Recent applications of Privacy Enhancing Technologies (PETs) reveal a paradox. PETs aim to alleviate power asymmetries, but can actually entrench the infrastructural power of companies implementing them vis-\`a-vis other public and private organisations. We investigate whether and how this contradiction manifests with an empirical study of Amazon's cloud connectivity service called Sidewalk. In 2021, Amazon remotely updated Echo and Ring devices in consumers' homes, to transform them into Sidewalk "gateways". Compatible Internet of Things (IoT) devices, called "endpoints", can connect to an associated "Application Server" in Amazon Web Services (AWS) through these gateways. We find that Sidewalk is not just a connectivity service, but an extension of Amazon's cloud infrastructure as a software production environment for IoT manufacturers. PETs play a prominent role in this pursuit: we observe a two-faceted PET paradox. First, suppressing some information flows allows Amazon to promise narrow privacy guarantees to owners of Echo and Ring devices when "flipping" them into gateways. Once flipped, these gateways constitute a crowdsourced connectivity infrastructure that covers 90% of the US population and expands their AWS offerings. We show how novel information flows, enabled by Sidewalk connectivity, raise greater surveillance and competition concerns. Second, Amazon governs the implementation of these PETs, requiring manufacturers to adjust their device hardware, operating system and software; cloud use; factory lines; and organisational processes. Together, these changes turn manufacturers' endpoints into accessories of Amazon's computational infrastructure; further entrenching Amazon's infrastructural power. We argue that power analyses undergirding PET design should go beyond analysing information flows. We propose future steps for policy and tech research.

翻译：隐私增强技术（PETs）的最新应用揭示了一个悖论。PETs旨在缓解权力不对称，却可能实际上巩固实施这些技术的公司相对于其他公共和私人组织的基础设施权力。我们通过对亚马逊名为Sidewalk的云连接服务进行实证研究，探讨这一矛盾是否及如何显现。2021年，亚马逊远程更新了消费者家中的Echo和Ring设备，将其转变为Sidewalk"网关"。兼容的物联网（IoT）设备（称为"终端"）可通过这些网关连接到亚马逊网络服务（AWS）中的关联"应用服务器"。我们发现Sidewalk不仅是连接服务，更是亚马逊云基础设施作为物联网制造商软件生产环境的延伸。PETs在此过程中发挥着突出作用：我们观察到双重维度的PET悖论。首先，抑制某些信息流使亚马逊能够在将Echo和Ring设备"转换"为网关时，向设备所有者承诺有限的隐私保障。一旦完成转换，这些网关便构成覆盖美国90%人口的众包连接基础设施，并扩展了其AWS服务。我们展示了Sidewalk连接所催生的新型信息流如何引发更严重的监控与竞争担忧。其次，亚马逊主导这些PETs的实施，要求制造商调整其设备硬件、操作系统与软件、云端使用、生产线及组织流程。这些改变共同将制造商的终端设备转变为亚马逊计算基础设施的附属品，进一步巩固了亚马逊的基础设施权力。我们认为支撑PET设计的权力分析应超越信息流分析范畴，并为政策与技术研究提出未来发展方向。