The maximum likelihood attack strategy is known to be the optimal attack strategy for an eavesdropper in a wiretap channel scenario with additive white Gaussian noise channels under the distinguishing security criterion. The main drawback of this optimal attack is its high computational complexity. While this complexity doesn’t hinder the eavesdropper since he has unlimited computing power, it does present a significant challenge for legitimate parties. For them, it is extremely difficult, if not impossible, to estimate the outcome of the optimal attacker strategy to validate the secrecy of their communication system. In this paper, we introduce a low complexity method for generating upper and lower bounds on the attack performance of the eavesdropper to validate the security against the maximum likelihood attack strategy. We theoretically establish that the derived bounds represent valid constraints on the attack success probability under suitable constraints. The validation method is based on list generation and can be used for any linear block code. Furthermore, we propose a list generation algorithm for this validation method and show different ways to further reduce the complexity. We compare the proposed validation method with state-of-the-art attack strategies in numerical simulations for various error-correcting codes.

In this study, we examine different functions for the security layer of a seeded modular coding scheme for semantic security. We investigated the separation of the seed set into dispersing and non-dispersing seeds. The separation exists for all five implemented security functions in combination with all three tested error correcting codes. We show a simple procedure to reduce the probability of dispersing seeds for all security functions in two of three error correcting codes. Additionally, it was shown that Eve has an advantage in extracting information from her channel output if dispersing seeds are used. The simulations showed that this advantage can lead in special cases to a better information extraction despite larger encoding randomness. To the best of the authors’ knowledge, this is the first analytic comparison of different security functions for a seeded modular coding scheme of this kind.

We study the problem of common randomness (CR) generation in a fundamental two-party communication scenario, where a sender and a receiver seek to agree-with high probability-on a shared random variable. Both parties observe independent and identically distributed (i.i.d.) samples from sources defined over a Polish alphabet with an arbitrary joint distribution. Communication is restricted to a unidirectional, minimally interactive exchange over a noisy, memoryless channel. For this setting, we establish single-letter lower and upper bounds on the CR capacity. These bounds coincide except possibly at a countable set of points where discontinuities may arise.

This paper presents a novel approach to enhance sensing capabilities in UAV-enabled MIMO-OFDM ISAC systems by leveraging UAV mobility as a mono-static radar. By integrating uniform planar arrays (UPAs) and modeling the UAV dynamics in$S E(3)$, we address key challenges such as 3D space sensing and trajectory design. We propose a target tracking scheme using extended Kalman filtering (EKF) in$S E(3)$, along with trajectory optimization based on the conditional Posterior Cramer-Rao bound (CPCRB). Numerical results demonstrate the effectiveness of the proposed trajectory design in enhancing performance of target tracking and physical parameter estimation in UAVenabled MIMO-OFDM ISAC systems.

We investigate the problem of generating common randomness (CR) from a finite compound source aided by unidirectional communication over a rate-limited perfect channel. The two communicating parties observe independent and identically distributed (i.i.d.) samples of a finite compound source and aim to agree on a common random variable with high probability for every possible state. Both parties know the set of source states as well as their statistics. However, they don’t know the actual state. We establish a single-letter formula for the compound CR capacity in the presence of communication over the channel and study key properties of the compound CR capacity: superadditivity, concavity, and continuity. We also consider the case where there is no communication between the terminals, and only the source outputs observed by the terminal at the receiving end of the perfect channel are state-dependent. In this setting, we establish single-letter bounds on the compound CR capacity. The single-letter lower bound is derived under the assumption that the source distributions are pairwise distinct for all states. Finally, within the same setting, we propose a CR generation scheme for a two-state binary source example. Notably, this scheme does not depend on the previously mentioned assumption.

We investigate the problem of generating common randomness (CR) from finite compound sources aided by unidirectional communication over rate-limited perfect channels. The two communicating parties, often referred to as terminals, observe independent and identically distributed (i.i.d.) samples of a finite compound source and aim to agree on a common random variable with a high probability for every possible realization of the source state. Both parties know the set of source states as well as their statistics. However, they are unaware of the actual realization of the source state. We establish a single-letter lower and upper bound on the compound CR capacity for the specified model. Furthermore, we present two special scenarios where the established bounds coincide.

