<p>Research in engineering design assumes that data flows smoothly among different designers within a product realization process. This assumption is not valid in many scenarios, including when designers partner with a future competitor or when designers search for potential collaborators is hampered by an inability to share sensitive data. This information asymmetry among designers has an adverse effect on the outcomes of the product realization process. Designers need a secure yet collaborative design process that enables them to overcome these information-related risks borne from collaborators participating in their product realization process. Existing cryptographic techniques aimed at overcoming these risks are computationally intensive, making them unsuitable for heavy engineering computations such as finite element analysis (FEA). FEA is a widely used computation technique in several engineering applications, including structural analysis, heat transfer, and fluid flow. In this work, we developed a new approach, secure finite element analysis (sFEA), using which designers can perform their analysis without revealing their confidential design data to anyone, including their design collaborators even though the computed answer depends on confidential inputs from all the collaborators. sFEA is a secure, scalable, computationally lightweight, and cloud-compatible. In addition to sFEA, we developed prototypes and demonstrated that the computational framework within sFEA is general enough to be applied to different stages of the product realization process.</p>

Many systems contain sensitive data such as user credentials used for authentication purposes. For large systems, a common approach is to store the data in a configuration file at a trusted third party. However, that would imply a single point of failure if an adversary gains access to the trusted party. In theory this could be solved by encrypting the data but in practice this only moves the problem and does not solve it, since some type of credential data is needed to decrypt the configuration file. A more flexible solution is needed that requires less of human interaction while also providing a higher degree of security. This thesis proposes a complete cryptographical system for solving this problem in a typical enterprise setting with a set of additional implementation requirements by using multi-party computation and Shamir's secret sharing protocol. Additionally, the work combines the mentioned system with a certificateless cryptography based multi-party computation protocol, since certificates usually implies a time-consuming process. The system has been evaluated in terms of security and efficiency with the conclusion that the results look promising. In terms of performance, the bulk of the overhead comes from certificateless cryptography, a constraint for the specific scenario which might not be present in general. The work also provides incentives for developing and further evolving Java libraries for cryptography, especially for multi-party computation and certificateless cryptography. / Många system innehåller känslig data, exempelvis användaruppgifter som används för autentiseringsändamål. För stora system är en vanlig lösning att lagra data i en konfigurationsfil hos en betrodd tredje part. Det skulle emellertid innebära att den svagaste länken är om motståndare får tillgång till den betrodda parten. I teorin kan detta lösas genom att kryptera data men i praktiken flyttar det bara på problemet men löser det inte, eftersom någon typ av autentiseringsdata behövs för att dekryptera konfigurationsfilen. En mer flexibel lösning behövs som kräver mindre mänsklig interaktion samtidigt som det ger en högre grad av säkerhet. Denna avhandling föreslår ett komplett kryptografiskt system för att lösa detta problem i en typisk företagsmiljö med en ytterligare uppsättning implementationskrav genom att använda multipartsberäknande och Shamirs secret sharing protokoll. Dessutom kombinerar arbetet det nämnda systemet med ett certifikatfritt krypteringsbaserat protokoll kombinerat med multipartsberäkningar, eftersom certifikat oftast innebär en tidskrävande process. Systemet har utvärderats med avseende på säkerhet och effektivitet med slutsatsen att det ser lovande ut. När det gäller prestanda kommer huvuddelen av omkostnaden från den certifikatfria kryptografin, en begränsning för det specifika scenariot som kanske inte är närvarande i allmänhet. Arbetet ger också motiv för att vidareutveckla Java-bibliotek för kryptografi, speciellt för multipartsberäknande protokoll och certifikatlös kryptering.

