Security, Performance and Energy Trade-offs of Hardware-assisted Memory Protection Mechanisms

The deployment of large-scale distributed systems, e.g., publish-subscribe platforms, that operate over sensitive data using the infrastructure of public cloud providers, is nowadays heavily hindered by the surging lack of trust toward the cloud operators. Although purely software-based solutions exist to protect the confidentiality of data and the processing itself, such as homomorphic encryption schemes, their performance is far from being practical under real-world workloads. The performance trade-offs of two novel hardware-assisted memory protection mechanisms, namely AMD SEV and Intel SGX - currently available on the market to tackle this problem, are described in this practical experience. Specifically, we implement and evaluate a publish/subscribe use-case and evaluate the impact of the memory protection mechanisms and the resulting performance. This paper reports on the experience gained while building this system, in particular when having to cope with the technical limitations imposed by SEV and SGX. Several trade-offs that provide valuable insights in terms of latency, throughput, processing time and energy requirements are exhibited by means of micro- and macro-benchmarks.Comment: European Commission Project: LEGaTO - Low Energy Toolset for Heterogeneous Computing (EC-H2020-780681

Offline Model Guard: Secure and Private ML on Mobile Devices

Performing machine learning tasks in mobile applications yields a challenging conflict of interest: highly sensitive client information (e.g., speech data) should remain private while also the intellectual property of service providers (e.g., model parameters) must be protected. Cryptographic techniques offer secure solutions for this, but have an unacceptable overhead and moreover require frequent network interaction. In this work, we design a practically efficient hardware-based solution. Specifically, we build Offline Model Guard (OMG) to enable privacy-preserving machine learning on the predominant mobile computing platform ARM - even in offline scenarios. By leveraging a trusted execution environment for strict hardware-enforced isolation from other system components, OMG guarantees privacy of client data, secrecy of provided models, and integrity of processing algorithms. Our prototype implementation on an ARM HiKey 960 development board performs privacy-preserving keyword recognition using TensorFlow Lite for Microcontrollers in real time.Comment: Original Publication (in the same form): DATE 202

On Making Emerging Trusted Execution Environments Accessible to Developers

New types of Trusted Execution Environment (TEE) architectures like TrustLite and Intel Software Guard Extensions (SGX) are emerging. They bring new features that can lead to innovative security and privacy solutions. But each new TEE environment comes with its own set of interfaces and programming paradigms, thus raising the barrier for entry for developers who want to make use of these TEEs. In this paper, we motivate the need for realizing standard TEE interfaces on such emerging TEE architectures and show that this exercise is not straightforward. We report on our on-going work in mapping GlobalPlatform standard interfaces to TrustLite and SGX.Comment: Author's version of article to appear in 8th Internation Conference of Trust & Trustworthy Computing, TRUST 2015, Heraklion, Crete, Greece, August 24-26, 201

Proceedings of the Workshop on web applications and secure hardware (WASH 2013).

Web browsers are becoming the platform of choice for applications that need to work across a wide range of different devices, including mobile phones, tablets, PCs, TVs and in-car systems. However, for web applications which require a higher level of assurance, such as online banking, mobile payment, and media distribution (DRM), there are significant security and privacy challenges. A potential solution to some of these problems can be found in the use of secure hardware – such as TPMs, ARM TrustZone, virtualisation and secure elements – but these are rarely accessible to web applications or used by web browsers. The First Workshop on Web Applications and Secure Hardware (WASH'13) focused on how secure hardware could be used to enhance web applications and web browsers to provide functionality such as credential storage, attestation and secure execution. This included challenges in compatibility (supporting the same security features despite different user hardware) as well as multi-device scenarios where a device with hardware mechanisms can help provide assurance for systems without. Also of interest were proposals to enhance existing security mechanisms and protocols, security models where the browser is not trusted by the web application, and enhancements to the browser itself

TWallet ARM TrustZone Enabled Trustable Mobile Wallet: A Case for Cryptocurrency Wallets