Abstract We introduce, motivate and study $$\varepsilon $$ ε -almost collision-flat universal (ACFU) hash functions $$f:\mathcal X\times \mathcal S\rightarrow \mathcal A$$ f : X × S → A . Their main property is that the number of collisions in any given value is bounded. Each $$\varepsilon $$ ε -ACFU hash function is an $$\varepsilon $$ ε -almost universal (AU) hash function, and every $$\varepsilon $$ ε -almost strongly universal (ASU) hash function is an $$\varepsilon $$ ε -ACFU hash function. We study how the size of the seed set $$\mathcal S$$ S depends on $$\varepsilon ,|\mathcal X |$$ ε , | X | and $$|\mathcal A |$$ | A | . Depending on how these parameters are interrelated, seed-minimizing ACFU hash functions are equivalent to mosaics of balanced incomplete block designs (BIBDs) or to duals of mosaics of quasi-symmetric block designs; in a third case, mosaics of transversal designs and nets yield seed-optimal ACFU hash functions, but a full characterization is missing. By either extending $$\mathcal S$$ S or $$\mathcal X$$ X , it is possible to obtain an $$\varepsilon $$ ε -ACFU hash function from an $$\varepsilon $$ ε -AU hash function or an $$\varepsilon $$ ε -ASU hash function, generalizing the construction of mosaics of designs from a given resolvable design (Gnilke et al. in Des. Codes Cryptogr. 86(1):85–95, 2017). The concatenation of an ASU and an ACFU hash function again yields an ACFU hash function. Finally, we motivate ACFU hash functions by their applicability in privacy amplification.

We investigate the problem of message transmission and the problem of common randomness (CR) generation over single-user multiple-input multiple-output (MIMO) slow fading channels with average input power constraint, additive white Gaussian noise (AWGN), arbitrary state distribution and with complete channel state information available at the receiver side (CSIR). We derive a lower and an upper bound on the outage transmission capacity of MIMO slow fading channels for arbitrary state distribution and show that the bounds coincide except possibly at points of discontinuity of the outage transmission capacity, of which there are, at most, countably many. Such discontinuity issues might occur because the channel state distribution is arbitrary. We also establish the capacity of a specific compound MIMO Gaussian channel in order to prove the lower bound on the outage transmission capacity. Furthermore, we define the outage CR capacity for a two-source model with unidirectional communication over a MIMO slow fading channel with arbitrary state distribution and establish a lower and an upper bound on it using our bounds on the outage transmission capacity of the MIMO slow fading channel.

This paper proposes a system architecture that embeds semantically-secure information-theoretic physical layer security (IT-PLS) non-intrusively into a 5G New Radio (NR) system in order to protect uplink transmissions via physical uplink control channels (PUCCH) against post-quantum eaves-dropping attacks. We implement a proof of concept of such system employing a code construction based on a modular coding scheme with a universal hash function that ensures semantic secrecy. We conduct link-level simulations of wiretap channels under different frequency-selective fading conditions and noise characteristics in order to evaluate the performance of such implementation for slow and fast fading scenarios. We model them using tapped delay line channel models involving rural and urban scenarios with line-of-sight (LOS) and non-LOS radio conditions, as specified by the 3GPP TR 38.901. We characterize such system by measuring the distinguishing error rate, block error rate, and secrecy outage probability under different time-varying fading channels. Our case study outlines how IT-PLS can be transparently embedded into future 6G systems as well.

This paper compares different algorithms to check semantic security on AWGN wiretap channels. Each algorithm provides upper and lower bounds on the performance of an attack strategy that is close to the best attack strategy. The advantage of these algorithms is that they have lower computational complexity compared to the best attack strategy. We also show that the proposed algorithms can be further improved by including cyclic redundancy check bits and parity check bits generated in the algorithms, for example, when polar codes or LDPC codes according to the 5G standard are used in the coding layer. Finally, we show the compatibility of the algorithms for both polar codes and LDPC codes.

We study a two-source model for common randomness (CR) generation in which the sender Alice and the receiver Bob generate a common random variable with a high probability of agreement by observing independent and identically distributed (i.i.d.) samples of correlated sources on countably infinite alphabets. The two parties are additionally allowed to communicate over a noisy memoryless channel. In our work, we establish a single-letter lower and upper-bound on the CR capacity for the proposed model. This is a challenging scenario because some of the finite alphabet properties, namely of the entropy can not be extended to the countably infinite case. We use a generalized typicality criterion, called unified typicality, which can be applied to random variables on countably infinite alphabets.

