Bluetooth
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All about Bluetooth technology and its infrastructure. Visit my blog http://healthymind786.blogspot.com/
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Bluetooth
- 3. Introduction
- 24. Bluetooth vs Other Wireless Technologies
Notas del editor
- First we move towards the introduction
- RS232 data cables
- FHSS Chops up the data being sent and transmits chunks of it on up to 79 frequencies. 1600 hops/sec- time slot is defined as 625 microseconds Packet 1-5 time slots long FHSS is used to minimize the risk of such interference with systems operating on this Band such as microwave ovens, baby monitors and 802.11 wireless networks. GFSK When we jump from (1,-1 or -1,1), mod waveform changes rapidly, introducing large out of bound spectrum.(no overshoot to a step function input ) Uses Gaussian filter (uses G.Function) to limit its spectral width. GFSK = Baseband pulses(-1,1) gaussian filter FSK modulator FSK = Baseband pulses(-1,1) FSK modulator 1Mb/s with overhead, this effectively becomes 721 kbps. SIG 5 companies joined to form the Bluetooth Special Interest Group (SIG) in 1998. First specification released in July 1999
- Most powerful devices Infrared IrDA (WPAN) : synchronization, link between a phone and a laptop… – Less flexible than Bluetooth, need of a line of site – Comparable data rate Wi-Fi (WLAN) : Wireless LAN access – Far higher bandwidth and data rate than Bluetooth – Higher power consumption than Bluetooth – Requires infrastructure investment
- The slaves in a piconet can only have links to the master. Slaves cannot directly transmit data to one another
- Devices that participate in two or more piconets may act as gateways, forwarding traffic from one piconet to another Bluetooth units can only transmit and receive data in one piconet at a time. As devices in mulltiple piconets divide their time between the piconets, spending some time slots in one and some time slots in another on TDM basis. Devices give notification of inactivation to master that it will be inactive for a predetermined length of time. The device will then have to re-synchronize its clock with its other master. When a slave becomes inactive in a piconet, communications between masters and the other active slaves go on as normal. On the other hand, when a master becomes inactive in its piconet, the slaves will have to wait for it to be active again before communication can resume.
- Protection can be provided by using large pass key which makes computation to find link key more difficult. Best way(100% secure) is to make transfers in an environment that is eavesdropper free Authentication Encryption FHSS
- 1. SNARF ATTACK In Some Bluetooth devices , it is possible to connect to the device without making owner aware of the request and can be used in illegal mobile cloning. entire phonebook, calendar, realtime clock, business card, properties, change log are accessible but other services, such as modems or Internet, WAP and GPRS gateways may be accessed without the owner's knowledge or consent 2. BACKDOOR After creating a trusted relationship, the attacker removes his device name from paired devices register. If owner is monitoring exactly at the time connection is established, they're unable to notice anything unusual entire device can be "backed up" to an attacker's own system 3. BLUEJACKING Blue jacking supports transfer of anonymous messages in public places. Name field = 248 bits. The pairing protocol displays name of the requestor. This name can be used to convey a message to other mobiles. The problem lies in the fact that the protocol being abused is designed for information exchange. The ability to interface with other devices and exchange, update and synchronise data, is the raison d'e^tre of bluetooth. The bluejacking technique is using the first part of a process that allows that exchange to take place, and is therefore open to further abuse if the handshake completes and the "bluejacker" successfully pairs with the target device
- The Bluetooth protocols contain the standard procedures for connections and data exchange between Bluetooth devices.
- The radio layer describes the physical characteristics a Bluetooth device’s receiver-transmitter component must have. These include modulation characteristics, radio frequency tolerance, and sensitivity level.
- See ACL links
- See ACL links OBEX The Object Exchange Protocol (OBEX) is a specification for object data exchange over infrared (IR) links. Examples for using OBEX include exchanging business cards and synchronizing calendar applications.
- Following the profiles procedure supports compatibility Developers can be sure that the applications they create will work with any device that conforms to the Bluetooth specification Profiles are organized into a hierarchy of groups With each group depending upon the features provided by its predecessor.
- GAP GAP defines a consistent means to establish a baseband link between Bluetooth devices. GAP additionally defines: Which features must be implemented in all Bluetooth devices Generic procedures for discovering and linking to devices Basic user-interface terminology Human Interface Device (HID) Profile Describes how to communicate with a HID class device using a Bluetooth link. Serial Port Profile Serial port profile D efines RS-232 serial-cable emulation for Bluetooth devices and uses RFCOMM protocol for that. Dial-up Networking Profile The dial-up networking (DUN) profile is built on the serial port profile and describes how a data-terminal device can use a gateway device(mobile phone/modem) to access a telephone-based network Headset Profile Describes how a Bluetooth-enabled headset should communicate with a computer or other Bluetooth device Hardcopy cable replacement profile The hardcopy cable replacement profile (HCRP)describes how to send rendered data over a Bluetooth link to a device, such as a printer. GOBEX Profile • The generic object exchange profile provides a generic blueprint for other profiles using the OBEX protocol and defines the client and server roles for devices. Object Push Profile • The object push profile defines the roles of push server and push client. These roles are analogous to and must interoperate with the server and client device roles the generic object exchange profile defines. The object push profile focuses on a narrow range of object formats for maximum interoperability. The most common of the acceptable formats is the vCard format. File Transfer Protocol It provides guidelines for applications that need to exchange objects such as files and folders, Synchronization Profile It describes how applications can perform data synchronization, such as between a personal data assistant (PDA) and a computer.
- Infrared IrDA (WPAN) : synchronization, link between a phone and a laptop… – Less flexible than Bluetooth, need of a line of site – Comparable data rate Wi-Fi (WLAN) : Wireless LAN access – Far higher bandwidth and data rate than Bluetooth – Higher power consumption than Bluetooth – Requires infrastructure investment
- Standardized protocol supports interoperability of devices of different types.
- Interference with other devices that use the same frequency such as baby monitors, microwave over etc. FHSS is used to avoid it.
- Many companies are designing and researching impressive bluetooth applications in demand so this shows it has a bright future and it would be difficult for other technology to overcome.
- ACL links and SCO links Inquires who’s there Paging creates a link in piconet Expanding a piconet by excessive pages