With the increasing popularity of Blockchains supporting virtual cryptocurrencies it has become more important to have secure devices supporting operations in trustable cryp- tocurrency wallets. These wallets, currently implemented as mobile Apps or components of mobile Apps must be protected from possible intrusion attacks. ARM TrustZone technology has made available an extension of the ARM processor ar- chitecture, allowing for the isolation of trusted and non-trusted execution environments. Critical components and their runtime support can be "booted" and loaded to run in the isolated execution environment, backed by the ARM processor. The ARM TrustZone solution provides the possible enforcement of security and privacy conditions for applica- tions, ensuring the containment of sensitive software components and data-management facilities, isolating them from OS-level intrusion attacks. The idea is that sensitive compo- nents and managed data are executed with a trust computing base supported at hardware and firmware levels, not affected by intrusions against non-protected OS-level runtime components. In this dissertation we propose TWallet: a solution designed as a generic model to sup- port secure and trustable Mobile Client Wallets (implemented as mobile Apps), backed by the ARM TrustZone technology. The objective is to manage local sensitive stored data and processing components in a trust execution environment isolated from the Android OS. We believe that the proposed TWallet framework model can also inspire other specific solutions that can benefit from the isolation of sensitive components in mobile Android Apps. As a proof-of-concept, we used the TWallet framework model to implement a trusted wallet application used as an Ethereum wallet, to operate with the Ethereum Blockchain. To achieve our goals, we also conducted different experimental observations to analyze and validate the solution, with the implemented wallet integrated, tested and validated with the Rinkeby Ethereum Test Network.Com o aumento da popularidade de Blockchains e utilização de sistemas de criptomoedas, tornou-se cada vez mais importante a utilização de dispositivos seguros para suportar aplicações de carteiras móveis (vulgarmente conhecidas por mobile wallets ou mobile cryptowallets). Estas aplicações permitem aos utilizadores uma gestão local, cómoda, confiável e segura de dados e operações integradas com sistemas de Blockchains. Estas carteiras digitais, como aplicações móveis completas ou como componentes de outras aplicações, têm sido desenvolvidas de forma generalizada para diferentes sistemas operativos convencionais, nomeadamente para o sistema operativo Android e para diferentes sistemas de criptomoedas. As wallets devem permitir processar e armazenar informação sensível associada ao controlo das operações realizadas, incluindo gestão e consulta de saldos de criptomoedas, realização e consultas de históricos de movimentos de transações ou consolidação do estado destas operações integradas com as Blockchains remotas. Devem também garantir o controlo seguro e confiável do processamento criptográfico envolvido, bem como a segurança das respetivas chaves criptográficas utilizadas. A Tecnologia ARM TrustZone disponibiliza um conjunto de extensões para as arquiteturas de processadores ARM, possibilitando o isolamento e execução de código num ambiente de execução suportado ao nível do hardware do próprio processador ARM. Isto possibilita que componentes críticos de aplicações ou de sistemas operativos suportados em processadores ARM, possam executar em ambientes isolados com minimização propiciada pelo isolamento da sua Base de Computação Confiável (ou Trusted Computing Base). A execução em ambiente seguro suportado pela solução TrustZone pode oferecer assim um reforço adicional de propriedades de confiabilidade, segurança e privacidade. Isto possibilita isolar componentes e dados críticos de possíveis ataques ou intrusões ao nível do processamento e gestão de memória ou armazenamento suportados pelo sistema operativo ou bibliotecas middleware, como é usual no caso de aplicações móveis, executando em ambiente Android OS ou noutros sistemas operativos de dispositivos móveis. Nesta dissertação propomos a solução TWallet, uma aproximação genérica para suporte de wallets utilizadas como aplicações móveis confiáveis em ambiente Android OS e fortalecidas pela utilização da tecnologia ARM TrustZone. O objetivo é possibilitar o isolamento de dados e componentes sensíveis deste tipo de aplicações, tornando-as mais seguras e confiáveis. Acreditamos que o modelo de desenho e implementação da solução TWallet, visto como uma framework de referência, poderá também ser utilizada no desenvolvimento de outras aplicações móveis em que o isolamento e segurança de componentes e dados críticos são requisitos semelhantes aos endereçados. Este pode ser o caso de aplicações de pagamento móvel, aplicações bancárias na área de mobile banking ou aplicações de bilhética na área vulgarmente chamada como mobile e-ticketing, entre outras. Como prova de conceito, utilizámos a TWallet framework para implementar um protótipo de uma wallet confiável, suportável em Android OS, para gestão de operações e criptomoedas na Blockchain Ethereum. A implementação foi integrada, testada e validada na rede Rinkeby Test Network - uma rede de desenvolvimento e testes utilizada como primeiro estágio de validação de aplicações e componentes para a rede Ethereum em operação real. Para validação da solução TWallet foi realizada uma avaliação experimen- tal. Esta avaliação envolveu a observação de indicadores de operação com verificação e comparação de diferentes métricas de operação e desempenho, bem como de alocação de recursos da aplicação protegida no modelo TWallet, comparando esses mesmo indicadores com o caso da mesma aplicação sem essa proteção