This work modifies Shamir’s algorithm by sharing a random key that is used to lock up the secret data; as against sharing the data itself. This is significant in cloud computing, especially with homomorphic encryption. Using web design, the resultant scheme practically globalises secret sharing with authentications and inherent secondary applications. The work aims at improving cybersecurity via a joint exploitation of human factors and technology; a human-centred cybersecurity design as opposed to technology-centred. The completed functional scheme is tagged CDRSAS. The literature on secret sharing schemes is reviewed together with the concepts of human factors, trust, cyberspace/cryptology and an analysis on a 3-factor security assessment process. This is followed by the relevance of passwords within the context of human factors. The main research design/implementation and system performance are analysed, together with a proposal for a new antidote against 419 fraudsters. Two twin equations were invented in the investigation process; a pair each for secret sharing and a risk-centred security assessment technique. The building blocks/software used for the CDRSAS include Shamir’s algorithm, MD5, HTML5, PHP, Java, Servlets, JSP, Javascript, MySQL, JQuery, CSS, MATLAB, MS Excel, MS Visio, and Photoshop. The codes are developed in Eclipse IDE, and the Java-based system runs on Tomcat and Apache, using XAMPP Server. Its code units have passed JUnit tests. The system compares favourably with SSSS. Defeating socio-cryptanalysis in cyberspace requires strategies that are centred on human trust, trust-related human attributes, and technology. The PhD research is completed but there is scope for future work. / Petroleum Technology Development Fund (PTDF), Abuja, Nigeria.

Secure multi-party computation (secure MPC) has been established as the de facto paradigm for protecting privacy in distributed computation. One of the earliest secure MPC primitives is the Shamir's secret sharing (SSS) scheme. SSS has many advantages over other popular secure MPC primitives like garbled circuits (GC) -- it provides information-theoretic security guarantee, requires no complex long-integer operations, and often leads to more efficient protocols. Nonetheless, SSS receives less attention in the signal processing community because SSS requires a larger number of honest participants, making it prone to collusion attacks. In this dissertation, I propose an agent-based computing framework using SSS to protect privacy in distributed signal processing. There are three main contributions to this dissertation. First, the proposed computing framework is shown to be significantly more efficient than GC. Second, a novel game-theoretical framework is proposed to analyze different types of collusion attacks. Third, using the proposed game-theoretical framework, specific mechanism designs are developed to deter collusion attacks in a fully distributed manner. Specifically, for a collusion attack with known detectors, I analyze it as games between secret owners and show that the attack can be effectively deterred by an explicit retaliation mechanism. For a general attack without detectors, I expand the scope of the game to include the computing agents and provide deterrence through deceptive collusion requests. The correctness and privacy of the protocols are proved under a covert adversarial model. Our experimental results demonstrate the efficiency of SSS-based protocols and the validity of our mechanism design.

Depuis la fin des années 90, les cryptosystèmes implantés sur carte à puce doivent faire face à deux grandes catégories d'attaques : les attaques par canaux cachés et les attaques par injection de fautes. Pour s'en prémunir, des contre-mesures sont élaborées, puis validées en considérant un modèle d'attaquant bien défini. Les travaux réalisés dans cette thèse se concentrent sur la protection des cryptosystèmes symétriques contre les attaques par canaux cachés. Plus précisément, on s'intéresse aux contre-mesures de masquage permettant de se prémunir des attaques statistiques d'ordre supérieur pour lesquelles un attaquant est capable de cibler t valeurs intermédiaires. Après avoir rappelé l'analogie entre les contre-mesures de masquage et les schémas de partage de secret, on présente la construction des schémas de partage de secret à partir de codes linéaires, introduite par James L. Massey en 1993. En adaptant cette construction et des outils issus du calcul multi-parties, on propose une méthode générique de contre-mesure de masquage résistante aux attaques statistiques d'ordre supérieur. De plus, en fonction des cryptosystèmes à protéger et donc des opérations à effectuer, cette solution permet d'optimiserle coût induit par les contre-mesures en sélectionnant les codes les plus adéquats. Dans cette optique, on propose deux contre-mesures de masquage pour implanter le cryptosystème AES. La première est basée sur une famille de code d'évaluation proche de celle utilisée pour le schéma de partage de secret de Shamir, tandis que la seconde considéré la famille des codes auto-duaux et faiblement auto-duaux ayant leur matrice génératrice à coefficient sur F2 ou F4. Ces deux alternatives se révèlent plus efficaces que les contremesures de masquage publiées en 2011 et basées sur le schéma de partage de secret de Shamir. De plus la seconde s'avère compétitive pour t=1 comparée aux solutions usuelles. / Since the late 90s, the implementation of cryptosystems on smart card faces two kinds of attacks : side-channel attacks and fault injection attacks. Countermeasures are then developed and validated by considering a well-defined attacker model. This thesis focuses on the protection of symmetric cryptosystems against side-channel attacks. Specifically, we are interested in masking countermeasures in order to tackle high-order attacks for which an attacker is capable of targeting t intermediate values. After recalling the analogy between masking countermeasures and secret sharing schemes, the construction of secret sharing schemes from linear codes introduced by James L. Massey in 1993 is presented.By adapting this construction together with tools from the field of Multi-Party Computation, we propose a generic masking countermeasure resistant to high-order attacks. Furthermore, depending on the cryptosystem to protect, this solution optimizes the cost of the countermeasure by selecting the most appropriate code. In this context, we propose two countermeasures to implement the AES cryptosystem. The first is based on a family of evaluation codes similar to the Reed Solomon code used in the secret sharing scheme of Shamir. The second considers the family of self-dual and self-orthogonal codes generated by a matrix defined over GF(2) or GF(4). These two alternatives are more effective than masking countermeasures from 2011 based on Shamir's secret sharing scheme. Moreover, for t=1, the second solution is competitive with usual solutions.

