Skype is the latest messaging service to jump onto the end-to-end encryption bandwagon. The Microsoft-owned service has partnered up with Signal in order to enable the new functionality, which is optional and not default for every chat. Thus, Skype's implementation is similar to what Facebook Messenger uses, which has dedicated Secret Conversations you can set up for this purpose. Skype's version is called Private Conversations, and these aren't supported for groups. To start a Private Conversation, you tap or click the "+" icon, then select the self-descriptive New Private Conversation...
Source: https://www.gsmarena.com/skype_adds_private_conversations_with_endtoend_encryption-news-29113.php
