[Bluez-users] Key exchange before pairing

[Bluez-users] Key exchange before pairing

[Jordi Jaen Pallares]

[-- Attachment #1: Type: text/plain, Size: 1510 bytes --]

Hi @ll !


I would like to know if it is possible to perform a "peer key exchange" 
prior to the pairing operation, in order to for example, have the peers 
exchange some extra information about them and be able for example to 
look-up different PINs for every different service / connection / device.

I have written a little program using rfcomm sockets (although I am planing 
to change them to BNEP ones) which carries out the data exchange without 
problems as long as the security manager is set to 'none'.

But I would like to be able to replace the normal pairing procedure with 
this "key exchange between bluetooth peers" procedure: 

* it is then possible to trigger (maybe via 'pin_helper' ?) a data exchange 
between the two bluetooth sockets (using raw L2CAP sockets, for example) 
while the devices are _not paired_ and while the security level is set at 
least to authentication ?

* I tried to change the rfcomm "working" sockets program to L2CAP sockets, 
but then I don´t know which Protocol Service MUX (psm) value I might have to 
set for this sockets to have them connect successfully (the one from an 
already existing service, one of the reserved values?!). 

I tried different odd values greater than 1 for the psm (using htobs(psm)) 
and I get the following error message: 

Cannot connect to socket: Connection refused (111)

I would really appreciate it if you could help me out or give me some advise 
on these topics.


Best Regards,


Jordi

[-- Attachment #2: Type: text/html, Size: 1632 bytes --]

Re: [Bluez-users] Key exchange before pairing

[Marcel Holtmann]

Hi Jordi,

> I would like to know if it is possible to perform a "peer key
> exchange" prior to the pairing operation, in order to for example,
> have the peers exchange some extra information about them and be able
> for example to look-up different PINs for every different service /
> connection / device.
>=20
> I have written a little program using rfcomm sockets (although I am
> planing to change them to BNEP ones) which carries out the data
> exchange without problems as long as the security manager is set to
> 'none'.
>=20
> But I would like to be able to replace the normal pairing procedure
> with this "key exchange between bluetooth peers" procedure:=20
>=20
> * it is then possible to trigger (maybe via 'pin_helper' ?) a data
> exchange between the two bluetooth sockets (using raw L2CAP sockets,
> for example) while the devices are _not paired_ and while the security
> level is set at least to authentication ?
>=20
> * I tried to change the rfcomm "working" sockets program to L2CAP
> sockets, but then I don=B4t know which  Protocol Service MUX (psm) valu=
e
> I might have to set for this sockets to have them connect successfully
> (the one from an already existing service, one of the reserved
> values?!).=20
>=20
> I tried different odd values greater than 1 for the psm (using
> htobs(psm)) and I get the following error message:=20
>=20
> Cannot connect to socket: Connection refused (111)
>=20
> I would really appreciate it if you could help me out or give me some
> advise on these topics.

actually I have no idea what you are trying to achieve. Try to include
examples, because I can't follow you.

Regards

Marcel




-------------------------------------------------------
SF.Net email is sponsored by: Discover Easy Linux Migration Strategies
from IBM. Find simple to follow Roadmaps, straightforward articles,
informative Webcasts and more! Get everything you need to get up to
speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click
_______________________________________________
Bluez-users mailing list
Bluez-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-users

Re: [Bluez-users] Key exchange before pairing

[Jordi Jaen Pallares]

[-- Attachment #1: Type: text/plain, Size: 258 bytes --]

Hi Marcel,


I´d like to generate the PIN based on the shared key derived from a Diffie 
Hellman exchange between the bluetooth peers.

Is it possible to trigger this exchange at pairing time using my own 
'pin_helper' program ?

Regards,

Jordi

[-- Attachment #2: Type: text/html, Size: 304 bytes --]

Re: [Bluez-users] Key exchange before pairing

[Marcel Holtmann]

Hi Jordi,

> I=B4d like to generate the PIN based on the shared key derived from a
> Diffie Hellman exchange between the bluetooth peers.

if you wanna use Diffie Hellman, for what reason do you want to use the
pairing and encryption of Bluetooth then.

> Is it possible to trigger this exchange at pairing time using my own
> 'pin_helper' program ?

To exchange data you need a connection first. This means you can only do
this in security mode 1 and 2. The PIN helper can't be used for any of
these task except entering a PIN.

Regards

Marcel




-------------------------------------------------------
SF.Net email is sponsored by: Discover Easy Linux Migration Strategies
from IBM. Find simple to follow Roadmaps, straightforward articles,
informative Webcasts and more! Get everything you need to get up to
speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click
_______________________________________________
Bluez-users mailing list
Bluez-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bluez-users

Re: [Bluez-users] Key exchange before pairing

[Jordi Jaen Pallares]

[-- Attachment #1: Type: text/plain, Size: 1803 bytes --]

Hi Marcel,

first of all, thank you for your comments :-)

2005/6/30, Marcel Holtmann <marcel@holtmann.org>:
> 
> Hi Jordi,
> 
> > I´d like to generate the PIN based on the shared key derived from a
> > Diffie Hellman exchange between the bluetooth peers.
> 
> if you wanna use Diffie Hellman, for what reason do you want to use the 
> pairing and encryption of Bluetooth then.


I would like to use the pairing and encryption of bluetooth as usual, and 
use only the Diffie-Hellman exchange to generate a "stronger" PIN for the 
pairing. 

> Is it possible to trigger this exchange at pairing time using my own 
> > 'pin_helper' program ?
> 
> To exchange data you need a connection first. This means you can only do
> this in security mode 1 and 2. The PIN helper can't be used for any of
> these task except entering a PIN.


But then, is there any other way for the peers to exchange previous 
communication attributes than using the SDP protocol ?

Is it possible to exchange information by previously registering a new 
service (with a fixed PSM) and then negociate the parameters directly using 
L2CAP sockets ?

Regards,

Jordi


Regards
> 
> Marcel
> 
> ------------------------------------------------------- 
> SF.Net <http://SF.Net> email is sponsored by: Discover Easy Linux 
> Migration Strategies
> from IBM. Find simple to follow Roadmaps, straightforward articles,
> informative Webcasts and more! Get everything you need to get up to 
> speed, fast. http://ads.osdn.com/?ad_idt77&alloc_id\x16492&opclick<http://ads.osdn.com/?ad_idt77&alloc_id%16492&opclick>
> _______________________________________________
> Bluez-users mailing list 
> Bluez-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-users 
>

[-- Attachment #2: Type: text/html, Size: 2596 bytes --]