End-to-End Encryption (E2EE) is a cornerstone of modern-day instant messaging systems. Diffie–Hellman key exchange seems to be the very basis of these systems and Double Ratchet Algorithm is based on it. Diffie-Hellman can provide Forward secrecy.
Examples of instant messaging systems that offer E2EE are as follows:
- Signal Protocol – originally produced Double Rachet Algorithm; adopted by Whatsapp, Facebook Chat, Google’s RCS, Skype, etc., although E2EE is not turned on by default
- Matrix (protocol) – federated
- Telegram (software)
- Line (software)
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