Meta’s Messenger and Instagram Direct use the Signal Protocol for end-to-end encryption of messages, media, and calls. It secures one-on-one and group chats by creating device-specific sessions using ephemeral keys, ensuring message keys change per message for forward secrecy. Group chats use server-side fanout and “Sender Keys” to efficiently encrypt messages. Voice and video calls use separate ephemeral sessions and SFrame for group calls. Media files are encrypted before upload, and key verification helps users detect tampering. Abuse reporting uses cryptographic tagging while preserving privacy and confidentiality.

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