Cryptanalysis on End-to-End Encryption Schemes of Communication Tools and Its Research Trend.

This paper summarizes our cryptanalysis results on real-world End-to-End Encryption (E2EE) schemes published in recent years. Our targets are LINE (a major messaging application), SFrame (an E2EE protocol adopted by major video/audio applications), and Zoom (a major video communication application). For LINE, we show several attacks against the message integrity of Letter Sealing, the E2EE protocol of LINE, that allow forgery and impersonation. For SFrame, we reveal a critical issue that leads to an impersonation (forgery) attack by a malicious group member with a practical complexity. For Zoom, we discover several attacks more powerful than those expected by Zoom according to their whitepaper. Specifically, if insiders collude with meeting participants, they can impersonate any Zoom user in target meetings, whereas Zoom indicates that they can impersonate only the current meeting participants. We also describe several important works in the area of E2EE security research.