3 research outputs found
Byzantine Modification Detection in Multicast Networks With Random Network Coding
An information-theoretic approach for detecting Byzantine or adversarial modifications in networks employing random linear network coding is described. Each exogenous source packet is augmented with a flexible number of hash symbols that are obtained as a polynomial function of the data symbols. This approach depends only on the adversary not knowing the random coding coefficients of all other packets received by the sink nodes when designing its adversarial packets. We show how the detection probability varies with the overhead (ratio of hash to data symbols), coding field size, and the amount of information unknown to the adversary about the random code
Secure message transmission in the general adversary model
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 diff�erent measures of security: perfect (PSMT) and
almost perfect (APSMT). Moreover, reliable (but not private) message transmission (RMT) are considered as a specifi�c part of SMT. In this thesis, we study RMT, APSMT
and PSMT in two di�fferent 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 de�fine 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 di�fferent 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 signifi�cantly 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 di�fferent 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