By default the library will support remote sdp with srtp offer, so by default if remote party offers srtp it will do the same.
But there are two more APIs in the SipAccountData class to set the SRTP use mode and SRT signalling mode https://trac.pjsip.org/repos/wiki/SRTP#UsingSRTPinPJSUA-LIB
To allow secure signalling modes 1 and 2 the TLS transport is loaded by default in the endpoint.
By default the library will support remote sdp with srtp offer, so by default if remote party offers srtp it will do the same. But there are two more APIs in the SipAccountData class to set the SRTP use mode and SRT signalling mode https://trac.pjsip.org/repos/wiki/SRTP#UsingSRTPinPJSUA-LIB
To allow secure signalling modes 1 and 2 the TLS transport is loaded by default in the endpoint.