<p>This thesis describes the system design and implementation of the secure Ephemerizer System that was first introduced by Radia Perlman in 2005. The system is designed to enable users to keep data for a finite period of time before making the data unrecoverable by destroying the keys with which the data was encrypted. The task of the Ephemerizer System service is to create, advertise, and destroy keys required for the Ephemerizer System's functionalities.</p><p>We designed the Ephemerizer System Service's security by placing the sensitive key management modules into a Trusted Computing Base (TCB). Our compartmentalized approach distributes security requirements at different sensitivity levels into different protection domains. In our approach, we implement the trusted protection domain (our TCB) on a tamper-resistant Javacard.</p><p>We placed the key storage database into the partly trusted protection domain to improve scalability and availability of the Ephemerizer System. The partly trusted protection domain requires memory isolation and other security mechanisms provided by the underlying operating system. We implemented several mechanisms on the TCB, such as the signature engine, cryptographic modules, the on-card expiration validator, and on-card time verification. We make the Ephemerizer System available to users as a web service and expose it though a uniform API. This approach enables the seamless integration of the Ephemerizer System into business processes on heterogeneous platforms.</p>

Desktop and mobile computing devices increasingly store critical data, both personal and professional in nature. Yet, the enormous code bases of their monolithic operating systems (hundreds of thousands to millions of lines of code) are likely to contain exploitable weaknesses that jeopardize the security of this data in the file system. Using a highly componentized system architecture based on a microkernel (or a very small hypervisor) can significantly improve security. The individual operating system components have smaller code bases running in isolated address spaces so as to provide better fault containment. Their isolation also allows for smaller trusted computing bases (TCBs) of applications that comprise only a subset of all components. In my thesis, I built VPFS, a virtual private file system that is designed for such a componentized system architecture. It aims at reducing the amount of code and complexity that a file system implementation adds to the TCB of an application. The basic idea behind VPFS is similar to that of a VPN, which securely reuses an untrusted network: The core component of VPFS implements all functionality and cryptographic algorithms that an application needs to rely upon for confidentiality and integrity of file system contents. These security-critical cores reuse a much more complex and therefore untrusted file system stack for non-critical functionality and access to the storage device. Additional trusted components ensure recoverability.

Desktop and mobile computing devices increasingly store critical data, both personal and professional in nature. Yet, the enormous code bases of their monolithic operating systems (hundreds of thousands to millions of lines of code) are likely to contain exploitable weaknesses that jeopardize the security of this data in the file system. Using a highly componentized system architecture based on a microkernel (or a very small hypervisor) can significantly improve security. The individual operating system components have smaller code bases running in isolated address spaces so as to provide better fault containment. Their isolation also allows for smaller trusted computing bases (TCBs) of applications that comprise only a subset of all components. In my thesis, I built VPFS, a virtual private file system that is designed for such a componentized system architecture. It aims at reducing the amount of code and complexity that a file system implementation adds to the TCB of an application. The basic idea behind VPFS is similar to that of a VPN, which securely reuses an untrusted network: The core component of VPFS implements all functionality and cryptographic algorithms that an application needs to rely upon for confidentiality and integrity of file system contents. These security-critical cores reuse a much more complex and therefore untrusted file system stack for non-critical functionality and access to the storage device. Additional trusted components ensure recoverability.

The OS (operating system) is the primary target of todays attacks. A single exploitable defect can be sufficient to break the security of the system and give fully control over all the software on the machine. Because current operating systems are too large to be defect free, the best approach to improve the system security is to reduce their code to more manageable levels. This work shows how the security-critical part of the OS, the so called TCB (Trusted Computing Base), can be reduced from millions to less than hundred thousand lines of code to achieve these security goals. Shrinking the software stack by more than an order of magnitude is an open challenge since no single technique can currently achieve this. We therefore followed a holistic approach and improved the design as well as implementation of several system layers starting with a new OS called NOVA. NOVA provides a small TCB for both newly written applications but also for legacy code running inside virtual machines. Virtualization is thereby the key technique to ensure that compatibility requirements will not increase the minimal TCB of our system. The main contribution of this work is to show how the virtual machine monitor for NOVA was implemented with significantly less lines of code without affecting the performance of its guest OS. To reduce the overall TCB of our system, other parts had to be improved as well. Additional contributions are the simplification of the OS debugging interface, the reduction of the boot stack and a new programming language called B1 that can be more easily compiled.

This thesis describes the system design and implementation of the secure Ephemerizer System that was first introduced by Radia Perlman in 2005. The system is designed to enable users to keep data for a finite period of time before making the data unrecoverable by destroying the keys with which the data was encrypted. The task of the Ephemerizer System service is to create, advertise, and destroy keys required for the Ephemerizer System's functionalities. We designed the Ephemerizer System Service's security by placing the sensitive key management modules into a Trusted Computing Base (TCB). Our compartmentalized approach distributes security requirements at different sensitivity levels into different protection domains. In our approach, we implement the trusted protection domain (our TCB) on a tamper-resistant Javacard. We placed the key storage database into the partly trusted protection domain to improve scalability and availability of the Ephemerizer System. The partly trusted protection domain requires memory isolation and other security mechanisms provided by the underlying operating system. We implemented several mechanisms on the TCB, such as the signature engine, cryptographic modules, the on-card expiration validator, and on-card time verification. We make the Ephemerizer System available to users as a web service and expose it though a uniform API. This approach enables the seamless integration of the Ephemerizer System into business processes on heterogeneous platforms.

