Skype will use the Signal protocol, also used in WhatsApp, Facebook Messenger, and others. Skype does already offer some degree of encryption that protects the communication channel itself. But end-to-end encryption is more secure. It means the contents of messages can only be read by the sender and recipient; they don’t just sit around on Microsoft’s servers. That doesn’t mean this data can’t be intercepted in other ways, of course, but it’s still more secure than most methods of online chat.
The newest Skype preview now supports the Signal protocol: the end-to-end encrypted protocol already used by WhatsApp, Facebook Messenger, Google Allo, and, of course, Signal. Skype Private Conversations will support text, audio calls, and file transfers, with end-to-end encryption that Microsoft, Signal, and, it’s believed, law enforcement agencies cannot eavesdrop on.
You still have to decide if you trust Microsoft with your metadata, but that’s a decision you have to make with every encrypted communications service
In the mid-2000s, Skype was known as a secure and private option for online audio calls and chat, because it incorporated strong encryption and a decentralized peer-to-peer network. But in the early 2010s, after Microsoft purchased it, observers noticed changes in Skype’s architecture, and privacy-conscious chatters began avoiding it over concerns that it may allow third-party and government wiretap surveillance.