We consider a standard two-source model for uniform common randomness (UCR) generation, in which Alice and Bob observe independent and identically distributed (i. i. d.) samples of a correlated finite source and where Alice is allowed to send information to Bob over an arbitrary single-user channel. We study the ϵ-UCR capacity for the proposed model, defined as the maximum common randomness rate one can achieve such that the probability that Alice and Bob do not agree on a common uniform or nearly uniform random variable does not exceed ϵ. We establish a lower and an upper bound on the ϵ-UCR capacity using the bounds on the ϵ-transmission capacity proved by Verdú and Han for arbitrary point-to-point channels.A detailed version with all proofs, explanations and more discussions can be found in [1].

ε-Almost Collision-Flat Universal (ACFU) hash functions are defined and analyzed. They are motivated by their use in achieving information-theoretic key indistinguishability in privacy amplification. Lower bounds for the size of the seed set are given. A general method is presented by which to construct an ε-ACFU hash function from any ε-almost universal hash function. Several examples are studied. In particular, it turns out that all security functions known so far which achieve key indistinguishability universally are ε-ACFU hash functions.

In this paper we show a way to check semantic security for AWGN wiretap channels. We introduce low complexity decoding methods that provide upper and lower bounds to the performance of an attack strategy that closely resembles the best attack strategy, which has the problem of large computational complexity. We show the assumptions under which these methods can be applied and compare simulation results of the bounds to the performance of the best attack strategy. We use a seeded modular coding scheme, which consists of a coding layer and a security layer. For the coding layer we use polar codes, but the method is neither restricted to the seeded modular coding scheme nor to the polar codes.

Over the past decades, the problem of communication over finite-state Markov channels (FSMCs) has been investigated in many works and the capacity of FSMCs has been studied in closed form under the assumption of the availability of partial/complete channel state information at the sender and/or the receiver. In our work, we focus on infinite-state Markov channels by investigating the problem of message transmission over time-varying single-user multiple-input multiple-output (MIMO) Gauss-Markov Rayleigh fading channels, as an example of MIMO ergodic Rayleigh fading channels, with average power constraint and with complete channel state information available at the receiver side (CSIR). We prove a single-letter formula for the channel capacity and in particular the formula pointed out by Telatar for the channel capacity of MIMO ergodic Rayleigh fading channels for the case when the Gaussian noise is uncorrelated across antennas.

Secure communication in a potentially hostile environment is becoming more and more critical. TheArbitrarilyVaryingWiretapChannel (AVWC) provides information-theoretical bounds on how much information can be exchanged even in the presence of an active attacker. If the active attacker has non-causal side information, situations in which a legitimate communication system has been hacked can be modeled. We investigate the AVWC with non-causal side information at the jammer for the case that there exists a best channel to the eavesdropper. Non-causal side information means that the transmitted codeword is known to an active adversary before it is transmitted. By considering the maximum error criterion, we also allow messages to be known at the jammer before the corresponding codeword is transmitted. A single-letter formula for theCommonRandomness (CR)-assisted secrecy capacity is derived. Additionally, we provide a formula for the CR-assisted secrecy capacity for the cases where the channel to the eavesdropper is strongly degraded, strongly noisier, or strongly less capable with respect to the main channel. Furthermore, we compare our results to the CR-assisted secrecy capacity for the cases of maximum error criterion but without non-causal side information at the jammer (blind adversary), maximum error criterion with non-causal side information of the messages at the jammer (semi-blind adversary), and the case of average error criterion without non-causal side information at the jammer (blind adversary).

We analyze deterministic message identification via channels with non-discrete additive white noise and with a noiseless feedback link under both average power and peak power constraints. The identification task is part of Post Shannon Theory. The consideration of communication systems beyond Shannon’s approach is useful in order to increase the efficiency of information transmission for certain applications. We propose a coding scheme that first generates infinite common randomness between the sender and the receiver. If the channel has a positive message transmission feedback capacity, for given error thresholds and sufficiently large blocklength this common randomness is then used to construct arbitrarily large deterministic identification codes. In particular, the deterministic identification feedback capacity is infinite regardless of the scaling (exponential, doubly exponential, etc.) chosen for the capacity definition. Clearly, if randomized encoding is allowed in addition to the use of feedback, these results continue to hold.

