In this work, we study the interface of the Brazilian e-Voting Machine (BVM) in the context of electromagnetic side-channel threats commonly referred to as TEMPEST attacks. In a TEMPEST attack against video displays, an eavesdropper uses Software-Defined Radios (SDRs) to recover sensitive information by intercepting electromagnetic emanations generated during video signal transmission. We emulate the BVM using a VGA monitor by leveraging publicly available information disclosed by the electoral authority, including technical specifications, operational rules of the system, and the official BVM interface. Based on this setup, we investigate whether the BVM interface gives rise to a distinctive spectral signature observable through its unintended electromagnetic emissions. Our findings show that design characteristics relevant to a nationwide electoral process -- such as high image contrast, minimal on-screen information, and the prohibition of other electronic devices within the polling station -- result in a simple and highly distinctive spectral signature that can be observed even through a wall in our experiments. Although our experiments do not involve actual BVM hardware, the results raise concerns regarding the system's susceptibility to TEMPEST attacks and highlight the need for further research on protective countermeasures. In this context, our findings may support the design of automatic jammers capable of adaptively targeting compromising frequencies. To the best of our knowledge, this is the first study investigating TEMPEST attacks in the context of an electronic voting system officially adopted by a country.

翻译：本研究以巴西电子投票机（BVM）的接口为对象，探讨电磁侧信道威胁（通常称为TEMPEST攻击）的相关问题。在针对视频显示器的TEMPEST攻击中，窃听者利用软件定义无线电（SDR）通过截获视频信号传输过程中产生的电磁辐射来恢复敏感信息。我们借助选举机构公开的技术规格、系统运行规则及官方BVM接口设计等公开信息，使用VGA显示器模拟了BVM。基于该实验设置，我们研究了BVM接口是否会在其非故意电磁辐射中产生独特的频谱特征。研究结果表明，与全国性选举流程相关的设计特性——例如高图像对比度、屏幕信息最小化以及投票站内禁止使用其他电子设备——导致产生了简单且高度独特的频谱特征，即使隔墙实验也能观测到该特征。虽然我们的实验未涉及真实BVM硬件，但结果引发了对该系统易受TEMPEST攻击的担忧，并突显了进一步研究防护对策的必要性。在此背景下，我们的发现可能有助于设计能够自适应瞄准泄密频率的自动干扰器。据我们所知，这是首个针对国家正式采用的电子投票系统中的TEMPEST攻击开展的研究。