On the Commitment Capacity of Unfair Noisy Channels. Noisy channels are a valuable resource from a cryptographic point of view. They can be used for exchanging secretkeys as well as realizing other cryptographic primitives such as commitment and oblivious transfer. To be really useful, noisy channels have to be consider in the scenario where a cheating party has some degree of control over the channel characteristics. Damgard et al. (EUROCRYPT 1999) proposed a more realistic model where such level of control is permitted to an adversary, the so called unfair noisy channels, and proved that they can be used to obtain commitment and oblivious transfer protocols. Given that noisy channels are a precious resource for cryptographic purposes, one important question is determining the optimal rate in which they can be used. The commitment capacity has already been determined for the cases of discrete memoryless channels and Gaussian channels. In this work we address the problem of determining the commitment capacity of unfair noisy channels. We compute a singleletter characterization of the commitment capacity of unfair noisy channels. In the case where an adversary has no control over the channel (the fair case) our capacity reduces to the wellknown capacity of a discrete memoryless binary symmetric channel.

On Secure Capacity of Multiple Unicast Traffic over Separable Networks This paper studies the problem of information theoretic secure communication when a source has private messages to transmit to m destinations, in the presence of a passive adversary who eavesdrops an unknown set of k edges. The information theoretic secure capacity is derived over unitedge capacity separable networks, for the cases when k  1 and m is arbitrary, or m  3 and k is arbitrary. This is achieved by first showing that there exists a secure polynomialtime code construction that matches an outer bound over twolayer networks, followed by a deterministic mapping between twolayer and arbitrary separable networks.