Exploiting Security Side Channels in E2E Encrypted Messengers
Discloses network and timing side channels in end-to-end encrypted messaging apps that allow adversaries to reconstruct contact graphs and user activity.
Summary
End-to-End Encryption and Residual Metadata
Modern messaging apps (such as Signal, WhatsApp, and Telegram) use robust end-to-end encryption to protect message contents. However, network-level and application-level side channels frequently leak metadata.
Analyzing Network Traffic and Typing Notifications
G Gegenheuber and M Gunther analyze packet timing, size distributions, and ephemeral feature handshakes (such as typing indicators and read receipts) across popular encrypted messengers.
Reconstructing User Contact Graphs and Activity
By monitoring passive network flows or sending probe packets, an adversary can determine when specific users are communicating, infer recipient identities, and reconstruct detailed social graphs without breaking cryptographic ciphers.
Mitigation Strategies for Encrypted Protocols
Eliminating metadata leakage requires implementing constant-rate packet padding, decoupling typing notifications from network broadcasts, and routing telemetry through mixnets.
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