This paper aims to survey various techniques utilized for content moderation in end-to-end encryption systems. We assess the challenging aspect of content moderation: maintaining a safe platform while assuring user privacy. We study the unique features of some content moderation techniques, such as message franking and perceptual hashing, and highlight their limitations. Currently implemented content moderation techniques violate the goals of end-to-end encrypted messaging to some extent. This has led researchers to develop remediations and design new security primitives to make content moderation compatible with end-to-end encryption systems. We detail these developments, analyze the proposed research efforts, assess their security guarantees, correlate them with other proposed solutions, and determine suitable improvements under specific scenarios.

翻译：本文旨在系统综述端到端加密系统中用于内容审核的各类技术。我们评估了内容审核的挑战性维度：在确保用户隐私的同时维护平台安全。通过研究消息公证与感知哈希等特定内容审核技术的独特特征，着重揭示其局限性。当前实施的内容审核方案在一定程度上背离了端到端加密消息系统的设计目标，这促使研究者开发补救措施并设计新型安全原语，使内容审核机制与端到端加密系统兼容。我们详细阐述这些技术进展，分析相关研究成果，评估其安全保障能力，建立与其他解决方案的关联性，并确定特定场景下的适宜改进方向。