Secure Remote Storage of Logs with Search Capabilities

Dissertação de Mestrado em Engenharia InformáticaAlong side with the use of cloud-based services, infrastructure and storage, the use of application logs in business critical applications is a standard practice nowadays. Such application logs must be stored in an accessible manner in order to used whenever needed. The debugging of these applications is a common situation where such access is required. Frequently, part of the information contained in logs records is sensitive. This work proposes a new approach of storing critical logs in a cloud-based storage recurring to searchable encryption, inverted indexing and hash chaining techniques to achieve, in a unified way, the needed privacy, integrity and authenticity while maintaining server side searching capabilities by the logs owner. The designed search algorithm enables conjunctive keywords queries plus a fine-grained search supported by field searching and nested queries, which are essential in the referred use case. To the best of our knowledge, the proposed solution is also the first to introduce a query language that enables complex conjunctive keywords and a fine-grained search backed by field searching and sub queries.A gerac¸ ˜ao de logs em aplicac¸ ˜oes e a sua posterior consulta s˜ao fulcrais para o funcionamento de qualquer neg´ocio ou empresa. Estes logs podem ser usados para eventuais ac¸ ˜oes de auditoria, uma vez que estabelecem uma baseline das operac¸ ˜oes realizadas. Servem igualmente o prop´ osito de identificar erros, facilitar ac¸ ˜oes de debugging e diagnosticar bottlennecks de performance. Tipicamente, a maioria da informac¸ ˜ao contida nesses logs ´e considerada sens´ıvel. Quando estes logs s˜ao armazenados in-house, as considerac¸ ˜oes relacionadas com anonimizac¸ ˜ao, confidencialidade e integridade s˜ao geralmente descartadas. Contudo, com o advento das plataformas cloud e a transic¸ ˜ao quer das aplicac¸ ˜oes quer dos seus logs para estes ecossistemas, processos de logging remotos, seguros e confidenciais surgem como um novo desafio. Adicionalmente, regulac¸ ˜ao como a RGPD, imp˜oe que as instituic¸ ˜oes e empresas garantam o armazenamento seguro dos dados. A forma mais comum de garantir a confidencialidade consiste na utilizac¸ ˜ao de t ´ecnicas criptogr ´aficas para cifrar a totalidade dos dados anteriormente `a sua transfer ˆencia para o servidor remoto. Caso sejam necess´ arias capacidades de pesquisa, a abordagem mais simples ´e a transfer ˆencia de todos os dados cifrados para o lado do cliente, que proceder´a `a sua decifra e pesquisa sobre os dados decifrados. Embora esta abordagem garanta a confidencialidade e privacidade dos dados, rapidamente se torna impratic ´avel com o crescimento normal dos registos de log. Adicionalmente, esta abordagem n˜ao faz uso do potencial total que a cloud tem para oferecer. Com base nesta tem´ atica, esta tese prop˜oe o desenvolvimento de uma soluc¸ ˜ao de armazenamento de logs operacionais de forma confidencial, integra e autˆ entica, fazendo uso das capacidades de armazenamento e computac¸ ˜ao das plataformas cloud. Adicionalmente, a possibilidade de pesquisa sobre os dados ´e mantida. Essa pesquisa ´e realizada server-side diretamente sobre os dados cifrados e sem acesso em momento algum a dados n˜ao cifrados por parte do servidor..

Formally designing and implementing cyber security mechanisms in industrial control networks.

This dissertation describes progress in the state-of-the-art for developing and deploying formally verified cyber security devices in industrial control networks. It begins by detailing the unique struggles that are faced in industrial control networks and why concepts and technologies developed for securing traditional networks might not be appropriate. It uses these unique struggles and examples of contemporary cyber-attacks targeting control systems to argue that progress in securing control systems is best met with formal verification of systems, their specifications, and their security properties. This dissertation then presents a development process and identifies two technologies, TLA+ and seL4, that can be leveraged to produce a high-assurance embedded security device. The method presented in this dissertation takes an informal design of an embedded device that might be found in a control system and 1) formalizes the design within TLA+, 2) creates and mechanically checks a model built from the formal design, and 3) translates the TLA+ design into a component-based architecture of a native seL4 application. The later chapters of this dissertation describe an application of the process to a security preprocessor embedded device that was designed to add security mechanisms to the network communication of an existing control system. The device and its security properties are formally specified in TLA+ in chapter 4, mechanically checked in chapter 5, and finally its native seL4 architecture is implemented in chapter 6. Finally, the conclusions derived from the research are laid out, as well as some possibilities for expanding the presented method in the future

