[sr-dev] TLS key recommendation

[Olle E. Johansson]

13 okt 2009 kl. 13.23 skrev Andrei Pelinescu-Onciul:

> On Oct 13, 2009 at 12:57, Henning Westerholt <henning.westerholt at 1und1.de 
> > wrote:
>> On Samstag, 10. Oktober 2009, Olle E. Johansson wrote:
>>> "
>>>    Try to avoid using keys larger then 1024 bytes. Large keys
>>> significantly slow down the TLS connection handshake, thus limiting
>>> the maximum SIP-router TLS connection rate.
>>> "
>>>
>>> Is this still a valid recommendation? Based on which size of CPU/ 
>>> system?
>>
>> Hi Olle,
>>
>> i'd think that today we should suggest a larger key. I've found  
>> this page:
>> http://www.keylength.com/en/compare/
>>
>> according to it newer sources suggest a value of at least 1536 bits  
>> for
>> asymmetric keys.
>
>
> IMHO 1024 keys are more then enough for normal SIP trafic.
>
> The recommandation of using smaller keys is still valid. Even on  
> modern
> system encryption will eat a lot of CPU, and if you need to support
> several hundreds encrypted connections in the same time you'll quickly
> run into problems.

Well, one has to consider when these keys are used. It's not for  
encryption of SIP traffic at all.
The keys are used to authenticate and to do key exchange. The actual  
encryption is done
with much weaker keys.

I personally think this is an old recommendation, but have nothing  
against keeping it at this point.
I'll just reserve the right to come back after X*Y months about it  
when we have more CPU in the default server ;-)

/O :-)