This paper assesses the impact on the performance that information-theoretic physical layer security (IT-PLS) introduces when integrated into a 5G New Radio (NR) system. For this, we implement a wiretap code for IT-PLS based on a modular coding scheme that uses a universal-hash function in its security layer. The main advantage of this approach lies in its flexible integration into the lower layers of the 5G NR protocol stack without affecting the communication's reliability. Specifically, we use IT-PLS to secure the transmission of downlink control information by integrating an extra pre-coding security layer as part of the physical downlink control channel (PDCCH) procedures, thus not requiring any change of the 3GPP 38 series standard. We conduct experiments using a real-time open-source 5G NR standalone implementation and use software-defined radios for over-the-air transmissions in a controlled laboratory environment. The overhead added by IT-PLS is determined in terms of the latency introduced into the system, which is measured at the physical layer for an end-to-end (E2E) connection between the gNB and the user equipment.

We experimentally verify the information-theoretic security of a seeded modular code for the AWGN wiretap channel consisting of a security layer, an error-correction layer and a modulation layer. The security layer is given by a universal family of hash functions. In the error-correction layer and the modulation layer we use polar codes and QAM, respectively. The eavesdropper uses the maximum likelihood (ML) test as an attack strategy. We analyze the security in different communication scenarios using simulations. We show that for small blocklengths the advantage (security measure) at the eavesdropper in the corresponding scenario can be close to 0 for suitable code parameters. Additional insights gathered from the simulation results include the impact of code parameters and seed choice on security.

We study semantic security for classical-quantum channels. Our security functions are functional forms of mosaics of combinatorial designs. We extend methods in [25] from classical channels to classical-quantum channels to demonstrate that mosaics of designs ensure semantic security for classical-quantum channels, and are also capacity achieving coding schemes. An advantage of these modular wiretap codes is that we provide explicit code constructions that can be implemented in practice for every channel, given an arbitrary public code.

We investigate the problem of message transmission over time-varying single-user multiple-input multiple-output (MIMO) Rayleigh fading channels with average power constraint and with complete channel state information available at the receiver side (CSIR). To describe the channel variations over the time, we consider a first-order Gauss-Markov model. We completely solve the problem by giving a single-letter characterization of the channel capacity in closed form and by providing a rigorous proof of it.

We generalize the uniform common randomness capacity formula, initially established by Ahslwede and Csiszár for a two-source model for common randomness generation from independent and identically distributed (i.i.d.) discrete sources with unidirectional communication over rate-limited discrete noiseless channels to the case when the one-way communication is over arbitrary single-user channels. In our proof, we will make use of the transmission capacity formula established by Verdú and Han for arbitrary point-to-point channels.

Abstract We study security functions which can serve to establish semantic security for the two central problems of information-theoretic security: the wiretap channel, and privacy amplification for secret key generation. The security functions are functional forms of mosaics of combinatorial designs, more precisely, of group divisible designs and balanced incomplete block designs. Every member of a mosaic is associated with a unique color, and each color corresponds to a unique message or key value. Every block index of the mosaic corresponds to a public seed shared between the two trusted communicating parties. The seed set should be as small as possible. We give explicit examples which have an optimal or nearly optimal trade-off of seed length versus color (i.e., message or key) rate. We also derive bounds for the security performance of security functions given by functional forms of mosaics of designs.

In this paper we use a seeded modular coding scheme for implementing physical layer security in a wiretap scenario. This modular scheme consists of a traditional coding layer and a security layer. For the traditional coding layer, we use a polar code. We evaluate the performance of the seeded modular coding scheme in an experimental setup with software defined radios and compare these results to simulation results. In order to assess the secrecy level of the scheme, we employ the distinguishing security metric. In our experiments, we compare the distinguishing error rate for different seeds and block lengths.

This paper analyzes the problem of common randomness (CR) generation from correlated discrete sources aided by unidirectional communication over Single-Input Single-Output (SISO) slow fading channels with additive white Gaussian noise (AWGN) and arbitrary state distribution. Slow fading channels are practically relevant in many situations in wireless communications. We completely solve the SISO slow fading case by establishing its corresponding outage CR capacity using our characterization of its channel outage capacity. The generated CR could be exploited to improve the performance gain in the identification scheme. The latter is known to be more efficient than the classical transmission scheme in many new applications, which demand ultra-reliable low latency communication.

