Privacy-enhancing technologies (PETs) have attracted significant attention in response to privacy regulations, driving the development of applications that prioritize user data protection. At the same time, the information and communication technology (ICT) sector faces growing pressure to reduce its environmental footprint, particularly its energy consumption. While numerous studies have assessed the energy consumption of ICT applications, the environmental impact of cryptographic PETs remains largely unexplored. This work investigates this question by measuring the energy consumption increase induced by three PETs compared to their non-private counterparts: TLS, Searchable Encryption, and Fully Homomorphic Encryption (FHE). These technologies were chosen for two reasons. First, they cover different maturity levels -- from the widely deployed TLS protocol to the emerging FHE schemes -- allowing us to examine the influence of maturity on energy consumption. Second, they each have well-established applications in industry: web browsing, encrypted databases, and privacy-preserving machine learning. Our results reveal highly variable energy consumption increases, ranging from 2x for TLS to 10x for Searchable Encryption and 100,000x for FHE. Our experiments demonstrate a simple and reproducible methodology, based on existing open-source software, to quantify the energy costs of PETs. They also highlight the wide spectrum of energy demands across technologies, underscoring the importance of further research on sustainable PET design. Finally, we discuss orthogonal research directions, such as hardware acceleration, to outline promising directions toward sustainable PETs.

翻译：隐私增强技术（PETs）为响应隐私法规而受到广泛关注，推动了优先保护用户数据的应用发展。与此同时，信息与通信技术（ICT）领域面临日益增长的环境足迹削减压力，尤其是能耗问题。尽管已有大量研究评估了ICT应用的能耗，但密码学PETs对环境的影响仍未得到充分探索。本研究通过测量三种PETs相较于非隐私保护方案所引发的能耗增长来探讨这一问题：TLS、可搜索加密与全同态加密（FHE）。选择这些技术基于两点原因：首先，它们覆盖了不同的成熟度层级——从广泛部署的TLS协议到新兴的FHE方案——使我们能够考察成熟度对能耗的影响；其次，它们在工业领域均具有成熟应用场景：网页浏览、加密数据库以及隐私保护机器学习。实验结果表明，能耗增长幅度差异显著：TLS约为2倍，可搜索加密达10倍，而FHE高达100,000倍。本研究基于现有开源软件提出了一种简单可复现的量化PETs能耗成本的方法论。实验结果同时揭示了不同技术间能耗需求的巨大差异，强调了开展可持续PET设计的深入研究的重要性。最后，我们探讨了硬件加速等正交研究方向，以勾勒实现可持续PETs的潜在路径。