Re: [rtcweb] SRTP not mandatory-to-use

[Igor Faynberg <[e-mail]>]

+1 with Eric's comment.

I also see some problems in the original argument.

First of all, as had been pointed to this list a while ago, once there 
is an option to decline security, people will be mislead into doing just 
that.

Second, the VPN argument is flawed in a way additional to what Eric 
pointed: My client and my server may be within the VPN,  while the 
client of my interlocutor does not have to be; then the path outside of 
VPN is exposed.

Third, I don't quite understand the 3G argument.  AKA is used to set up 
keys--and not only for the link layer protection. It is re-used later, 
via GBA, to applicataion layer authentication and session keys. IPsec is 
used in IMS for signaling--not for the voice path, and in any event the 
IPsec tunnel terminates in the network; it is not end-to-end.

Igor

On 12/14/2011 5:32 AM, Eric Rescorla wrote:
> On Wed, Dec 14, 2011 at 3:18 PM, Xavier Marjou<[e-mail]>  wrote:
>> Hi,
>>
>>
>> During the last IETF meeting, there seemed to be many people willing to have
>> SRTP mandatory-to-use in the browser. However, I would like again to
>> underline that in some contexts, it is rather desirable to deactivate, via
>> the WebRTC API, the use of SRTP in order not to encrypt/decrypt at multiple
>> layers.
>>
>>
>> This may be the case in the following example: a company wants to use WebRTC
>> for communications between its co-workers only; the web server and the
>> script using WebRTC API are located on the VPN. In such a case, there is no
>> need to use SRTP. The VPN already provides encryption when needed. If
>> co-workers want to remotely access the VPN, an IPsec tool can already
>> provide the encryption. Furthermore, if they want to remotely access the VPN
>> via a 3G network, there will be encryption at layer 2 using AKA, then IPsec
>> at layer 3, and again at SRTP level if mandatory-to-use.
> I don't understand why this makes SRTP undesirable. What scarce
> resource are you conserving
> here by not using SRTP? As has been noted a number of times, the cost
> of the crypto on
> the endpoints is generally not significant.
>
> Moreover, it's not obvious that even in this setting SRTP doesn't add security
> benefit. Why are you assuming that I want everyone on the same LAN
> as me to be able to listen to my calls, even if they are my co-workers?
>
> -Ekr
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