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* Re: [Bluez-devel] bd_addr question
@ 2004-03-10  7:45 Michael Schmidt
  2004-03-10 11:22 ` Steven Singer
  0 siblings, 1 reply; 7+ messages in thread
From: Michael Schmidt @ 2004-03-10  7:45 UTC (permalink / raw)
  To: jessieh; +Cc: bluez-devel

Hi Jessica,

> Sorry, I worded it poorly.  I'm a graduate student researching
> privacy issues related to Bluetooth, which I'm pretty new to.  I'm
> trying to work a way around the fact that each device address is
> unique therefore trackable.  I was wondering if I were to buy a
> Bluetooth transmitter and build my own device, can I change the
> bd_addr that is stored by the chip's manufacturer?  Which
> layer/module is in charge of reading that unique bd_addr?  I hope
> that makes more sense!

Check the source files of the AXIS OpenBT stack
(http://sourceforge.net/projects/openbt/) for vendor-specific commands 
on how to change the BD_ADDR of certain Ericsson and CSR modules (sorry, 
I forgot the precise files where these commands are located in). After 
performing the address change, you need to hard-reset (i.e. typically 
disconnect) the modules to make the change effective.

Keep in mind that you break some of the BT functionality when you use 
variable BD_ADDRs: The pairing-based security mechanisms (authentication 
and encryption) rely on a constant BD_ADDR. I guess there is more 
functionality that is affected by the change.


Hope this helps,

Michael


-- 
=================================================
Michael Schmidt
-------------------------------------------------
Institute for Data Communications Systems
University of Siegen, Germany
-------------------------------------------------
http:   www.nue.et-inf.uni-siegen.de/~schmidt/
e-mail: schmidt@nue.et-inf.uni-siegen.de
mobile: +49 179 7810214
=================================================


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^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [Bluez-devel] bd_addr question
@ 2004-03-10 16:04 Mark RISON
  0 siblings, 0 replies; 7+ messages in thread
From: Mark RISON @ 2004-03-10 16:04 UTC (permalink / raw)
  To: bluez-devel

Steven Singer <steven.singer@csr.com>:

>Michael Schmidt wrote:
> > Keep in mind that you break some of the BT functionality when you use
> > variable BD_ADDRs: The pairing-based security mechanisms (authentication
> > and encryption) rely on a constant BD_ADDR. I guess there is more
> > functionality that is affected by the change.
>Don't forget that Bluetooth addresses must be unique otherwise unpleasant
>things happen.
>Bluetooth addresses come out of the same address space as MAC addresses,
>if you want to use your own then you need to get an OUI or IAB allocation
>from the IEEE.

Well, you could use a MAC address with the U(niversal)/L(ocal) bit set,
which would correspond to a BD_ADDR with bit 9 of the NAP set, as long
as you can guarantee its uniqueness (which in practice means you have
control of all the devices which might participate in your network; bear in
mind that some MAC addresses were allocated with that bit set in pre-IEEE
days).  You don't have to buy/register locally-administered MAC addresses.

>The BD ADDR <-> MAC point is important. If you start running BNEP
>(Bluetooth Network Encapsulation Protocol = Ethernet over Bluetooth)
>then the Bluetooth device will use its Bluetooth address as its Ethernet
>MAC address. This means that you can't simply take the MAC address from
>another device on your system (say an Ethernet card) and use it as your
>Bluetooth address.

Unless you refrain from using that Ethernet card in the same network as
your Bluetooth device.  (This is/was the basis of a popular way to buy a few
MAC addresses: buy a few bargain-basement NICs, read their BD_ADDRs,
and junk the NICs).

Another top tip: don't pick addresses with the I(ndividual)/G(roup) bit set
(i.e. multicast addresses), which would correspond to a BD_ADDR with
bit 8 of the NAP set.  BNEP devices are almost certain to get very confused
by this!

Mark

--
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-- http://www.nenie.org/cpcip/
"Z88 vs CPC? Christ. How did we miss that platform war?"
-- http://www.ntk.net/index.cgi?back=archive00/now0128.txt&line=110#l

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^ permalink raw reply	[flat|nested] 7+ messages in thread
* [Bluez-devel] bd_addr question
@ 2004-03-09 20:12 Jessica Huang
  2004-03-09 21:24 ` Marcel Holtmann
                   ` (2 more replies)
  0 siblings, 3 replies; 7+ messages in thread
From: Jessica Huang @ 2004-03-09 20:12 UTC (permalink / raw)
  To: bluez-devel

Hi,
I'm not sure if this is the right place to ask, but I had a question about 
the Bluetooth Device Address.  From my understanding, the BD_ADDR is stored 
on the Bluetooth transmitter.  I was wondering if it is possible to 
intercept that address and provide some arbitrary one.  Could someone 
please explain how this address is accessed and by what modules?
Thanks,
Jessica  



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_______________________________________________
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^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2004-03-10 16:04 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2004-03-10  7:45 [Bluez-devel] bd_addr question Michael Schmidt
2004-03-10 11:22 ` Steven Singer
  -- strict thread matches above, loose matches on Subject: below --
2004-03-10 16:04 Mark RISON
2004-03-09 20:12 Jessica Huang
2004-03-09 21:24 ` Marcel Holtmann
     [not found] ` <5.2.1.1.2.20040309190444.02e6e250@po14.mit.edu>
2004-03-10  0:23   ` Marcel Holtmann
2004-03-10  9:46 ` Collin R. Mulliner

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