TWC: Small: Techniques and Tools for Enforcing Proximity-based Policies in Wireless Systems

随着无线技术的普及，设备验证其他设备的位置变得越来越重要。例如，拥有植入式医疗设备（IMD）的患者可能合理地期望，用于控制其植入式医疗设备的任何设备都必须在手臂可及的范围内，以帮助防止未经授权的访问其设备。换句话说，imd应该根据无线连接设备的接近程度（通常是位置）执行策略。在许多应用领域都存在类似的例子：非接触式支付终端可能需要将信用卡放置在终端前面；无线路由器可能要求网络用户位于同一建筑物内；GPS设备可能需要来自卫星的信号（而不是来自伪装成卫星的对手）；移动电话可能需要信号来自已知的、合法的手机信号塔位置。因此，许多无线设备的安全性可以通过在远程设备的位置上实施基于接近度的策略来提高。本项目旨在解决这样一个问题，即尽管执行邻近策略可以提高许多无线设备的安全性，但目前还不存在执行此类策略的可靠技术和工具。该项目通过创建这样的技术和工具来解决这个问题。近距离身份验证技术将允许设备被动地验证远程设备的位置，而无需向远程设备发送消息或与远程设备共享秘密。它们通过利用多径效应来识别远程目标的距离，其中发射器发送的无线信号沿着反射，衍射和散射的多条路径传播到空中的接收器。基于在这些延长路径上传播的无线信号副本的幅度比来做出接近认证决策。邻近策略实施工具将包括(1)用于指定远程设备位置策略的表达性语言和图形界面，(2)用于静态分析指定位置策略的引擎，以便通知安全工程师他们的策略可以执行得多准确以及他们的策略是否令人满意。(3)编译模块，将有效的策略转换为具体的执行代码，该代码可以内联或以其他方式连接到设备的现有连接建立代码中。

As wireless technologies become more pervasive, it becomes increasingly important for devices to authenticate the locations of other devices. For example, patients with implantable medical devices (IMDs) may reasonably expect that any device used to control their IMD would have to be within arm's reach, to help prevent unauthorized access to their device. In other words, IMDs should enforce policies based on the proximity, and in general the location, of wirelessly connected devices. Similar examples exist in many application areas: contactless payment terminals may require credit cards to be located in front of the terminals; wireless routers may require network users to be located in the same building; GPS devices may require signals to come from satellites (rather than from adversaries masquerading as satellites); and mobile phones may require signals to come from known, legitimate cell-tower locations. Hence, the security of many wireless devices could be improved by enforcing proximity-based policies on remote devices' locations.This project aims to address the problem that, although proximity-policy enforcement would improve the security of many wireless devices, robust techniques and tools do not yet exist for enforcing such policies. The project addresses this problem by creating such techniques and tools. The proximity-authentication techniques will allow a device to passively authenticate the location of remote device, without having to send messages to, or share secrets with, the remote device. They identify the proximity of a remote target by utilizing the multipath effect, in which a wireless signal sent by a transmitter propagates to the receiver in the air along multiple paths due to reflection, diffraction, and scattering. The proximity authentication decision is made based on amplitude ratios of wireless signal copies traveling on these prorogation paths. The proximity-policy enforcement tools will include (1) an expressive language, and a graphical interface, for specifying remote-device location policies, (2) an engine for statically analyzing specified location policies, in order to notify security engineers as to how accurately their policies can be enforced and whether their policies are unsatisfiable, and (3) a compilation module to transform valid policies into concrete enforcement code that can be inlined or otherwise hooked into a device's existing connection-establishment code.