[Bluez-users] How to set the encryptions key size?

[Bluez-users] How to set the encryptions key size?

[Koestering, Nina (EXT)]

Hi, 
 
is there a way to specify the encryption key size? Is it possible to
enforce an encryption with a 128-bit key? I found out that there is a
method to get the encryption key size, but I didn't find a way to set
the key size.
Could you please give me some advice? Thanks in advance.
 
Best regards
Nina
 




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Re: [Bluez-users] How to set the encryptions key size?

[Marcel Holtmann]

Hi Nina,

> is there a way to specify the encryption key size? Is it possible to
> enforce an encryption with a 128-bit key? I found out that there is a
> method to get the encryption key size, but I didn't find a way to set
> the key size.

the encryption key size can vary between 8-bit and 128-bit. Some chips
have a limited encryption key size of 56-bit, because of export
regulations in some country. For example for CSR chips you can use the
command "hciconfig hci0 revision" as root to check for the maximal
encryption key size.

In general the encryption key size is not changeable. However with chips
from CSR you can specify a range for it. Having a lower encryption key
size of 40-bit renders most devices useless, because the other side
won't accept any connection anymore.

So if your device has a maximum limit of 56-bit, this limit will be
hardcoded into the firmware in most cases and thus not changeable.

However the method to read the encryption key size of a piconet is
vendor specific. The Bluetooth SIG refuses to add a standard HCI command
for this task.

Regards

Marcel



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Re: [Bluez-users] How to set the encryptions key size?

[Koestering, Nina (EXT)]

Hi Marcel,

thanks for the fast answer. 
How can I specify the range of the encryption key size for the CSR chip?
I want to enforce an encryption key of 128 bit and both sides support
the 128-bit encryption.

Best regards
Nina

> -----Original Message-----
> From: bluez-users-bounces@lists.sourceforge.net 
> [mailto:bluez-users-bounces@lists.sourceforge.net] On Behalf 
> Of Marcel Holtmann
> Sent: Monday, March 19, 2007 4:03 PM
> To: BlueZ users
> Subject: Re: [Bluez-users] How to set the encryptions key size?
> 
> Hi Nina,
> 
> > is there a way to specify the encryption key size? Is it possible to
> > enforce an encryption with a 128-bit key? I found out that 
> there is a
> > method to get the encryption key size, but I didn't find a 
> way to set
> > the key size.
> 
> the encryption key size can vary between 8-bit and 128-bit. Some chips
> have a limited encryption key size of 56-bit, because of export
> regulations in some country. For example for CSR chips you can use the
> command "hciconfig hci0 revision" as root to check for the maximal
> encryption key size.
> 
> In general the encryption key size is not changeable. However 
> with chips
> from CSR you can specify a range for it. Having a lower encryption key
> size of 40-bit renders most devices useless, because the other side
> won't accept any connection anymore.
> 
> So if your device has a maximum limit of 56-bit, this limit will be
> hardcoded into the firmware in most cases and thus not changeable.
> 
> However the method to read the encryption key size of a piconet is
> vendor specific. The Bluetooth SIG refuses to add a standard 
> HCI command
> for this task.
> 
> Regards
> 
> Marcel
> 
> 
> 
> --------------------------------------------------------------
> -----------
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> 

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Re: [Bluez-users] How to set the encryptions key size?

[Marcel Holtmann]

Hi Nina,

> How can I specify the range of the encryption key size for the CSR chip?
> I want to enforce an encryption key of 128 bit and both sides support
> the 128-bit encryption.

first of all you need a firmware that support 128-bit keys. And then you
can use the bccmd command to set the PS key for keymin and keymax to
128-bit. Check the pskeys.txt of your firmware or the CSR documentation
for more details.

Regards

Marcel



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