New USENIX Paper Achieves True Messenger Privacy via Math, Hiding Recipients from Server

matthew_d_green · x · 2026-08-12

Most "private" messengers only hide message content; the server still knows who is talking to whom. A new USENIX Security paper proposes a mathematical solution where the server updates every user's encrypted inbox identically. Only the correct recipient's inbox changes internally, preventing the server from knowing the actual recipient.

This privacy is guaranteed by maths rather than platform policies. The trade-off is a significant computational overhead, requiring about 1.6 seconds of compute per message.

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