Srtp Key Management Over Voip

Friends,
I am using srtp in voip setup from router to router. I just enter command "srtp" in voice service voip mode and srtp start encrypting/decrypting data that i can see with debug command. But my question is how i can define shared key, encryption means key management?
I tried to find it on cisco website but couldn't. My voip setup consist of MD110 pbx with cisco 3800 routers.
Your immediate response will be highly appreciated.


Best Regards

I believe the key that is generated for srtp is randomly generated for each call. Essentially; when the invite is sent from the caller, it contains the key to use to decrypt its encrypted rtp media, and when the 200OK is received by the callee it contains the the key to decrypt its rtp media, and this key is different for each call. What it uses to generate the key probably is random on the cisco box, but I am not exactly sure -- I know with the product that I previously worked on it would randomly generate a key based upon a 128bit random character.

Side issue not answering your question, but just a thought:-

Quote:

router to router

Any reason to not just use ipsec ?