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Use of mobile phones today has become pervasive throughout society. A common use of a phone involves calling another person using VoIP apps. However the OSes on mobile devices are prone to compromise creating a risk for users who want to have private conversations when calling someone. Mobile devices today provide a hardware-protected mode called trusted execution environment (TEE) to protect users from a compromised OS. In this paper we propose a design to allow a user to make a secure end-to-end protected VoIP call from a compromised mobile phone. We implemented our design, TruzCall using Android OS and TrustZone TEE running OP-TEE OS. We built a prototype using the TrustZone-enabled Hikey development board and tested our design using the open source VoIP app Linphone. Our testing utilizes a simulation based environment that allows a Hikey board to use a real phone for audio hardware. 

When OS and hypervisor are compromised, mobile devices currently provide a hardware protected mode called Trusted Execution Environment (TEE) to guarantee the confidentiality and integrity of the User Interface (UI). The present TEE UI solutions adopt a self-contained design model, which provides a fully functional UI stack in the TEE, but they fail to manage one critical design principle of TEE: a small Trusted Computing Base (TCB), which should be more easily verified in comparison to a rich OS. The TCB size of the self-contained model is large as a result of the size of an individual UI stack. To reduce the TCB size of the TEE UI solution, we proposed a novel TEE UI design model called delegation model. To be specific, our design reuses the majority of the rich OS UI stack. Unlike the existing UI solutions protecting 3-dimensional UI processing in the TEE, our design protects the UI solely as a 2-dimensional surface and thus reduces the TCB size. Our system, called TruZ-View, allows application developers to use the rich OS UI development environment to develop TEE UI with consistent UI looks across the TEE and the rich OS.We successfully implemented our design on HiKey board. Moreover, we developed several TEE UI use cases to protect the confidentiality and integrity of UI. We performed a thorough security analysis to prove the security of the delegation UI model. Our real-world application evaluation shows that developers can leverage our TEE UI with few changes to the existing app’s UI logic. CCS CONCEPTS 

Applications use SQLite databases for storing data such as fitness/health information, contacts, text messages, calendar among others. Such information is sensitive and worth protecting. SQLite engine do not have built-in security to protect databases, rather, it relies on its environment such as the operating system to provide security for database content. While Android provides security mechanisms for SQLite databases, it has been shown to be inadequate. Proposed solutions are not able to protect sensitive database content when the OS is compromised. Also, some existing solutions fall short in protecting sensitive data if the SQLite database file is relocated to an environment that do not have any security restrictions. We propose a hardware isolation solution, leveraging ARM’s TrustZone to protect sensitive content of databases. We design and implement a prototype system on Hikey development board to demonstrate that TrustZone can be integrated with Android to protect SQLite data. Evaluation results shows our system is practical in and do not break the design patterns in Android application development. 

Mobile devices today provide a hardware-protected mode called Trusted Execution Environment (TEE) to help protect users from a compromised OS and hypervisor. Today TEE can only be leveraged either by vendor apps or by developers who work with the vendor. Since vendors consider third-party app code untrusted inside the TEE, to allow an app to leverage TEE, app developers have to write the app code in a tailored way to work with the vendor’s SDK. We proposed a novel design to integrate TEE with mobile OS to allow any app to leverage the TEE. Our design incorporates TEE support at the OS level, allowing apps to leverage the TEE without adding app-specific code into the TEE, and while using existing interface to interact with the mobile OS. We implemented our design, called TruZ-Droid, by integrating TrustZone TEE with the Android OS. TruZ-Droid allows apps to leverage the TEE to protect the following: (i) user’s secret input and confirmation, and (ii) sending of user’s secrets to the authorized server. We built a prototype using the TrustZone-enabled HiKey board to evaluate our design. We demonstrated TruZ-Droid’s effectiveness by adding new security features to existing apps to protect user’s sensitive information and attest user’s confirmation. TruZ-Droid’s real-world use case evaluation shows that apps can leverage TrustZone while using existing OS APIs. Our usability study proves that users can correctly interact with TruZ-Droid to protect their security sensitive activities and data.