In this paper, a new symmetric key cryptosystem based on linear codes is presented. Unlike most code‐based cryptosystems, the code is known publicly. The encryption is based on randomly interleaving two codewords containing random errors. This is the first code‐based cryptosystem based on random interleaving. The key size and security of the proposed scheme are analysed, and it is shown that allowing the code to be public results in a significantly smaller key than other code‐based cryptosystems. Furthermore, it is proven that the best possible chosen plaintext attack does not affect the security.

Multitemporal polarimetric synthetic aperture radar (SAR) data can be used to estimate the dominant scattering mechanism of targets in a stack of SAR data and to improve the performance of SAR interferometric methods for deformation studies. In this letter, we developed a polarimetric form of amplitude difference dispersion (ADD) criterion for time-series analysis of pixels in which interferometric noise shows negligible decorrelation in time and space in small baseline algorithm. The polarimetric form of ADD is then optimized in order to find the optimum scattering mechanism of the pixels, which in turn is used to produce new interferograms with better quality than single-pol SAR interferograms. The selected candidates are then combined with temporal coherency criterion for final phase stability analysis in full-resolution interferograms. Our experimental results derived from a data set of 17 dual polarizations X-band SAR images (HH/VV) acquired by TerraSAR-X shows that using optimum scattering mechanism in the small baseline method improves the number of pixel candidates for deformation analysis by about 2.5 times in comparison with the results obtained from single-channel SAR data. The number of final pixels increases by about 1.5 times in comparison with HH and VV in small baseline analysis. Comparison between persistent scatterer (PS) and small baseline methods shows that with regards to the number of pixels with optimum scattering mechanism, the small baseline algorithm detects 10% more pixels than PS in agricultural regions. In urban regions, however, the PS method identifies nearly 8% more coherent pixels than small baseline approach.

In this paper, a particular class of block-circulant low-density parity-check (BC-LDPC) codes referred to as cylinder-type BC-LDPC (CTBC-LDPC) codes is studied. We represent a cylinder-type parity-check matrix H by a graph called the block-structure graph of H and denoted by BSG(H). Using the properties of BSG(H) we show that CTBC matrices with column-weight two and girth an arbitrary multiple of 8 can be constructed, while for a CTBC matrix H with column-weight ℓ ≥ 3 this girth cannot exceed 12. An algorithm generating CTBC-LDPC codes of arbitrary possible girth is given. The algorithm produces a large group of codes with flexible rate, length and girth. From performance perspective over AWGN channel, the maximum girth-12 CTBC-LDPC codes with column-weight at least three generated by the given algorithm are at least as good as their random-like counterpart codes and outperform the codes of the same size constructed by successive-level-growth, progressive-edge-growth, and partition-and-shift methods.

A new class of high rate Fibonacci polynomial based error-correcting codes is introduced. For integers m; n; x ≥ 1, a square encoding matrix Q2mn(x) of order 2m and the corresponding decoding matrix Q2m-n(x) are provided. It is shown that a higher code rate is obtained than with the original Fibonacci polynomial based codes.

Multi-domain traffic engineering is a major focus area for carriers and crankback signaling offers a very promising alternative. However, even though various crankback studies have been done, there remains significant latitude for improved multi-domain designs. To address these challenges, this work develops a novel solution for intra/inter-domain signaling crankback in IP/MPLS networks. Namely, dynamic intra-domain link-state routing information is coupled with inter-domain path/distance-vector routing state to improve the search process. Mechanisms are also added to limit setup signaling overheads and track crankback history from congested links. The performance of the proposed solution is analyzed using simulation and compared against other techniques including hierarchical inter-domain routing.

Multi-domain traffic engineering is a major focus area for carriers and crankback signaling offers a very promising alternative. However, even though various crankback studies have been done, there remains significant latitude for improved multi-domain designs. To address these challenges, this work develops a novel solution for intra/inter-domain signaling crankback in IP/MPLS networks. Namely, dynamic intra-domain link-state routing information is coupled with inter-domain path/distance-vector routing state to improve the search process. Mechanisms are also added to limit setup signaling overheads and track crankback history from congested links. The performance of the proposed solution is analyzed using simulation and compared against other techniques including hierarchical inter-domain routing.

Four classes of maximum-girth geometrically structured column-weight-two regular quasi-cyclic (QC) low-density parity-check (LDPC) codes are introduced. Two classes of these codes, referred to as Type-I and Type-II codes, are with row-weights 4 and 3, and maximum girths 16 and 24, respectively. The idea behind the construction of these two classes of codes, with rates at least 1/2 and 1/3, is slightly generalized to obtain two classes of variable-high-rate codes, referred to as Type-III1 and Type-III2 codes, with maximum girth 20 and 16, respectively. A low-complexity deterministic algorithm for constructing these four classes of codes is given. The algorithm generates maximum-girth Type-I and Type-II codes with almost arbitrary length eta not less than 216 and 243, respectively. The output of the algorithm substantially improves on some of the previously best known codes constructed using a randomized progressive edge-growth (RPEG) algorithm. For instance, we have rate-0.71 Type-III1 codes of lengths 308 and 728 with girths 10 and 12, respectively, versus the code lengths 385 and 840 obtained by the RPEG algorithm. Simulation results on AWGN channel confirm that, from BER performance perspective, the constructed LDPC codes are superior to the column-weight-two LDPC codes constructed by the previously reported methods. The generator matrix G(D) of the convolutional codes associated with Type-I and Type-II codes is given. The free distance dfreeof such a convolutional code is equal to the minimum distance of the corresponding QC block code.

A class of maximum-girth geometrically structured regular (n, 2, k≥5) (column-weight 2 and row-weight k) quasi-cyclic low-density parity-check (LDPC) codes is presented. The method is based on cylinder graphs and the slope concept. It is shown that the maximum girth achieved by these codes is 12. A low-complexity algorithm producing all such maximum-girth LDPC codes is given. The shortest constructed code has a length of 105. The minimum length n of a regular (2, k) LDPC code with girth g=12 determined by the Gallager bound has been achieved by the constructed codes. From the perspective of performance these codes outperform the column-weight 2 LDPC codes constructed by the previously reported methods. These codes can be encoded using an erasure decoding process.