Static Verification of an Implementation of 5G-AKA

Computer-aided cryptography offers a variety of tools that are essential for ensuring the security of cryptographic protocols. These tools can assist in designing the protocol, verifying its correctness during implementation, and detecting potential side-channel attacks. In the functional correctness branch of computer-aided cryptography, program specifications are compared against program behavior using a specification language. JML is a specification language for programs written in Java, and OpenJML is one of the verifiers that can check if a Java program meets its corresponding JML specifications. In this study, we investigate the implementation of 5G-AKA and utilize the JML specification language to write specifications. We then use the OpenJML verifier to check whether the implementation satisfies these specifications, and make necessary changes to ensure that the implementation meets the specifications. Through this process, we perform a detailed analysis and uncover several flaws and bugs in the initial implementation. In other words, our study serves as a proof by construction that an implementation of the 5G-AKA specification can be automatically verified using the JML language. Overall, this study serves as a case study for writing specifications in JML language from multiple documents written in English, highlighting the importance of using computer-aided cryptography tools to ensure the correctness of an implementation of cryptographic protocols

Trusted Execution Development: Designing a Secure, High-Performance Remote Attestation Protocol

Intel Software Guard Extensions (SGX) are a Trusted Execution Environment (TEE) technology that allow programs to protect execution process and data from other processes on the platform. We propose a method to combine SGX attestation with Transport Layer Security (TLS). Doing so will combine guarantees about the program, runtime environment, and machine identity into a normal TLS handshake. We implemented a basic server using SGX/TLS and provide performance details and lessons learned during development

Lessons from Formally Verified Deployed Software Systems (Extended version)

The technology of formal software verification has made spectacular advances, but how much does it actually benefit the development of practical software? Considerable disagreement remains about the practicality of building systems with mechanically-checked proofs of correctness. Is this prospect confined to a few expensive, life-critical projects, or can the idea be applied to a wide segment of the software industry? To help answer this question, the present survey examines a range of projects, in various application areas, that have produced formally verified systems and deployed them for actual use. It considers the technologies used, the form of verification applied, the results obtained, and the lessons that can be drawn for the software industry at large and its ability to benefit from formal verification techniques and tools. Note: a short version of this paper is also available, covering in detail only a subset of the considered systems. The present version is intended for full reference.Comment: arXiv admin note: text overlap with arXiv:1211.6186 by other author

New directions for remote data integrity checking of cloud storage

Cloud storage services allow data owners to outsource their data, and thus reduce their workload and cost in data storage and management. However, most data owners today are still reluctant to outsource their data to the cloud storage providers (CSP), simply because they do not trust the CSPs, and have no confidence that the CSPs will secure their valuable data. This dissertation focuses on Remote Data Checking (RDC), a collection of protocols which can allow a client (data owner) to check the integrity of data outsourced at an untrusted server, and thus to audit whether the server fulfills its contractual obligations. Robustness has not been considered for the dynamic RDCs in the literature. The R-DPDP scheme being designed is the first RDC scheme that provides robustness and, at the same time, supports dynamic data updates, while requiring small, constant, client storage. The main challenge that has to be overcome is to reduce the client-server communication during updates under an adversarial setting. A security analysis for R-DPDP is provided. Single-server RDCs are useful to detect server misbehavior, but do not have provisions to recover damaged data. Thus in practice, they should be extended to a distributed setting, in which the data is stored redundantly at multiple servers. The client can use RDC to check each server and, upon having detected a corrupted server, it can repair this server by retrieving data from healthy servers, so that the reliability level can be maintained. Previously, RDC has been investigated for replication-based and erasure coding-based distributed storage systems. However, RDC has not been investigated for network coding-based distributed storage systems that rely on untrusted servers. RDC-NC is the first RDC scheme for network coding-based distributed storage systems to ensure data remain intact when faced with data corruption, replay, and pollution attacks. Experimental evaluation shows that RDC-NC is inexpensive for both the clients and the servers. The setting considered so far outsources the storage of the data, but the data owner is still heavily involved in the data management process (especially during the repair of damaged data). A new paradigm is proposed, in which the data owner fully outsources both the data storage and the management of the data. In traditional distributed RDC schemes, the repair phase imposes a significant burden on the client, who needs to expend a significant amount of computation and communication, thus, it is very difficult to keep the client lightweight. A new self-repairing concept is developed, in which the servers are responsible to repair the corruption, while the client acts as a lightweight coordinator during repair. To realize this new concept, two novel RDC schemes, RDC-SR and ERDC-SR, are designed for replication-based distributed storage systems, which enable Server-side Repair and minimize the load on the client side. Version control systems (VCS) provide the ability to track and control changes made to the data over time. The changes are usually stored in a VCS repository which, due to its massive size, is often hosted at an untrusted CSP. RDC can be used to address concerns about the untrusted nature of the VCS server by allowing a data owner to periodically check that the server continues to store the data. The RDC-AVCS scheme being designed relies on RDC to ensure all the data versions are retrievable from the untrusted server over time. The RDC-AVCS prototype built on top of Apache SVN only incurs a modest decrease in performance compared to a regular (non-secure) SVN system