This work modifies Shamir’s algorithm by sharing a random key that is used to lock up the secret data; as against sharing the data itself. This is significant in cloud computing, especially with homomorphic encryption. Using web design, the resultant scheme practically globalises secret sharing with authentications and inherent secondary applications. The work aims at improving cybersecurity via a joint exploitation of human factors and technology; a human-centred cybersecurity design as opposed to technology-centred. The completed functional scheme is tagged CDRSAS. The literature on secret sharing schemes is reviewed together with the concepts of human factors, trust, cyberspace/cryptology and an analysis on a 3-factor security assessment process. This is followed by the relevance of passwords within the context of human factors. The main research design/implementation and system performance are analysed, together with a proposal for a new antidote against 419 fraudsters. Two twin equations were invented in the investigation process; a pair each for secret sharing and a risk-centred security assessment technique. The building blocks/software used for the CDRSAS include Shamir’s algorithm, MD5, HTML5, PHP, Java, Servlets, JSP, Javascript, MySQL, JQuery, CSS, MATLAB, MS Excel, MS Visio, and Photoshop. The codes are developed in Eclipse IDE, and the Java-based system runs on Tomcat and Apache, using XAMPP Server. Its code units have passed JUnit tests. The system compares favourably with SSSS. Defeating socio-cryptanalysis in cyberspace requires strategies that are centred on human trust, trust-related human attributes, and technology. The PhD research is completed but there is scope for future work.

Finnegan Lab System is a graphical computer program for learning how secret sharing works. With its focus on the algorithms and the data streams, the user does not have to consider machine-specific low-level details. It is highly modularised and is not restricted to secret sharing, but can easily be extended with new functions, such as building blocks for Feistel networks or signal processing. This thesis describes what secret sharing is, the development of a new lab system designed for secret sharing and how it can be used.

