In collaboration with Signal, Microsoft is introducing a Private Conversations feature in Skype, powered by Signal Protocol. Facebook Messenger, WhatsApp, and Google Allo already use this technology. The protocol combines the Double Ratchet Algorithm, prekeys, and a triple Diffie–Hellman (3-DH) handshake, and uses Curve25519, AES-256 and HMAC-SHA256 as primitives.
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