title: Is the SDP a=crypto attribute relevant when DTLS-SRTP is used?
body: <p>The a=crypto attribute in RFC 4568 has a separate section 9.2. for SRTP &quot;Crypto&quot; Attribute Grammar. What it basically includes is a list of attribute values required for encrypting media (crypto suite, method, session params, keys, MKI...).</p>
  <p>However, DTLS-SRTP also does in its handshake protocol (<a href="https://www.rfc-editor.org/rfc/rfc5764" rel="nofollow noreferrer">RFC 5764 - SRTP Extension for DTLS</a>) what is done via SDP in an offer-answer protocol. So, is it correct to say that where DTLS-SRTP is used, the a=crypto: attribute is not used. For example, does webRTC offer-answer SDP use the &quot;a=crypto:&quot; attribute as DTLS-SRTP is a must for webRTC?</p>
  <p>Informational RFC &quot;<a href="https://datatracker.ietf.org/doc/html/draft-ietf-rtcweb-sdp-11" rel="nofollow noreferrer">SDP for webRTC</a>&quot; also does not throw any light on this issue.</p>
  <p>Please clarify.</p>