Using a Key escrow agent in conjunction with Voice over IP (VoIP) communication ensures that law enforcements agencies (LEAs) can retrieve the session key used to encrypt data between two users in a VoIP session. However, the use of a single escrow agent has some drawbacks. A fraudulent request by an evil employee from the LEA can lead to improper disclosure of a session key. After the escrow agent reveals the key this evil person could fabricate data according to his/her needs and encrypt it again (using the correct session key). In this situation the persons involved in the communication session can be accused of crimes that he or she or they never committed. The problems with a single escrow agent becomes even more critical as a failure of the escrow agent can delay or even make it impossible to reveal the session key, thus the escrow agent might not be able to comply with a lawful court order or comply with their escrow agreement in the case of data being released according to this agreement (for example for disaster recovery). This thesis project focused on improving the accessibility and reliability of escrow agents, while providing good security. One such method is based on dividing the session key into M chunks and escrowing the chunks with M escrow agents. Using threshold cryptography the key can be regenerated by gathering any N-out-of-M chunks. The value of M and N may differ according to the role of the user. For a highly sophisticated session, the user might define a higher value for M and N for improved, availability, reliability, and security. For a less confidential or less important session (call), the value of M and N might be smaller. The thesis examines the increased availability and increased reliability made possible by using multiple escrow agents. / Med en nyckel förvaringsinstitut som tillsammans med Röst över IP (VoIP) kommunikation säkerställer att brottsbekämpande organ (LEAs) kan hämta sessionsnyckeln används för att kryptera data mellan två användare i en VoIP-session. Däremot har användningen av ett enda förvaringsinstitut visa nackdelar. En bedräglig begäran av en ond arbetstagare från LEA kan leda till otillbörligt röjande av en sessionsnyckel. Efter förvaringsinstitut avslöjar nyckeln detta onda person kunde fabricera uppgifter i enlighet med hans eller hennes behov och kryptera den igen (med rätt sessionsnyckel). I denna situation personer som deltar i kommunikationssession kan anklagas för brott som han eller hon eller de aldrig begått. Problemen med en enda förvaringsinstitut som blir ännu mer kritisk som ett misslyckande av förvaringsinstitut kan försena eller till och med gör det omöjligt att avslöja sessionsnyckeln, vilket förvaringsinstituten kanske inte kan följa en laglig domstolsbeslut eller uppfyller sina depositionsavtalets när det gäller data frisläppas i enlighet med detta avtal (till exempel för katastrofer). Detta examensarbete fokuserar på att förbättra tillgängligheten och tillförlitligheten i spärrade medel, samtidigt som god säkerhet. En sådan metod bygger på att dela upp sessionsnyckeln till M bitar och escrowing i bitar med M förvaringsinstituten. Använda tröskel kryptografi nyckeln kan genereras genom att samla alla N-out-of-M bitar. Värdet på M och N kan variera beroende på användarens roll. För en mycket sofistikerad session kan användaren definiera ett högre värde för M och N för förbättrad tillgänglighet, tillförlitlighet och säkerhet. För en mindre konfidentiell eller mindre viktigt session (telefonsamtal), kan värdet på M och N vara mindre. I avhandlingen analyseras den ökade tillgänglighet och ökad tillförlitlighet möjligt genom att använda flera spärrade medel.

Storing personal information in a secure and reliable manner may be crucial for organizational as well as private users. Encryption protects the confidentiality of data against adversaries but if the cryptographic key is lost, the information will not be obtainable for authorized individuals either. Redundancy may protect information against availability issues or data loss, but also comes with greater storage overhead and cost. Cloud storage serves as an attractive alternative to traditional storage as one is released from maintenance responsibilities and does not have to invest in in-house IT-resources. However, cloud adoption is commonly hindered due to privacy concerns. Instead of relying on the security of a single cloud, this study aims to investigate the applicability of a multi-cloud solution based on Secret Sharing, and to identify suitable options and guidelines in a configuration user interface (UI). Interviews were conducted with technically skilled people representing prospective users, followed by walkthroughs of a UI prototype. Although the solution would (theoretically) allow for employment of less “trustworthy” clouds without compromising the data confidentiality, the research results indicate that trust factors such as compliance with EU laws may still be a crucial prerequisite in order for users to utilize cloud services. Users may worry about cloud storage providers colluding, and the solution may not be perceived as adequately secure without the use of encryption. The configuration of the Secret Sharing parameters are difficult to comprehend even for technically skilled individuals and default values could/should be recommended to the user. / PRISMACLOUD

Many e-voting techniques have been proposed but not widely used in reality. One of the problems associated with most of existing e-voting techniques is the lack of transparency, leading to a failure to deliver voter assurance. In this work, we propose a transparent, auditable, end-to-end verifiable, and mutual restraining e-voting protocol that exploits the existing multi-party political dynamics such as in the US. The new e-voting protocol consists of three original technical contributions -- universal verifiable voting vector, forward and backward mutual lock voting, and in-process check and enforcement -- that, along with a public real time bulletin board, resolves the apparent conflicts in voting such as anonymity vs. accountability and privacy vs. verifiability. Especially, the trust is split equally among tallying authorities who have conflicting interests and will technically restrain each other. The voting and tallying processes are transparent to voters and any third party, which allow any voter to verify that his vote is indeed counted and also allow any third party to audit the tally. For the environment requiring receipt-freeness and coercion-resistance, we introduce additional approaches to counter vote-selling and voter-coercion issues. Our interactive voting protocol is suitable for small number of voters like boardroom voting where interaction between voters is encouraged and self-tallying is necessary; while our non-interactive protocol is for the scenario of large number of voters where interaction is prohibitively expensive. Equipped with a hierarchical voting structure, our protocols can enable open and fair elections at any scale.