If you want a freely usable implementation of SRTP look at 
srtp.sourceforge.net.
Regards,
Steve
John Todd wrote:
>
> I have found few VoIP clients that support encryption.  The only one 
> that comes to mind is the Zultys devices (they have a softphone and a 
> hardphone that support SRTP.)  I spoke with them as recently as today, 
> asking if they'd be interested in supplying patches for their 
> AES-based SRTP encryption implementation to Asterisk, and they said 
> that they didn't have the ability to put those patches together at the 
> moment, but they'd be happy testing functionality with their devices 
> and Asterisk once implemented.
>
> Has anyone done any work with SRTP and Asterisk that could become 
> public?  I've still got a number of clients who aren't moving
towards
> VoIP due to security concerns with end-user stations.  There are now 
> quite a few AES-specific files stuffed into the Asterisk distribution, 
> and a quick "grep" doesn't show anything using them.
Hopefully this
> means that we're almost at the edge of making SRTP a reality...