| 1. |
- Andersson, Mattias, 1980-
(författare)
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Coding and Transmission Strategies for Secrecy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we consider several problems relating to information theoretic security. The wiretap channel is the simplest information theoretic setting which takes security into account, and in the first chapters of the thesis we design some practical coding schemes for this channel model.First we consider the design of two edge type low density parity check (LDPC) codes for the binary erasure wiretap channel (BEC-WT). For the scenario when the main channel is error free and the wiretapper's channel is a binary erasure channel (BEC) we find secrecy capacity achieving code sequences based on standard LDPC code sequences for the BEC. However, this construction does not work when there are also erasures on the main channel. For this case we develop a method based on linear programming to optimize two edge type degree distributions. Using this method we find code ensembles that perform close to the secrecy capacity of the BEC-WT. We generalize a method of Méasson, Montanari, and Urbanke in order to compute the conditional entropy of the message at the wiretapper. We apply this method to relatively simple ensembles and find very good secrecy performance.We then show that Arikan's polar codes can be used to achieve the whole capacity-equivocation region of for any degraded symmetric binary input wiretap channel. We also design capacity achieving polar codes for the decode-and-forward scheme for the physically degraded relay channel, and for the bidirectional broadcast channel with common and confidential messages.In the subsequent chapter we consider a Gaussian system model. We show that sparse regression codes (SPARCS) as introduced by Joseph and Barron achieve the secrecy capacity of the additive white Gaussian noise (AWGN) wiretap channel, and can be used to implement the decode-and-forward scheme for the Gaussian relay channel. We also consider secret key agreement using correlated Gaussian random variables and a rate-limited public channel. We show that SPARCs attain the capacity region also for this problem.Finally we consider secret key agreement over reciprocal fading channels. We first consider a multiple-antenna setup in the high signal-to-noise-ratio (SNR) regime and propose a scheme based on training and randomness sharing. We then consider a single antenna setup in the low SNR regime, where one of the terminals is only allowed to transmit pilot signals. We propose a bursty transmission scheme based on training and opportunistic transmission using a wiretap channel code, and show that this scheme is optimal.
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| 2. |
- Andersson, Mattias
(författare)
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Coding for the Wiretap Channel
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We consider code design for Wyner’s wiretap channel. Optimal coding schemes for this channel require an overall code that is capacity achieving for the main channel, partitioned into smaller subcodes, all of which are capacity achieving for the wiretapper’s channel. To accomplish this we introduce two edge type low density parity check (LDPC) ensembles for the wiretap channel. For the scenario when the main channel is error free and the wiretapper’s channel is a binary erasure channel (BEC) we find secrecy capacity achieving code sequences based on standard LDPC code sequences for the BEC. However, this construction does not work when there are also erasures on the main channel. For this case we develop a method based on linear programming to optimize two edge type degree distributions. Using this method we find code ensembles that perform close to the secrecy capacity of the binary erasure wiretap channel (BEC- WT). We generalize a method of M ́easson, Montanari, and Urbanke in order to compute the conditional entropy of the message at the wire- tapper. This conditional entropy is a measure of how much information is leaked to the wiretapper. We apply this method to relatively simple ensembles and find that they show very good secrecy performance. Based on the work of Kudekar, Richardson, and Urbanke, which showed that regular spatially coupled codes are capacity achieving for the BEC, we construct a regular two edge type spatially coupled ensem- ble. We show that this ensemble achieves the whole capacity-equivocation region for the BEC-WT. We also find a coding scheme using Arıkans polar codes. These codes achieve the whole capacity-equivocation region for any symmetric binary input wiretap channel where the wiretapper’s channel is degraded with respect to the main channel.
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| 3. |
- Andersson, Mattias, 1980-, et al.
(författare)
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Equivocation of Eve using two edge type LDPC codes for the binary erasure wiretap channel
- 2010
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Ingår i: 2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers (ASILOMAR). - 9781424497225 ; , s. 2045-2049
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Konferensbidrag (refereegranskat)abstract
- We consider transmission over a binary erasure wiretap channel using the code construction method introduced by Rathi et al. based on two edge type Low-Density Parity-Check (LDPC) codes and the coset encoding scheme. By generalizing the method of computing conditional entropy for standard LDPC ensembles introduced by Méasson, Montanari, and Urbanke to two edge type LDPC ensembles, we show how the equivocation for the wiretapper can be computed. We find that relatively simple constructions give very good secrecy performance and are close to the secrecy capacity.
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| 4. |
- Andersson, Mattias, et al.
(författare)
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Nested Polar Codes for Wiretap and Relay Channels
- 2010
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Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 14:8, s. 752-754
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Tidskriftsartikel (refereegranskat)abstract
- We show that polar codes asymptotically achieve the whole capacity-equivocation region for the wiretap channel when the wiretapper's channel is degraded with respect to the main channel, and the weak secrecy notion is used. Our coding scheme also achieves the capacity of the physically degraded receiver-orthogonal relay channel. We show simulation results for moderate block length for the binary erasure wiretap channel, comparing polar codes and two edge type LDPC codes.
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| 5. |
- Andersson, Mattias, 1980-, et al.
