New results on secure message transmission
Reihaneh Safavi–Naini, Mohammed Ashraful Alam Tuhin
In the Secure Message Transmission (SMT) problem two nodes in a network want to communicate securely (both privately and reliably), given that some of the nodes in the network are corrupted by an adaptive byzantine adversary with unlimited computational power. A SMT protocol uses multiple paths between the sender S and a receiver R to guarantee privacy and reliability of the message transmission. Privacy means that the adversary learns no information about the transmitted secret, whereas reliability means that the receiver always receives the message sent by the sender. S and R are connected by n disjoint paths where a subset of which (at most t in case of a threshold adversary) can be corrupted by an adversary. Efficiency parameters of a SMT protocol are the number of rounds (number of interactions between S and R ), communication complexity, and computational complexity. An (e, δ)-SMT protocol bounds the adversary's success probability of breaking privacy and reliability to e and δ, respectively. A SMT protocol for a given number of rounds is optimal if its transmission rate (amount of communication per one bit of message) matches the lower bound for that number of rounds. Optimal protocols have been constructed for a restricted set of parameters. It has been proved that secure SMT is possible if and only if n ≥ 2t + 1, where t is the number of paths corrupted by the adversary.
This thesis describes a number of contributions to the study of SMT problem. First, we improve the system parameter of a previously introduced wire virtualization method for constructing optimal protocols using two component protocols. Using the improved wire virtualization method we present the first optimal 1-round (0, δ)-SMT protocol for higher connectivity.
Then we introduce a modular approach for constructing SMT protocols using two or more modules. Using this approach we design an optimal 1-round (0, δ)-SMT protocol for the minimum connectivity, which has higher reliability than any comparable protocol. We also design a similar protocol for higher connectivity improving the reliability of the protocol presented in the first part of this thesis.
Constructing secure and efficient (in communication) SMT protocols against a threshold adversary has been extensively researched. However less is known about SMT problem for a generalized adversary who can corrupt one out of a set of possible subsets. In this part of the thesis, we focus on 1-round (0, δ)-SMT protocols against a generalized adversary. These protocols are especially attractive because of their possible practical applications.
Finally, we introduce a new security definition by presenting an alternative privacy definition, which is based on guessing advantage of the adversary, to construct more efficient (in communication) protocols. Our motivation is that if the received message is long enough and has sufficient entropy, then it can be used as a secret key. We give the relationship between the new security definition and the known one, and revisit bounds on connectivity and transmission rates of SMT protocols under the new definition. We also give constructions for a 1-round and a 3-round protocol, secure under the new definition, that are optimal.
The contributions made in this thesis add to the research on the secure message transmission problem and show new directions for future research.
•Jan 1, 2012•0 citations