Re: [PATCH v2 1/2] Add support for DTLS-SRTP profile negotiation (RFC 5764)

[Martin Storsjö]

On Thu, 1 Nov 2012, Martin Storsjö wrote:

> On Thu, 1 Nov 2012, Nikos Mavrogiannopoulos wrote:
>
> > Is the key size fixed for each profile? If yes, then wouldn't be easier
> > to have a helper function to extract the key, based on the negotiated
> > profile?
>
> Yes, the master key size should be 128 bit and the master salt size 112 bit,

To clarify, this is the case for both the AES128_CM and NULL modes - in 
the NULL cipher mode, the packets still have HMAC-SHA1 authentication, and 
the master key and salt are required for deriving the key to the HMAC.

// Martin