In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
-Signatures generated according to the signature generation algorithm might be subject to replay attacks. However, inclusion of the XMPP "from" and "to" addresses limits these attacks to compromised servers or client-to-server connections. In addition, inclusion of the nonce value also helps to prevent replay attacks.