In this letter, we consider a wiretap channel when a source node maintains two buffers (queues) to store its data and secret key packets. We propose two medium-access protocols. In the first proposed protocol, we assume that the legitimate source and its destination share random secret key packets when the main channel is better than either the channel between the eavesdropper and the source or the channel between the eavesdropper and the destination. These key packets are stored in a separate key queue at the source and its destination, and they are utilized to secure data packets whenever channel conditions favor eavesdropper channels over the main communication channel. In the second proposed protocol, the source employs a random-access scheme based on the link and queue states. Our numerical results demonstrate the gains of our proposed protocols in terms of the mean service rate of the data queue and the average queueing delay of the data packets.
In this letter, we consider a wiretap channel when a source node maintains two buffers (queues) to store its data and secret key packets. We propose two medium-access protocols. In the first proposed protocol, we assume that the legitimate source and its destination share random secret key packets when the main channel is better than either the channel between the eavesdropper and the source or the channel between the eavesdropper and the destination. These key packets are stored in a separate key queue at the source and its destination, and they are utilized to secure data packets whenever channel conditions favor eavesdropper channels over the main communication channel. In the second proposed protocol, the source employs a random-access scheme based on the link and queue states. Our numerical results demonstrate the gains of our proposed protocols in terms of the mean service rate of the data queue and the average queueing delay of the data packets.
We consider a single-user, single-hop wireless communication system, in which data packets arrive at a data queue to be transmitted to a receiver over a block fading channel, privately from an eavesdropper. We assume that the eavesdropper listens to the transmitter over another independently fading channel and that the transmitter only has knowledge of the distribution of the eavesdropper's channel. We propose a joint secrecy rate, transmission, and admission controller based on a simple index policy that only relies on the distribution of the eavesdropper's channel rate. Given any arrival sample path, we show that our controller achieves the maximum possible data admission rate, while keeping the data queue stable as well as meeting an upper bound on the rate of secrecy outage, i.e., the fraction of data packets that are in part or fully decodable by the eavesdropper. While the solution is not unique, i.e., there are other schemes that can achieve the aforementioned performance, we show that our scheme also achieves a low queuing delay for the data packets enqueued at the data queue by striking the correct balance between direct secrecy encoding for data bits and secret key generation and utilization. To obtain this result, our transmission controller makes use of the secret key queue to smooth out the variations in the achievable secrecy rate of the associated fading wiretap channel.
In recent years, the famous wiretap channel has been revisited by many researchers and information theoretic secrecy has become an active area of research in this setting. In this paper, we design a wireless communication system that achieves constant bit rate data transmission over a block fading channel, securely from an eavesdropper that listens to the transmitter over another independent block fading channel. It is well known that, the method of sending secure information using the binning techniques inspired by the wiretap channel fails to secure the information at times when the eavesdropper channel has favorable conditions over the main channel. This phenomenon is called secrecy outage. In our system, however, we exploit the times at which the main channel is favorable over the eavesdropper channel for us to be able to transmit some random secret key bits along with the data bits. These key bits are stored in a separate key queue at the transmitter as well as the receiver, and are utilized to secure data bits, whenever the channel conditions favor the eavesdropper. We show that, our system achieves a high performance at any given desired outage probability by jointly controlling the key queue and the transmit power. We show that the optimal power control involves a time sharing between secure waterfilling and channel inversion strategies and the key queue operates in the heavy traffic regime to achieve the maximum delay limited rate possible, under a small outage constraint. This work can be viewed as a first step in providing a framework that combines both information theory and queueing analysis for the study of information theoretic security.
This paper considers the design of practical schemes that enable two terminals, namely a source and a destination, to agree on a secret key in the presence of an eavesdropper (wire-tapper). The channel model considered is a fast Rayleigh fading wiretap channel with the constraints of quadrature phase-shift-keyed source symbols and hard-decision destination quantization. It is assumed that there exists a public feedback channel between the source and destination to facilitate the key-agreement process, however, any communication over the public channel is perfectly observed by the wiretapper. A key-agreement scheme employing irregular low-density parity-check (LDPC) codes is proposed, and its secrecy performance is measured in terms of the key rate between the source and destination and the leakage rate about the secret key at the wiretapper. A code search algorithm is also developed to design irregular LDPC codes to achieve good secrecy performance under various channel conditions.
This paper studies the problem of secure communication over a wiretap channel p(y,z|x) with a secure feedback link of rate Rf, where X is the channel input, and Y and Z are channel outputs observed by the legitimate receiver and the eavesdropper, respectively. It is shown that the secrecy capacity, the maximum data rate of reliable communication while the intended message is not revealed to the eavesdropper, is upper bounded as Cs(Rf) les maxmin/p(x) {I(X;Y), I(X;Y |Z) + Rf}. The proof of the bound crucially depends on a recursive argument which is used to obtain the single-letter characterization. This upper bound is shown to be tight for the class of physically degraded wiretap channels. A capacity-achieving coding scheme is presented for this case, in which the receiver securely feeds back fresh randomness with rate Rf, generated independent of the received channel output symbols. The transmitter then uses this shared randomness as a secret key on top of Wyner's coding scheme for wiretap channels without feedback. Hence, when a feedback link is available, the receiver should allocate all resources to convey a new key rather than sending back the channel output.
In this paper, we consider a single-user secure data communication system. Data packets arriving at the transmitter are enqueued at a data queue to be transmitted to the receiver over a block fading channel, securely from an eavesdropper that listens to the transmitter over another independent block fading channel. We address two separate problems, both of which involve the maximization of a long-term average utility, defined as a function of the number of secure packets transmitted in each time slot. We propose a transmission controller and an admission controller based on simple index policies that do not rely on any prior statistical information on the data arrival process. The former chooses a random key generation (and transmission) rate as well as the secure data transmission rate in each time slot. Part of the data is secured by the available secrecy rate while the other part is encrypted by the key bits, enqueued at both the transmitter and the receiver. The latter chooses the amount of data admitted by the transmitter to be enqueued in the data queue. We show that our controller pair has a provably efficient performance. Also, we illustrate via simulations that the use of a key queue reduces the queuing delay for the data packets, while serving packets that are admitted at the maximum admissible rate. To our best knowledge, this is the first work that addresses the queuing delay in the context of secrecy.
The wiretap channel with secret keys models the problem of secure communication in the presence of a non-legitimate eavesdropper, where the transmitter and legitimate receiver share a secret key of finite rate. This communication scenario is studied for compound channels. An achievable strong secrecy rate is presented and a multi-letter upper bound is derived. For degraded compound wiretap channels with secret keys the strong secrecy capacity is established. Finally, the case of channel state information at the transmitter is discussed and the secrecy capacity is established for this case as well.