Design of a secure architecture for the exchange of biomedical information in m-Health scenarios

El paradigma de m-Salud (salud móvil) aboga por la integración masiva de las más avanzadas tecnologías de comunicación, red móvil y sensores en aplicaciones y sistemas de salud, para fomentar el despliegue de un nuevo modelo de atención clínica centrada en el usuario/paciente. Este modelo tiene por objetivos el empoderamiento de los usuarios en la gestión de su propia salud (p.ej. aumentando sus conocimientos, promocionando estilos de vida saludable y previniendo enfermedades), la prestación de una mejor tele-asistencia sanitaria en el hogar para ancianos y pacientes crónicos y una notable disminución del gasto de los Sistemas de Salud gracias a la reducción del número y la duración de las hospitalizaciones. No obstante, estas ventajas, atribuidas a las aplicaciones de m-Salud, suelen venir acompañadas del requisito de un alto grado de disponibilidad de la información biomédica de sus usuarios para garantizar una alta calidad de servicio, p.ej. fusionar varias señales de un usuario para obtener un diagnóstico más preciso. La consecuencia negativa de cumplir esta demanda es el aumento directo de las superficies potencialmente vulnerables a ataques, lo que sitúa a la seguridad (y a la privacidad) del modelo de m-Salud como factor crítico para su éxito. Como requisito no funcional de las aplicaciones de m-Salud, la seguridad ha recibido menos atención que otros requisitos técnicos que eran más urgentes en etapas de desarrollo previas, tales como la robustez, la eficiencia, la interoperabilidad o la usabilidad. Otro factor importante que ha contribuido a retrasar la implementación de políticas de seguridad sólidas es que garantizar un determinado nivel de seguridad implica unos costes que pueden ser muy relevantes en varias dimensiones, en especial en la económica (p.ej. sobrecostes por la inclusión de hardware extra para la autenticación de usuarios), en el rendimiento (p.ej. reducción de la eficiencia y de la interoperabilidad debido a la integración de elementos de seguridad) y en la usabilidad (p.ej. configuración más complicada de dispositivos y aplicaciones de salud debido a las nuevas opciones de seguridad). Por tanto, las soluciones de seguridad que persigan satisfacer a todos los actores del contexto de m-Salud (usuarios, pacientes, personal médico, personal técnico, legisladores, fabricantes de dispositivos y equipos, etc.) deben ser robustas y al mismo tiempo minimizar sus costes asociados. Esta Tesis detalla una propuesta de seguridad, compuesta por cuatro grandes bloques interconectados, para dotar de seguridad a las arquitecturas de m-Salud con unos costes reducidos. El primer bloque define un esquema global que proporciona unos niveles de seguridad e interoperabilidad acordes con las características de las distintas aplicaciones de m-Salud. Este esquema está compuesto por tres capas diferenciadas, diseñadas a la medidas de los dominios de m-Salud y de sus restricciones, incluyendo medidas de seguridad adecuadas para la defensa contra las amenazas asociadas a sus aplicaciones de m-Salud. El segundo bloque establece la extensión de seguridad de aquellos protocolos estándar que permiten la adquisición, el intercambio y/o la administración de información biomédica -- por tanto, usados por muchas aplicaciones de m-Salud -- pero no reúnen los niveles de seguridad detallados en el esquema previo. Estas extensiones se concretan para los estándares biomédicos ISO/IEEE 11073 PHD y SCP-ECG. El tercer bloque propone nuevas formas de fortalecer la seguridad de los tests biomédicos, que constituyen el elemento esencial de muchas aplicaciones de m-Salud de carácter clínico, mediante codificaciones novedosas. Finalmente el cuarto bloque, que se sitúa en paralelo a los anteriores, selecciona herramientas genéricas de seguridad (elementos de autenticación y criptográficos) cuya integración en los otros bloques resulta idónea, y desarrolla nuevas herramientas de seguridad, basadas en señal -- embedding y keytagging --, para reforzar la protección de los test biomédicos.The paradigm of m-Health (mobile health) advocates for the massive integration of advanced mobile communications, network and sensor technologies in healthcare applications and systems to foster the deployment of a new, user/patient-centered healthcare model enabling the empowerment of users in the management of their health (e.g. by increasing their health literacy, promoting healthy lifestyles and the prevention of diseases), a better home-based healthcare delivery for elderly and chronic patients and important savings for healthcare systems due to the reduction of hospitalizations in number and duration. It is a fact that many m-Health applications demand high availability of biomedical information from their users (for further accurate analysis, e.g. by fusion of various signals) to guarantee high quality of service, which on the other hand entails increasing the potential surfaces for attacks. Therefore, it is not surprising that security (and privacy) is commonly included among the most important barriers for the success of m-Health. As a non-functional requirement for m-Health applications, security has received less attention than other technical issues that were more pressing at earlier development stages, such as reliability, eficiency, interoperability or usability. Another fact that has contributed to delaying the enforcement of robust security policies is that guaranteeing a certain security level implies costs that can be very relevant and that span along