We analyze message identification via Gaussian channels with noiseless feedback, which is part of the Post Shannon theory. The consideration of communication systems beyond Shannon's approach is useful in order to increase the efficiency of information transmission for certain applications. If the noise variance is positive, we propose a coding scheme that generates infinite common randomness between the sender and the receiver. We show that any identification rate via the Gaussian channel with noiseless feedback can be achieved. The remarkable result is that this applies to both rate definitions $\frac{1}{n}\log M$ (as defined by Shannon for transmission) and $\frac{1}{n}\ \log \log\ M$ — (as defined by Ahlswede and Dueck for identification). We can even show that our result holds regardless of the selected scaling for the rate. A detailed version with all proofs, explanations and more discussions can be found in [1].

We study security functions which can serve to establish semantic security for privacy amplification in secret key generation. The security functions are functional forms of mosaics of combinatorial designs, more precisely, of group divisible designs and balanced incomplete block designs. Every member of a mosaic corresponds to a unique key value. We give explicit examples which have an optimal or nearly optimal tradeoff of seed size, given by the size of the block index set of the mosaics, versus key rate. We also derive bounds for the security performance in privacy amplification of security functions given by functional forms of mosaics of designs.

We investigate the problem of common randomness (CR) generation from discrete correlated sources aided by one-way communication over single-user multiple-input multiple-output (MIMO) slow fading channels with additive white Gaussian noise (AWGN), arbitrary state distribution and with channel state information available at the receiver side (CSIR). We completely solve the problem by first characterizing the channel outage capacity of MIMO slow fading channels for arbitrary state distribution. For this purpose, we also provide an achievable rate for a specific compound MIMO Gaussian channel. Second, we define the outage CR capacity of the MIMO slow fading channel and establish a single-letter characterization of it using our result on its outage transmission capacity.

A novel type of functions called biregular irreducible functions is introduced and applied as security components (instead of, e.g., universal hash functions) in seeded modular wiretap coding schemes, whose second component is an error-correcting code. These schemes are called modular BRI schemes. An upper bound on the semantic security information leakage of modular BRI schemes in a one-shot setting is derived which separates the effects of the biregular irreducible function on the one hand and the error-correcting code plus the channel on the other hand. The effect of the biregular irreducible function is described by the second-largest eigenvalue of an associated stochastic matrix. A characterization of biregular irreducible functions is given in terms of connected edge-disjoint biregular graphs. It allows for the construction of new biregular irreducible functions from families of edge-disjoint Ramanujan graphs, which are shown to exist. A concrete and frequently used arithmetic universal hash function can be converted into a biregular irreducible function for certain parameters. Sequences of Ramanujan biregular irreducible functions are constructed which exhibit an optimal trade-off between the size of the regularity set and the rate of decrease of the associated second-largest eigenvalue. Together with the one-shot bound on the information leakage, the existence of these sequences implies an asymptotic coding result for modular BRI schemes applied to discrete and Gaussian wiretap channels. It shows that the separation of error correction and security as done in a modular BRI scheme is secrecy capacity-achieving for every discrete and Gaussian wiretap channel. The same holds for a derived construction where the seed is generated locally by the sender and reused several times. It is shown that the optimal sequences of biregular irreducible functions used in the above constructions must be nearly Ramanujan.

We determine the semantic security capacity for quantum wiretap channels. We extend methods for classical channels to quantum channels to demonstrate that a strongly secure code guarantees a semantically secure code with the same secrecy rate. Furthermore, we show how to transform a non-secure code into a semantically secure code by means of biregular irreducible functions (BRI functions). We analyze semantic security for classical-quantum channels and for quantum channels.

We investigate the Arbitrarily Varying Wiretap Channel (AVWC) with non-causal side information at the jammer for the case that there exists a best channel to the eavesdropper and under the condition that strong degradedness holds. Non-causal side information means that codewords are known at an active adversary before they are transmitted. By considering the maximum error criterion, we allow also messages to be known at the jammer before the corresponding codeword is transmitted. A single letter formula for the common randomness secrecy capacity is derived.

