This is the excerpt from one of the cisco docs.

With Cisco IOS Secure Multicast, users can enjoy the benefits of encryption of “native IP multicast” traffic within their larger enterprise
environment. Cisco IOS Secure Multicast helps customers extend their reach to all of their corporate IP multicast applications, while providing
enhanced security. Having been tested with many applications and delivered across multiple platforms, Cisco IOS Secure Multicast enhances user
experience and efficiently secures multicast applications. The unique integration between GDOI and IPsec provides a level of trust on the corporate
internal network that is similar to the existing cryptographic techniques. This ability to provide a unique model differentiates Cisco Systems from its competitors.