diferent dimensions. These include budgeting (e.g. the demand of extra hardware for user authentication), performance (e.g. lower eficiency and interoperability due to the addition of security elements) and usability (e.g. cumbersome configuration of devices and applications due to security options). Therefore, security solutions that aim to satisfy all the stakeholders in the m-Health context (users/patients, medical staff, technical staff, systems and devices manufacturers, regulators, etc.) shall be robust and, at the same time, minimize their associated costs. This Thesis details a proposal, composed of four interrelated blocks, to integrate appropriate levels of security in m-Health architectures in a cost-efcient manner. The first block designes a global scheme that provides different security and interoperability levels accordingto how critical are the m-Health applications to be implemented. This consists ofthree layers tailored to the m-Health domains and their constraints, whose security countermeasures defend against the threats of their associated m-Health applications. Next, the second block addresses the security extension of those standard protocols that enable the acquisition, exchange and/or management of biomedical information | thus, used by many m-Health applications | but do not meet the security levels described in the former scheme. These extensions are materialized for the biomedical standards ISO/IEEE 11073 PHD and SCP-ECG. Then, the third block proposes new ways of enhancing the security of biomedical standards, which are the centerpiece of many clinical m-Health applications, by means of novel codings. Finally the fourth block, with is parallel to the others, selects generic security methods (for user authentication and cryptographic protection) whose integration in the other blocks results optimal, and also develops novel signal-based methods (embedding and keytagging) for strengthening the security of biomedical tests. The layer-based extensions of the standards ISO/IEEE 11073 PHD and SCP-ECG can be considered as robust, cost-eficient and respectful with their original features and contents. The former adds no attributes to its data information model, four new frames to the service model |and extends four with new sub-frames|, and only one new sub-state to the communication model. Furthermore, a lightweight architecture consisting of a personal health device mounting a 9 MHz processor and an aggregator mounting a 1 GHz processor is enough to transmit a 3-lead electrocardiogram in real-time implementing the top security layer. The extra requirements associated to this extension are an initial configuration of the health device and the aggregator, tokens for identification/authentication of users if these devices are to be shared and the implementation of certain IHE profiles in the aggregator to enable the integration of measurements in healthcare systems. As regards to the extension of SCP-ECG, it only adds a new section with selected security elements and syntax in order to protect the rest of file contents and provide proper role-based access control. The overhead introduced in the protected SCP-ECG is typically 2{13 % of the regular file size, and the extra delays to protect a newly generated SCP-ECG file and to access it for interpretation are respectively a 2{10 % and a 5 % of the regular delays. As regards to the signal-based security techniques developed, the embedding method is the basis for the proposal of a generic coding for tests composed of biomedical signals, periodic measurements and contextual information. This has been adjusted and evaluated with electrocardiogram and electroencephalogram-based tests, proving the objective clinical quality of the coded tests, the capacity of the coding-access system to operate in real-time (overall delays of 2 s for electrocardiograms and 3.3 s for electroencephalograms) and its high usability. Despite of the embedding of security and metadata to enable m-Health services, the compression ratios obtained by this coding range from ' 3 in real-time transmission to ' 5 in offline operation. Complementarily, keytagging permits associating information to images (and other signals) by means of keys in a secure and non-distorting fashion, which has been availed to implement security measures such as image authentication, integrity control and location of tampered areas, private captioning with role-based access control, traceability and copyright protection. The tests conducted indicate a remarkable robustness-capacity tradeoff that permits implementing all this measures simultaneously, and the compatibility of keytagging with JPEG2000 compression, maintaining this tradeoff while setting the overall keytagging delay in only ' 120 ms for any image size | evidencing the scalability of this technique. As a general conclusion, it has been demonstrated and illustrated with examples that there are various, complementary and structured manners to contribute in the implementation of suitable security levels for m-Health architectures with a moderate cost in budget, performance, interoperability and usability. The m-Health landscape is evolving permanently along all their dimensions, and this Thesis aims to do so with its security. Furthermore, the lessons learned herein may offer further guidance for the elaboration of more comprehensive and updated security schemes, for the extension of other biomedical standards featuring low emphasis on security or privacy, and for the improvement of the state of the art regarding signal-based protection methods and applications

