Asterisk-SRTP-Minisip

[Mikael Magnusson]

Emanuele Bottegoni wrote:
> Hello,
> 
> I'm thinking about a topic previously discussed with Mikael. Asterisk
> is like as B2BUA and modifies SDP messages to forward to the
> other endpoint.
> A question: With the SRTP patch installed is possible to work well
> with device have sdescriptions or only with Minisip?

It works with both MIKEY (supported by Minisip) and sdescriptions
(tested with Snom softphone).

> Because I've tried with Phonerlite but not encryption seems realized.

Phonerlite is working with the patch for me. Have you enabled SRTP in
the codec dialog?

> The second one is:I don't understant the meaning of "bridging" not
> supported yet by SRTP patch.

Bridging is supported but not native bridging, i.e. using SIP reINVITE
to remove Asterisk from the media path and have the media sent directly
between the two devices.

> Using SRTP patch Asterisk decrypt and then encrypt the media packets?

Yes, if you connect two channels which both use SRTP, then Asterisk will
remain in the middle decrypting and encrypting each SRTP packet.

> BUt in a normal SIP session,once authentication is performed, the
client communicates directly
> with the other client, don't go through the server. If all voice
packets cross the server there's
> an high computational load. > Please explain me well.
> 
> Emanuele 

Yes, and I think the patch can be inproved and support native bridging
for some SRTP calls, at least between two legs which use sdescriptions.

Mikael