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：本文旨在综述端到端加密系统中用于内容审核的各种技术。我们评估了内容审核面临的挑战：在确保用户隐私的同时维护平台安全。我们研究了部分内容审核技术（如消息标记和感知哈希）的独特特性，并指出其局限性。当前已实施的内容审核技术在一定程度上违背了端到端加密通信的目标。这促使研究者开发补救措施并设计新的安全原语，以使内容审核与端到端加密系统相兼容。我们详细阐述了这些进展，分析了相关研究提案，评估其安全保障机制，将其与其他解决方案进行关联比较，并确定了特定场景下的适用性改进方案。