It is investigated how to achieve semantic security for the wiretap channel. A new type of functions called biregular irreducible (BRI) functions, similar to universal hash functions, is introduced. BRI functions provide a universal method of establishing secrecy. It is proved that the known secrecy rates of any discrete and Gaussian wiretap channel are achievable with semantic security by modular wiretap codes constructed from a BRI function and an error-correcting code. A characterization of BRI functions in terms of edge-disjoint biregular graphs on a common vertex set is derived. This is used to study examples of BRI functions and to construct new ones.

The zero-error secrecy capacity of uncertain wiretap channels is defined. If the sensor-estimator channel is perfect, it is also calculated. Further properties are discussed. The problem of estimating a dynamical system with nonstochastic disturbances is studied where the sensor is connected to the estimator and an eavesdropper via an uncertain wiretap channel. The estimator should obtain a uniformly bounded estimation error whereas the eavesdropper's error should tend to infinity. It is proved that the system can be estimated securely if the zero-error capacity of the sensor-estimator channel is strictly larger than the logarithm of the system's unstable pole and the zero-error secrecy capacity of the uncertain wiretap channel is positive.

We define the common randomness-assisted capacity of an arbitrarily varying wiretap channel (AVWC) when the eavesdropper is kept ignorant about the common randomness. We prove a multi-letter capacity formula for this model. We prove that, if enough common randomness is used, the capacity formula can be given a single-shot form again. We then consider the opposite extremal case, where no common randomness is available, and derive the capacity. It is known that the capacity of the system can be discontinuous under these circumstances. We prove here that it is still stable in the sense that it is continuous around its positivity points. We further prove that discontinuities can only arise if the legal link is symmetrizable and characterize the points where it is positive. These results shed new light on the design principles of communication systems with embedded security features. At last, we investigate the effect of super-activation of the message transmission capacity of AVWCs under the average error criterion. We give a complete characterization of those AVWCs that may be super-activated. The effect is thereby also related to the (conjectured) super-activation of the common randomness assisted capacity of AVWCs with an eavesdropper that gets to know the common randomness. Super-activation is based on the idea of wasting a few bits of non-secret messages in order to enable provably secret transmission of a large bulk of data, a concept that may prove to be of further importance in the design of communication systems. In this paper, we provide further insight into this phenomenon by providing a class of codes that is capacity achieving and does not convey any information to the eavesdropper.

We give a complete characterization of the correlated random coding secrecy capacity of arbitrarily varying wiretap channels (AVWCs). We apply two alternative strong secrecy criteria, which both lead to the same multi-letter formula. The difference of these criteria lies in the treatment of correlated randomness; they coincide in the case of uncorrelated codes. On the basis of the derived formula, we show that the correlated random coding secrecy capacity is continuous as a function of the AVWC, in contrast to the discontinuous uncorrelated coding secrecy capacity. In the proof of the secrecy capacity formula for correlated random codes, we apply an auxiliary channel, which is compound from the sender to the intended receiver and arbitrarily varying from the sender to the eavesdropper.

We study the arbitrarily varying wiretap channel (AVWC) under average error criterion when external common randomness (CR) can be used between the legitimate parties. We consider three scenarios: In the first one the CR is known to the eavesdropper, in the second it is not known to her and in the third there is no CR available. For the second scenario, we prove a complete coding theorem. For the third scenario it is known that the capacity function is discontinuous. We prove that it is nonetheless stable in the sense of being continuous around its positivity points. We characterize the points of discontinuity in terms of continuous functions. We then give a complete characterization of those pairs of AVWCs whose capacity can be super-activated in the unassisted third case - in terms of the capacity function describing the first case.

We give a complete characterization of the secrecy capacity of arbitrarily varying wiretap channels (AVWCs) with correlated random coding under a strong secrecy criterion where the eavesdropper may also know the correlated randomness. We obtain that the correlated random coding secrecy capacity is continuous as a function of the AVWC. We show that the deterministic coding secrecy capacity of the AVWC either equals 0 or the correlated random coding secrecy capacity. For the case that only a weak secrecy criterion is applied, a complete characterization of the corresponding secrecy capacity for deterministic codes is possible. In the proof of the secrecy capacity formula for correlated random codes, we apply an auxiliary channel which is compound from the sender to the intended receiver and varies arbitrarily from the sender to the eavesdropper. We discuss the relation between the usual mutual information secrecy criterion and a criterion formulated in terms of total variation distance, and investigate the robustness of the AVWC model.