(författare)
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Nonlinear distributed sensing for closed-loop control over Gaussian channels
- 2011
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Ingår i: Communication Technologies Workshop (Swe-CTW), 2011 IEEE Swedish. - : IEEE conference proceedings. - 9781457718779 ; , s. 19-23
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Konferensbidrag (refereegranskat)abstract
- A scenario of distributed sensing for networked control systems is considered and a new approach to distributed sensing and transmission is presented. The state process of a scalar first order linear time invariant dynamical system is sensed by a network of wireless sensors, which then instantaneously transmit their measurements to a remotely situated control unit over parallel Gaussian channels. The control unit aims to stabilize the system in mean square sense. The proposed non-linear delay-free sensing and transmission strategy is compared with the well-known amplify-and-forward strategy, using the LQG control cost as a figure of merit. It is demonstrated that the proposed nonlinear scheme outperforms the best linear scheme even when there are only two sensors in the network. The proposed sensing and transmission scheme can be implemented with a reasonable complexity and it is shown to be robust to the uncertainties in the knowledge of the sensors about the statistics of the measurement noise and the channel noise.
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| 6. |
- Andersson, Mattias, et al.
(författare)
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Polar codes for bidirectional broadcast channels with common and confidential messages
- 2012
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Ingår i: International Symposium on Wireless Communication Systems (ISWCS), 2012. - : IEEE conference proceedings. - 9781467307604 ; , s. 1014-1018
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Konferensbidrag (refereegranskat)abstract
- We consider the bidirectional broadcast channel with common and confidential messages. We show that polar codes achieve the capacity of binary input symmetrical bidirectional broadcast channels with confidential messages, if one node's channel is a degraded version of the other node's channel. We also find a new bound on the cardinality of the auxiliary random variable in this setup.
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| 7. |
- Andersson, Mattias, et al.
(författare)
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Polar Coding for Bidirectional Broadcast Channels with Common and Confidential Messages
- 2013
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Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 31:9, s. 1901-1908
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Tidskriftsartikel (refereegranskat)abstract
- The integration of multiple services such as the transmission of private, common, and confidential messages at the physical layer is becoming important for future wireless networks in order to increase spectral efficiency. In this paper, bidirectional relay networks are considered, in which a relay node establishes bidirectional communication between two other nodes using a decode-and-forward protocol. In the broadcast phase, the relay transmits additional common and confidential messages, which then requires the study of the bidirectional broadcast channel (BBC) with common and confidential messages. This channel generalizes the broadcast channel with receiver side information considered by Kramer and Shamai. Low complexity polar codes are constructed that achieve the capacity region of both the degraded symmetric BBC, and the BBC with common and confidential messages. The use of polar codes allows an intuitive interpretation of how to incorporate receiver side information and secrecy constraints as different sets of frozen bits at the different receivers for an optimal code design. In order to show that the constructed codes achieve capacity, a tighter bound on the cardinality of an auxiliary random variable used in the converse is found using a method by Salehi.
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| 8. |
- Andersson, Mattias, 1980-, et al.
(författare)
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Secret-key agreement over a non-coherent block-fading MIMO wiretap channel
- 2012
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Ingår i: Information Theory Workshop (ITW), 2012 IEEE. - : IEEE. - 9781467302234 ; , s. 153-157
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Konferensbidrag (refereegranskat)abstract
- We study secret-key agreement over a non-coherent block-fading multiple input multiple output (MIMO) wiretap channel. We give an achievable scheme based on training and source emulation and analyze the rate in the high SNR regime. Based on this analysis we find the optimal number of antennas to use for training. Our main result is that if the sum of the number of antennas at Alice and Bob is larger than the coherence time of the channel, the achievable rate does not depend on the number of antennas at Eve. In this case source emulation is not needed, and using only training is optimal. We also consider the case when there is no public channel available. In this case we show that secret-key agreement is still possible by using the wireless channel for discussion, giving the same number of secure degrees of freedom as in the case with a public channel.
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| 9. |
- Andersson, Mattias, et al.
(författare)
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Secure key agreement over reciprocal fading channels in the low SNR regime
- 2013
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Ingår i: 2013 IEEE 14th Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - : IEEE. - 9781467355773 ; , s. 674-678
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Konferensbidrag (refereegranskat)abstract
- We study the low SNR scaling of the non-coherent secret-key agreement capacity over a reciprocal, block-fading channel. For the restricted class of strategies, where one of the nodes is constrained to transmit pilot-only symbols, we show that the secret-key capacity scales as SNR ·log T if T ≤ 1/SNR, where T denotes the coherence period, and as SNR·log(1/SNR) otherwise. Our upper bound is inspired by the genie-aided argument of Borade and Zheng (IT-Trans 2010). Our lower bound is based on bursty communication, channel training, and secret message transmission.
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| 10. |
- Andersson, Tomas, et al.
(författare)
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A COVQ-Based image coder for channels with bit errors and erasures
- 2008
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Ingår i: IEEE Transactions on Communications. - : IEEE Communications Society. - 0090-6778 .- 1558-0857. ; 56:2, s. 161-165
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Tidskriftsartikel (refereegranskat)abstract
- We illustrate how channel optimized vector quantization (COVQ) can be used for channels with both bit-errors and bit-erasures. First, a memoryless channel model is presented, and the performance of COVQ's trained for this channel is evaluated for an i.i.d. Gaussian source. Then, the new method is applied in implementing an error-robust sub-band image coder, and we present image results that illustrate the resulting performance. Our experiments show that the new approach is able to outperform a traditional scheme based on separate source and channel coding.
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