We analyze optical binary communication assisted by entanglement and show that: i) ideal entangled channels have smaller error probability than ideal single-mode coherent channels if the photon number of the channel is larger than one; ii) realistic entangled channels with heterodyne receivers have smaller error probability than ideal single-mode coherent channels if the photon number of the ch...

We define a class of symmetric discrete memoryless multiple-access channels. This definition incorporates previous definitions of symmetry for single user channels and is characterized by the optimality of the uniform distribution with respect to total channel capacity. We further identify a sub-class of channels in which channel symmetry is a direct result of a transposition symmetry in the tr...

Attackers in particular botnet controllers use stealthy messaging systems to set up large-scale command and control. Understanding the capacity of such communication channels is important in detecting organized cyber crimes. We analyze the use of domain name service (DNS) as a stealthy botnet command-and-control channel, which allows multiple entities to pass messages stored in DNS records to e...

This paper considers steganography – the concept of hiding the presence of secret messages in legal communications – in the computational setting and its relation to cryptography. Very recently the first (non-polynomial time) steganographic protocol has been shown which, for any communication channel, is provably secure, reliable, and has nearly optimal bandwidth. The security is unconditional,...

It is a common practice to design a protocol (say Q) assuming some secure channels. Then the secure channels are implemented using any standard protocol, e.g. TLS. In this paper, we study when such a practice is indeed secure. We provide a characterization of both confidential and authenticated channels. As an application, we study several protocols of the literature including TLS and BAC proto...

This paper investigates the problem of communicating video over a broadcast channel. The broadcast channel is expressed in terms of the channel capacity that exists between the transmitter and each receiver in the broadcast area { Shannon's separation theorem does not apply for video communication over this class of channels. Digital (discrete time, discrete amplitude) and hybrid (discrete time...

We consider communication between two parties using a bipartite quantum operation, which constitutes the most general quantum mechanical model of two-party communication. We primarily focus on the simultaneous forward and backward communication of classical messages. For the case in which the two parties share unlimited prior entanglement, we give inner and outer bounds on the achievable rate r...