Keeping sensitive information private in a public world is a common concern to users of digital credentials. A digital credential may contain sensitive attributes certifying characteristics about its owner. X.509v3, the most widely used certificate standard, includes support for certificate extensions that make it possible to bind multiple attributes to a public key contained in the certificate. This feature, although convenient, potentially exploits the certificate holder's private information contained in the certificate. There are currently no privacy considerations in place to protect the disclosure of attributes in a certificate. This thesis focuses on protecting sensitive credential content during trust negotiation and demonstrates, through design and implementation, the privacy benefits achieved through selective disclosure. Selective disclosure of credential content can be achieved using private attributes, a well-known technique that incorporates bit commitment within digital credentials. This technique has not been thoroughly explored or implemented in any prior work. In this thesis, a protocol for issuing and showing credentials containing private attributes is discussed and suggested as a method for concealing and selectively revealing sensitive attributes bound to credentials during trust negotiation. To demonstrate greater privacy control within a credential-based system, private attributes are incorporated into TrustBuilder, an implementation of trust negotiation. With access control at the attribute level, TrustBuilder gives users greater control over their private information and can improve the success rate of negotiations. TrustBuilder also demonstrates how credentials with private attributes can eliminate risks normally associated with exchanging credentials, such as excessive gathering of information that is not germane to the transaction and inadvertently disclosing the value of a sensitive credential attribute.

This thesis proposes an Ecosystem perspective for the engineering of SoS and CPS and illustrates the impact of this perspective in three areas of contribution category First, from a conceptual and Systems Engineering perspective, a conceptual framework including the Ecosystems of System Unified Language Modeling (EoS-UML) profile, a set of Ecosystem Ensemble Diagrams, the Arms :Length Trust Model and the Cyber Physical Threat Model are provided. Second, having established this conceptual view of the ecosystem, we recognize unique role of the cryptographic credentials within it, towards enabling the ecosystem long-term value proposition and acting as a value transfer agent, implementing careful balance of properties meet stakeholder needs. Third, we propose that the ecosystem computers can be used as a distributed compute engine to run Collaborative Algorithms. To demonstrate, we define access control scheme, risk-balanced Cellular Access Control (rbCAC). The rbCAC algorithm defines access control within a cyber-physical environment in a manner which balances cost, risk, and net utility in a multi-authority setting. rbCAC is demonstrated it in an Air Travel and Border Services scenario. Other domains are also discussed included air traffic control threat prevention from drone identity attacks in protected airspaces. These contributions offer significant material for future development, ongoing credential and ecosystem design, including dynamic perimeters and continuous-time sampling, intelligent and self optimizing ecosystems, runtime collaborative platform design contracts and constraints, and analysis of APT attacks to SCADA systems using ecosystem approaches.