Towards Effective Masquerade Attack Detection

Data theft has been the main goal of the cybercrime community for many years, and more and more so as the cybercrime community gets more motivated by financial gain establishing a thriving underground economy. Masquerade attacks are a common security problem that is a consequence of identity theft and that is generally motivated by data theft. Such attacks are characterized by a system user illegitimately posing as another legitimate user. Prevention-focused solutions such as access control solutions and Data Loss Prevention tools have failed in preventing these attacks, making detection not a mere desideratum, but rather a necessity. Detecting masqueraders, however, is very hard. Prior work has focused on user command modeling to identify abnormal behavior indicative of impersonation. These approaches suffered from high miss and false positive rates. None of these approaches could be packaged into an easily-deployable, privacy-preserving, and effective masquerade attack detector. In this thesis, I present a machine learning-based technique using a set of novel features that aim to reveal user intent. I hypothesize that each individual user knows his or her own file system well enough to search in a limited, targeted, and unique fashion in order to find information germane to their current task. Masqueraders, on the other hand, are not likely to know the file system and layout of another user's desktop, and would likely search more extensively and broadly in a manner that is different from that of the victim user being impersonated. Based on this assumption, I model a user's search behavior and monitor deviations from it that could indicate fraudulent behavior. I identify user search events using a taxonomy of Windows applications, DLLs, and user commands. The taxonomy abstracts the user commands and actions and enriches them with contextual information. Experimental results show that modeling search behavior reliably detects all simulated masquerade activity with a very low false positive rate of 1.12%, far better than any previously published results. The limited set of features used for search behavior modeling also results in considerable performance gains over the same modeling techniques that use larger sets of features, both during sensor training and deployment. While an anomaly- or profiling-based detection approach, such as the one used in the user search profiling sensor, has the advantage of detecting unknown attacks and fraudulent masquerade behaviors, it suffers from a relatively high number of false positives and remains potentially vulnerable to mimicry attacks. To further improve the accuracy of the user search profiling approach, I supplement it with a trap-based detection approach. I monitor user actions directed at decoy documents embedded in the user's local file system. The decoy documents, which contain enticing information to the attacker, are known to the legitimate user of the system, and therefore should not be touched by him or her. Access to these decoy files, therefore, should highly suggest the presence of a masquerader. A decoy document access sensor detects any action that requires loading the decoy document into memory such as reading the document, copying it, or zipping it. I conducted human subject studies to investigate the deployment-related properties of decoy documents and to determine how decoys should be strategically deployed in a file system in order to maximize their masquerade detection ability. Our user study results show that effective deployment of decoys allows for the detection of all masquerade activity within ten minutes of its onset at most. I use the decoy access sensor as an oracle for the user search profiling sensor. If abnormal search behavior is detected, I hypothesize that suspicious activity is taking place and validate the hypothesis by checking for accesses to decoy documents. Combining the two sensors and detection techniques reduces the false positive rate to 0.77%, and hardens the sensor against mimicry attacks. The overall sensor has very limited resource requirements (40 KB) and does not introduce any noticeable delay to the user when performing its monitoring actions. Finally, I seek to expand the search behavior profiling technique to detect, not only malicious masqueraders, but any other system users. I propose a diversified and personalized user behavior profiling approach to improve the accuracy of user behavior models. The ultimate goal is to augment existing computer security features such as passwords with user behavior models, as behavior information is not readily available to be stolen and its use could substantially raise the bar for malefactors seeking to perpetrate masquerade attacks