Voice assistant system (VAS) is a popular technology for users to interact with the Internet and the Internet-of-Things devices. In the VAS, voice queries are linked to users’ accounts, resulting in long-term and continuous profiling at the service provider. In this paper, we propose a VAS anonymizer aiming to mix the queries of the VAS users to increase the source anonymity. The VAS anonymizer is equipped with a pattern-matching scheme, which allows VAS devices to find effective peer relays without disclosing their query patterns. Furthermore, the VAS anonymizer is equipped with anonymity evaluation modules for evaluating real-time single query, thus reducing the risk of pattern violation at the relays. Both the requester and the relay will evaluate the real-time query based on the resulting anonymity. Only if the anonymity evaluations at both requester and relay are positive, the query will be sent to the service provider via the relay. The VAS anonymizers at VAS devices coordinate the query uploading such that the sources of the queries are anonymized, and the service provider is unable to link the voice queries to individual users. In the experiments using our customized VAS devices and the Amazon Cloud servers, the computation and communication overhead of the matching scheme is shown to be efficient, and the anonymity evaluation modules are shown to be effective in protecting the privacy of the requesters and the relays.

语音助理系统（VAS）是用户与互联网和物联网设备交互的流行技术。在增值服务中，语音查询链接到用户的帐户，从而对服务提供商进行长期、持续的分析。在本文中，我们提出了一种VAS匿名器，旨在混合VAS用户的查询以增加源匿名性。VAS 匿名器配备了模式匹配方案，允许 VAS 设备在不泄露其查询模式的情况下找到有效的对等中继。此外，VAS匿名器配备匿名评估模块，用于评估实时单次查询，从而降低中继处的模式违规风险。请求者和中继者都将根据生成的匿名性来评估实时查询。仅当请求者和中继的匿名评估都是肯定的时，查询才会通过中继发送到服务提供商。VAS设备处的VAS匿名器协调查询上传，使得查询的来源是匿名的，并且服务提供商无法将语音查询链接到个人用户。在使用我们定制的VAS设备和亚马逊云服务器的实验中，匹配方案的计算和通信开销被证明是高效的，并且匿名评估模块被证明可以有效地保护请求者和中继者的隐私。