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Title: Secure message transmission in the general adversary model
Author: Yang, Q.
ISNI:       0000 0004 2731 5934
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2011
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The problem of secure message transmission (SMT), due to its importance in both practice and theory, has been studied extensively. Given a communication network in which a sender S and a receiver R are indirectly connected by unreliable and distrusted channels, the aim of SMT is to enable messages to be transmitted from S to R with a reasonably high level of privacy and reliability. SMT must be achieved in the presence of a Byzantine adversary who has unlimited computational power and can corrupt the transmission. In the general adversary model, the adversary is characterized by an adversary structure. We study two different measures of security: perfect (PSMT) and almost perfect (APSMT). Moreover, reliable (but not private) message transmission (RMT) are considered as a specific part of SMT. In this thesis, we study RMT, APSMT and PSMT in two different network settings: point-to-point and multicast. To prepare the study of SMT in these two network settings, we present some ideas and observations on secret sharing schemes (SSSs), generalized linear codes and critical paths. First, we prove that the error-correcting capability of an almost perfect SSS is the same as a perfect SSS. Next, we regard general access structures as linear codes, and introduce some new properties that allow us to construct pseudo-basis for efficient PSMT protocol design. In addition, we define adversary structures over "critical paths", and observe their properties. Having these new developments, the contributions on SMT in the aforementioned two network settings can be presented as follows. The results on SMT in point-to-point networks are obtained in three aspects. First, we show a Guessing Attack on some existing PSMT protocols. This attack is critically important to the design of PSMT protocols in asymmetric networks. Second, we determine necessary and sufficient conditions for different levels of RMT and APSMT. In particular, by applying the result on almost perfect SSS, we show that relaxing the requirement of privacy does not weaken the minimal network connectivity. Our final contribution in the point-to-point model is to give the first ever efficient, constant round PSMT protocols in the general adversary model. These protocols are designed using linear codes and critical paths, and they significantly improve some previous results in terms of communication complexity and round complexity. Regarding SMT in multicast networks, we solve a problem that has been open for over a decade. That is, we show the necessary and sufficient conditions for all levels of SMT in different adversary models. First, we give an Extended Characterization of the network graphs based on our observation on the eavesdropping and separating activities of the adversary. Next, we determine the necessary and sufficient conditions for SMT in the general adversary model with the new Extended Characterization. Finally, we apply the results to the threshold adversary model to completely solve the problem of SMT in general multicast network graphs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available