For years, Skype has been synonymous with video calling and messaging. However, as the industry moved toward encryption and privacy, Skype usage was discouraged by experts due to its murky encryption. To combat this, Skype has recently introduced end-to-end encryption, and it's now available to the public.
While Skype has almost always been encrypted, privacy-conscious individuals have noticed that since Microsoft acquired the messaging platform, there have been changes to the architecture that allow for third-party access (such as from government wiretaps). However, with Skype's new end-to-end encryption, all messages are now safe from surveillance, whether from Skype or a third party.
Similar to Telegram, end-to-end encryption isn't activated by default. Instead, it is reserved for a special type of conversation, known as Private Conversations.
To start a new private conversation, press the new chat button from the Chats tab. This button is located in the upper-right corner on iOS devices and bottom-right corner on Android.
Once selected, you can initiate Private Conversation in one of two ways. First, long press the contact you wish to securely message and choose "View profile." Select "Start private conversation" to send a request to invite the other party to start an end-to-end encrypted conversation.
The second way is to select "Private conversation" near the top of the screen. This button will bring you to a new list with all eligible contacts — select the contact you wish to message to send them an invitation to start an encrypted conversation.
Once sent, the recipient must accept the invitation. After they accept it, end-to-end encryption is established and all messages sent and received are protected. Since it's end-to-end encryption, that means the contents of your messages are not viewable by any other party from the time they leave your device, through transit (including Microsoft's servers), and on to the recipient's device.
Once you've started a private conversation, you can select the private call button (a phone with a small padlock above it) to initiate a private call. Only audio calls are supported at this time in private conversation; you cannot video call.
Private conversation is supported on Android, iOS, Windows, macOS, and Linux. So no matter what platforms your friends are using, you no longer need to communicate while remaining susceptible to surveillance. Even better, you can be sure the encryption is secure, as it is based on Signal Protocol by Open Whisper Systems, considered one of the most robust encryption systems available.