Soon, your chats on Skype can be just as secure as conversations on Signal, the service used by US Senators. Microsoft is integrating the open source Signal protocol, used by WhatsApp, Google, Facebook and Signal itself, into test versions of Skype as 'Private Conversations' for end-to-end encrypted communications.
There are a few restrictions: You can't turn an existing chat into a Private Conversation, and must start each one by sending a request to one of your contacts. They don't carry over between devices, so if you switch platforms, you'll have to send a whole new request. And finally, Private Conversations are currently available in preview only for Skype Insiders, the service's beta tester community.