If the senders and the receiver of an Arbitrarily Varying Multiple-Access Channel (AV-MAC) have access to the outputs of discrete correlated memoryless sources, the same rate region is achievable as if common randomness were available. This reduces the necessary amount of cooperation in an AV-MAC considerably. Moreover, to transmit blocklength-n words, no more than order log n source outputs are required.

To increase the spectral efficiency of future wireless networks, it is important to wisely integrate multiple services at the physical layer. Here the efficient integration of confidential services in the three-node bidirectional relay channel is studied. A relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol, which is also known as two-way relaying. In the broadcast phase, the relay transmits not only the two bidirectional messages it received in the previous multiple access phase, but also an additional confidential message to one node while keeping the other node completely ignorant of it. The concept of strong information theoretic secrecy is used to ensure that the nonlegitimate node cannot decode the confidential message no matter what its computational resources are. Moreover, this implies that the average decoding error at the nonlegitimate node goes exponentially fast to one for any decoding strategy it may use. This results in the study of the bidirectional broadcast channel with confidential messages for which the strong secrecy capacity region is established. Furthermore, it is shown that the efficient integration of confidential messages with strong secrecy extends to such scenarios, where the relay further transmits an additional common message to both nodes.

We derive the capacity region of arbitrarily varying multiple-access channels (AV-MACs) with conferencing encoders for both deterministic and random coding. For a complete description, it is sufficient that one conferencing capacity is positive. We obtain a dichotomy: either the channel's deterministic capacity region is zero or it equals the 2-D random coding region. We determine exactly when either case holds. We also discuss the benefits of conferencing. We give the example of an AV-MAC which does not achieve any nonzero rate pair without encoder cooperation, but the 2-D random coding capacity region if conferencing is possible. Unlike compound multiple-access channels, arbitrarily varying multiple-access channels may exhibit a discontinuous increase of the capacity region when conferencing in at least one direction is enabled.

We derive a rate region which is achievable by the Wiretap MAC with Common Message under the strong secrecy criterion. We follow Devetak's approach to establishing strong secrecy. Using the concentration of the normed sum of bounded i.i.d. random variables around its mean, it is possible to show the existence of a code where the channel outputs at the eavesdropper are almost independent of the messages. The encoders may use a certain amount of common randomness. We give the example of a channel where the availability of common randomness is necessary for secret transmission.

We characterize the capacity region of the arbitrarily varying multiple-access channel with conferencing encoders. This channel exhibits a dichotomy: either it is useless or its capacity region equals the region achievable with random coding. We determine exactly when either case holds. This model can be used to analyze downlink networks with cooperating base stations suffering from exterior interference.

The goal of this paper is to provide a rigorous information-theoretic analysis of subnetworks of interference networks. We prove two coding theorems for the compound multiple-access channel (MAC) with an arbitrary number of channel states. The channel state information at the transmitters is such that each transmitter has a finite partition of the set of states and knows which element of the partition the actual state belongs to. The receiver may have arbitrary channel state information. The first coding theorem is for the case that both transmitters have a common message and that each has an additional private message. The second coding theorem is for the case where rate-constrained, but noiseless transmitter cooperation is possible. This cooperation may be used to exchange information about channel state information as well as the messages to be transmitted. The cooperation protocol used here generalizes Willems' conferencing. We show how this models base station cooperation in modern wireless cellular networks used for interference coordination and capacity enhancement. In particular, the coding theorem for the cooperative case shows how much cooperation is necessary in order to achieve maximal capacity in the network considered.

We characterize the capacity region of the compound Discrete Memoryless Multiple Access Channel, where both transmitters have an additional common message. The channel state information is as follows: for each transmitter, there is a finite partition of the set of channels. Each transmitter knows which element of his partition the channel actually used belongs to. The capacity region is not affected by the amount of channel state information at the receiver, which may be arbitrary.

We investigate the low-SNR sum rate performance of QPSK for symmetric interference channels. The QPSK performance is described by the minimum energy per bit and the wideband slope pertaining to the sum capacity. Comparing this with the minimum energy per bit and wideband slope of corresponding interference channels using optimal inputs, we find that QPSK achieves optimal performance in all of the cases where exact sum capacities are known. We also show that a simplified Han-Kobayashi scheme is suboptimal in the low-SNR regime when the input alphabet is the whole set of complex numbers.