The feature, called Private Conversations, is available to users on Windows desktop, Android, iOS, Mac, and Linux. When Microsoft started rolling out the tester function in January, the company said that encryption would work for audio and text, as well as image, audio and video file transfer, using the Signal Protocol from Open Whisper Systems.
How to start a private conversation on Skype
- Start a new chat on mobile by tapping the New Chat button, then hit Private Conversation.
- On the desktop, you can do this by clicking on the new Chat+ button, then selecting New Private Conversation.
- Next, choose the contact you want to start the conversation with. They'll get an invitation, which will be valid for seven days. It'll expire if they don't accept by then, and then you'll have to send a new one.
- After your friend accepts the invite, the private conversation will be available through the device that they accepted your request form. If either of you wants to have the conversation on another device, you'll need to accept an invitation from that device.
- You can switch between a Skype and private conversation by hitting the Skype or Private tabs up at the top.
- You'll also be able to start a private conversation with someone you're already talking to by selecting New Private Conversation from their profile.
How to start a private call
- Start a new private conversation or select one that already exists.
- Turn on the Private tab at the top of the conversation.
- Select the Private Call button.
How to End a private conversation
- Click on the chat header.
- Go to Chat settings.
- Select End private conversation.
- From that window, hit End conversation. If you want to start another private conversation with that person, send them another invite.
How to delete a private conversation
- Click on the chat heading.
- Go to Chat Settings
- Select Delete Private Conversation.
- From this window, tap Delete. This will delete messages in that conversation from your device.
There are certain restrictions on private calls. You will not be able to edit a message or forward a file. Previews of private conversations also won't show up in your chats list or notifications, for additional privacy.
Skype has previously offered 256-bit AES encryption, but end-to-end encryption is more secure since the contents of messages can only be read by the sender and recipient. It joins the ranks of other chat platforms that offer end-to-end encryption, including Apple’s iMessage and Facebook’s Messenger, which also offers the feature as an opt-in.