Secure messaging applications often offer privacy to users by protecting their messages from would be observers through end-to-end encryption techniques. However, the metadata of who communicates with whom cannot be concealed by encryption alone. Signal's Sealed Sender mechanism attempts to enhance its protection of this data by obfuscating the sender of any message sent with the protocol. However, it was shown by Martiny et al. that due to the message delivery protocols in Signal, the record of who receives messages can be enough to recover this metadata. In this work we extend the attack presented from deanonymizing communicating pairs to deanonymizing entire group conversations.

翻译：安全消息应用常通过端到端加密技术保护用户消息免受潜在观察者窥探，从而为用户提供隐私保障。然而，仅凭加密无法隐藏“谁与谁通信”的元数据。Signal 的“密封发送者”机制旨在通过混淆协议中发送消息者的身份来增强对此类数据的保护。但 Martiny 等人已证明，由于 Signal 的消息传递协议，接收消息的记录足以恢复该元数据。本研究将此前针对通信对去匿名化的攻击方法扩展至整个群组对话的去匿名化。