Microsoft originally started rolling out its end-to-end encrypted Private Conversation capability to testers in January. At that time, officials said this encryption would work for audio calls, text messaging and image, audio and video file transmission using the industry standard Signal Protocol from Open Whisper Systems.
As was the case during the test period, the Private Conversation feature only works for a single conversation per device at a time. But the feature does work on all Skype consumer variants -- Windows Desktop, iOS, Mac, Android and Linux.
Update (August 22): Private Conversation is not enabled in the UWP/Microsoft Store version of Skype and Microsoft is not commenting on when it will be.
To use Private Conversation, users can select that option from a recipient's profile or the compose menu in order to generate an invitation. During that conversation, calls, messages and image/audio/video transmissions are encrypted until the session is ended.
Microsoft has been touting Skype as being encrypted for some time, noting it uses 256-bit AES encryption. But this isn't the same as end-to-end encryption. End-to-end encryption means not just the communication channel is secure but the messages stored on servers can only be read by those involved in the communications.
In other Skype news, Microsoft is testing a new "SMS Connect" feature that will allow users to send and receive SMS messages from the Skype app on their PCs or Macs, as reported last week by WindowsCentral.com (via Windows Blog Italia). The setting for turning on SMS Connect could be seen in Skype Preview on Android last week.