Critical infrastructures like oil & gas, power grids, water treatment facilities, domain name system (DNS) etc., are attractive targets for attackers — both due to the potential impact of attacks on such systems, and due to the enormous attack surface exposed by such systems. Unwarranted functionality in the form of accidental bugs or maliciously inserted hidden functionality in any component of a system could potentially be exploited by attackers to launch attacks on the system. As it is far from practical to root out undesired functionality in every component of a complex system, it is essential to develop security measures for protecting CI systems that rely only on the integrity of a small number of carefully constructed components, identified as the trusted computing base (TCB) for the system. The broad aim of this dissertation is to characterize elements of the TCB for critical infrastructure systems, and outline strategies to leverage the TCB to secure CI systems. A unified provider-middleman-consumer (PMC) view of systems was adopted to characterize systems as being constituted by providers of data, untrusted middlemen, and consumers of data. As the goal of proposed approach is to eliminate the need to trust most components of a system to be secured, most components of the system are considered to fall under the category of “untrusted middlemen.” From this perspective, the TCB for the system is a minimal set of trusted functionality required to verify that the tasks performed by the middle-men will not result in violation of the desired assurances. Specific systems that were investigated in this dissertation work to characterize the minimal TCB included the domain name system (DNS), dynamic DNS, and Supervisory Control and Data Acquisition (SCADA) systems that monitor/control various CI systems. For such systems, this dissertation provides a comprehensive functional specification of the TCB, and outlines security protocols that leverage the trust in TCB functionality to realize the desired assurances regarding the system.

No description available.

The OS (operating system) is the primary target of todays attacks. A single exploitable defect can be sufficient to break the security of the system and give fully control over all the software on the machine. Because current operating systems are too large to be defect free, the best approach to improve the system security is to reduce their code to more manageable levels. This work shows how the security-critical part of the OS, the so called TCB (Trusted Computing Base), can be reduced from millions to less than hundred thousand lines of code to achieve these security goals. Shrinking the software stack by more than an order of magnitude is an open challenge since no single technique can currently achieve this. We therefore followed a holistic approach and improved the design as well as implementation of several system layers starting with a new OS called NOVA. NOVA provides a small TCB for both newly written applications but also for legacy code running inside virtual machines. Virtualization is thereby the key technique to ensure that compatibility requirements will not increase the minimal TCB of our system. The main contribution of this work is to show how the virtual machine monitor for NOVA was implemented with significantly less lines of code without affecting the performance of its guest OS. To reduce the overall TCB of our system, other parts had to be improved as well. Additional contributions are the simplification of the OS debugging interface, the reduction of the boot stack and a new programming language called B1 that can be more easily compiled.

The integrity of information systems is predicated on the integrity of processes that manipulate data. Processes are conventionally executed using the conventional von Neumann (VN) architecture. The VN computation model is plagued by a large trusted computing base (TCB), due to the need to include memory and input/output devices inside the TCB. This situation is becoming increasingly unjustifiable due to the steady addition of complex features such as platform virtualization, hyper-threading, etc. In this research work, we propose a new model of computation - TCB minimizing model of computation (TMMC) - which explicitly seeks to minimize the TCB, viz., hardware and software that need to be trusted to guarantee the integrity of execution of a process. More specifically, in one realization of the model, the TCB can be shrunk to include only a low complexity module; in a second realization, the TCB can be shrunk to include nothing, by executing processes in a blockchain network. The practical utilization of TMMC using a low complexity trusted module, as well as a blockchain network, is detailed in this research work. The utility of the TMMC model in guaranteeing the integrity of execution of a wide range of useful algorithms (graph algorithms, computational geometric algorithms, NP algorithms, etc.), and complex large-scale processes composed of such algorithms, are investigated.

Trust in information systems stem from two key properties of responses to queries regarding the state of the system, viz., i) authoritativeness, and ii) unbiasedness. That the response is authoritative implies that i) the provider (source) of the response, and ii) the chain of delegations through which the provider obtained the authority to respond, can be verified. The property of unbiasedness implies that no system data relevant to the query is deliberately or accidentally suppressed. The need for guaranteeing these two important properties stem from the impracticality for the verifier to exhaustively verify the correctness of every system process, and the integrity of the platform on which system processes are executed. For instance, the integrity of a process may be jeopardized by i) bugs (attacks) in computing hardware like Random Access Memory (RAM), input/output channels (I/O), and Central Processing Unit( CPU), ii) exploitable defects in an operating system, iii) logical bugs in program implementation, and iv) a wide range of other embedded malfunctions, among others. A first step in ensuing AU properties of geographic queries is the need to ensure AU responses to a specific type of geographic query, viz., point-location. The focus of this dissertation is on strategies to leverage assured point-location, for i) ensuring authoritativeness and unbiasedness (AU) of responses to a wide range of geographic queries; and ii) useful applications like Secure Queryable Dynamic Maps (SQDM) and trustworthy redistricting protocol. The specific strategies used for guaranteeing AU properties of geographic services include i) use of novel Merkle-hash tree- based data structures, and ii) blockchain networks to guarantee the integrity of the processes.