What are Goals of SRTP

The security goals for SRTP are to ensure:

   - the confidentiality of the RTP and RTCP payloads, and

   - the integrity of the entire RTP and RTCP packets, together with
      protection against replayed packets.

   These security services are optional and independent from each other,
   except that SRTCP integrity protection is mandatory (malicious or
   erroneous alteration of RTCP messages could otherwise disrupt the
   processing of the RTP stream).

   Other, functional, goals for the protocol are:

   - a framework that permits upgrading with new cryptographic
      transforms,

   -  low bandwidth cost, i.e., a framework preserving RTP header
      compression efficiency,

   and, asserted by the pre-defined transforms:

   -  a low computational cost,

   -  a small footprint (i.e., small code size and data memory for
      keying information and replay lists),

   -  limited packet expansion to support the bandwidth economy goal,

   -  independence from the underlying transport, network, and physical
      layers used by RTP, in particular high tolerance to packet loss
      and re-ordering.

   These properties ensure that SRTP is a suitable protection scheme for
   RTP/RTCP in both wired and wireless scenarios.


References:
https://tools.ietf.org/html/rfc3711