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Hi.
Anyone who knows how exactly bluetooth works? Just wondering, what happens if two people have the same Bluetooth handsfreeset and are using the devices, standing not far from eachother? Is it possible that person A's bluetooth pics up person B's bluetooth phone? Like if A enables his phone for Bluetooth and B got a bluetooth handsfree (Bluespoon). Will the phone connect to the "wrong" device?
Just curious... Maybe Jan could answer this question?
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Posted: 2002-01-22 22:00:00
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On 2002-01-22 22:00, johanch wrote:
Hi.
Anyone who knows how exactly bluetooth works? Just wondering, what happens if two people have the same Bluetooth handsfreeset and are using the devices, standing not far from eachother? Is it possible that person A's bluetooth pics up person B's bluetooth phone? Like if A enables his phone for Bluetooth and B got a bluetooth handsfree (Bluespoon). Will the phone connect to the "wrong" device?
Just curious... Maybe Jan could answer this question?
Johan : I dont know all the tech-stuff about bluetooth.
When you pair a headset with a phone, you have to write in a headset-code, in the phone.
The pairing and the code links the two devices together.
We actually sat at the last meeting at Nextlink with 3 different bluetooth headsets, and 3 different phones,..all of them were turned on, and using bluetooth at the same time, hehe. No interference at all.
All bluetooth headsets have to be paired with their phones. So they can be used with that specific phone. They wont work with another phone, unless you pair them.
If a bluetooth device (phone/pda) have to be able to "see" or "look for" another bluetooth device,..it needs to be in "search-mode". It will then search the area for up to e.g. 3 minutes for other bluetooth-devices. The other bluetooth device need to be in "ON-mode".
This should pretty much answer your question, right
Jan
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Posted: 2002-01-22 23:06:00
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I guess it's very much the same as having three mobiles in the same room - they're all using radio waves of a similar frequency to communicate, but you never get interference do you?
As to why... I have no idea
Adam
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Posted: 2002-01-23 11:15:00
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This is avoided by using the security:
The procedures for security use four values: the device address(which is public), a private authentication key(128 bits), private encryption key(8-128 bits, configurable) and a random number. As the keys have to be secret, they cannot be obtained by inquiry. The exchange procedures will be described below. The security procedure requires a secret PIN to be known to the user(or stored by his application) for accessing a particular device. The main steps in the procedure are:
1. An initialization key is generated using the PIN, the length of the PIN, a random number and the device address. he dependence on the device address makes it more difficult for a fraudulent device to try a large number of PINs as each has now to be tried with different device addresses.
2. An authentication procedure is carried out using the challenge response scheme. The verifier unit sends a random number generated by a specific process for the authentication. This random number is such that a claimant device which has the correct initialization key (or a link key if the devices had exchanged that during an earlier communication) and the required device address, will be able to produce a response number which is known to the verifier. This response number is sent back and checked by the verifier.
3. The claimant may also carry out a verification on the verifier using a similar procedure as above.
4. Each Bluetooth unit has a unit key, installed in its non volatile memory. The device now uses the initialization key to encrypt this unit key and sends it to the other device which decrypts it using the initialization key exchanged earlier.
5. The second device may add its own unit key to the unit key of the first device and generate a combination link key if both the devices are capable of handling this. Otherwise the unit key of one of the devices is treated as the link key. The link key is communicated to the first device. The initialization key is discarded.
6. An encryption key is now generated from the link key, a random number and another number obtained from a fixed procedure. Both the devices can generate this encryption key as all the required information is known to both devices. This key with some modification as described later, is used to encrypt data payloads.
The link key is remembered. If another link is to be established between the two devices at a later time, this link key can be directly used. This eliminates the need to send keys over the channel again. Thus, data can be transmitted securely with minimum user interaction.
a bit technical but it works.
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Posted: 2002-01-23 11:55:00
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Sorry, forgot to add something:
How is the situation handed if two devices launch an inquiry simultaneously?
Answer:
When two devices start an inquiry simultaneously, then they cannot discover ech other in that inquiry sequence. (They do not cause collissions for other devices as the inquiry hop sequence is different for the two devices.) To prevent the devices never being able to discover each other, the specification requires that the interval between two inquiries be random. This ensures that the two devices which collided once will not collide again in the next inquiry.
So there is no collission if you do not want it but in a so called "pictonet" you will be able to have one device to talk/listen to two or more devices. 5if you want it and pair the devices)
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Posted: 2002-01-23 12:16:00
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I just got my EPOX BT adapter here in canada, and it is working perfuctlly. I really like it, it's amazing...!
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Posted: 2002-11-03 17:02:00
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is very complicated shit - but as Bill & Ted would say - most excellent
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Posted: 2002-11-03 23:57:00
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