Private, end-to-end encrypted conversations are coming to Skype courtesy of Signal, the secure messaging technology and app from Open Whisper Systems.
Powered by the open source Signal Protocol, the Signal mobile app fully encrypts data, allowing users to send text-based messages, videos and audio while thwarting third-party attempts to snoop on their communications. The protocol is also being used by Facebook, Google and WhatsApp to shore up user privacy.
Open Whisper Systems' technology is also found in the Haven app for Android devices.
Built by the Guardian Project and the Freedom of the Press Foundation, Haven uses the sensors in Android phones to unmask potential surveillance risks and uses a secure software library to protect communications on the Signal messaging service. National Security Agency whistleblower Edward Snowden serves as president of the Freedom of the Press Foundation, a nonprofit organization dedicated to supporting journalists and whistle-blowers.
Now, Microsoft’s Skype is joining the pack.
"At Signal, our goal is to make private communication simple and ubiquitous," wrote Open Whisper Systems representative Joshua Lund, in a Jan. 11 blog post, concerning the collaboration. "With hundreds of millions of active users, Skype is one of the most popular applications in the world, and we’re excited that Private Conversations in Skype will allow more users to take advantage of Signal Protocol’s strong encryption properties for secure communication."
For now, the Private Conversations feature is only available to users who are enrolled in the Skype Insiders early access and feedback program.
With the added security come some restrictions on how many participants can take part in an encrypted conversation and which functionality can be used. "Skype Private Conversations give you enhanced security through end-to-end encryption with an additional layer of security for conversations between you and your friends and family," states an online support document from Microsoft.
"Private Conversations can only be between you and one other contact. This is not supported in groups," cautions the support document.
To get started, users select the New Private Conversation option from the "plus sign" (+) icon and pick a contact. This creates a new chat and prompts the service to send an invitation to the selected contact. Invitations are valid for up to seven days, after which unaccepted invitations must be re-sent.
After both parties agree, private Skype conversations are locked to the specific devices used to start a chat. Users can’t switch another PC or device in mid-conversation. To move a conversation to another device, users must resend an invitation, instructs Microsoft. In the Skype interface a Private Conversations is denoted as a lock icon next to a contact's name.
There are also limitations on the type of content that can be traded over a Private Conversation. According to Microsoft, the feature only supports files, audio messages and emoticons in the chat window. Messages cannot be edited after they are sent, nor can the app be used to forward files users receive through the service.
Like regular chats, Private Conversations can be deleted. Restoring them requires that users start another encrypted chat involving the original participants. If users elect to end a private conversation instead, they must send a new invitation to reopen the lines of highly-secure communications.