may see the ads for Bluetooth enabled devices, although you still may be wondering what it is.


Bluetooth is a low-power WIFI technology that is defined by the Institute of Electrical and Electronics Engineers (IEEE) in their 802.15 standard. It’s designed to connect devices over distances of less than 100 meters. The size of the Bluetooth radio is amazing, as a Bluetooth radio can be built into one or two very small microchips and integrated into any electronic device where wireless operations would be an advantage.

The networks of Bluetooth feature a dynamic topology called PAN (Personal Area Network) or a piconet. The piconets contain a minimum of two and a maximum of eight peer devices. The devices will communicate using protocols that are part of the specification.

Similar to 802.11 b/g wireless and many cordless telephone systems, Bluetooth operates on 2.4 o 2.485 GHz using a spread spectrum, frequency hopping signal (FHSS) – a license free, globally available ISM radio band. The 2.4 GHz band is bit crowded (i.e. Garage door openers, baby monitors, other wireless devices and next generation of mobile phones) with interferces between the devices a bit hard to avoid.  To overcome this challenge, Bluetooth employs a fast frequency hopping scheme and therefore uses shorter packets than other standards within the ISM band. This scheme helps to make Bluetooth communication more robust and more secure.

Frequency hopping scheme

Frequency hopping is a modulation technique which intermittently changes radio channels in a synchronized pattern.  It’s a secret shared by transmitter and receiver.  Switching channels prevents unintended users from eavesdropping on the transmissions between paired devices.  BT also uses Adaptive Frequency Hopping (AFH), an enhancement to FHSS which applies an additional frequency hopping sequence pattern.  When used, overly congested channels are avoided in the channel switching pattern; basically jumping from frequency to frequency within the ISM radio band. After a Bluetooth device sends or receives a packet, it and the device (or devices) it’s communicating with hop to another frequency before the next packet is sent.

This scheme offers three advantages:

1. Allows Bluetooth devices to use the entirety of the available ISM band, while never transmitting from a fixed frequency for more than a short period of time. This helps insure that Bluetooth conforms to the ISM restrictions on the transmission quantity per frequency.

2. Ensures that any interference won’t last long. Any packet that doesn’t arrive safely to its destination can be resent to the next frequency.

3. Provides a base level of security as it’s very hard for an eavesdropping device to predict which next frequency the Bluetooth devices will use.

The technical specifications of Bluetooth will indicate a maximum transfer rate of around 1 MBps, all depending on the class of that particular device. The speed is a fraction of what is offered by wireless standards, so it’s obvious that Bluetooth doesn’t really pose a threat to replacing your wireless network.

In the key marketplace of wireless and handheld devices, the closest competitor to Bluetooth is infrared. Infrared holds many key features, although the line of sight it provides doesn’t go through walls or through obstacles like that of the Bluetooth technology.

Unlike infrared, Bluetooth isn’t a line of sight.  Bluetooth has several positive features and one would be extremely hard pressed to find downsides when given the current competition. The only real downside is the data rate; Infrared, can have data rates of up to 4 MBps for data transfer.

Overall wireless technology downsides/disadvantages is it has a weak encryption cipher, E0 (128-bit key). Attack methods have been developed that have proven the cipher to be no stronger than a 38-bit key, and unfortunately adding more bits to the key does not improve security whatsoever.  Also, buffer overflow attacks; bluejacking attacks, where unsolicited messages are sent to a phone over Bluetooth; and BlueBug attacks, where a malicious user can make calls, eavesdrop on call, send or read Short Message Service (SMS) text messages, download or modify phone data, and reconfigure a victim’s phone.

Bluetooth still remains the best for short range wireless technology. The standard for Bluetooth keeps getting better and better, making it a wireless technology that will be around for years and years to come.

What do you think?

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