Marco Baldi | Seat - Academia.edu (original) (raw)
Papers by Marco Baldi
In this paper, a new variant of the McEliece cryptosystem, based on quasi-cyclic low-density pari... more In this paper, a new variant of the McEliece cryptosystem, based on quasi-cyclic low-density parity-check (QC-LDPC) codes, is studied. In principle, such codes can substitute Goppa codes, originally used by McEliece; their adoption, however, is subject to cryptanalytic evaluation to ensure sufficient system robustness. The authors conclude that some families of QC-LDPC codes, based on circulant permutation matrices, are inapplicable in this context, due to security issues, whilst other codes, based on the "difference families" approach, can be able to ensure a good level of security against intrusions, even if very large lengths are needed.
We improve our proposal of a new variant of the McEliece cryptosystem based on QC-LDPC codes. The... more We improve our proposal of a new variant of the McEliece cryptosystem based on QC-LDPC codes. The original McEliece cryptosystem, based on Goppa codes, is still unbroken up to now, but has two major drawbacks: long key and low transmission rate. Our variant is based on QC-LDPC codes and is able to overcome such drawbacks, while avoiding the known attacks. Recently, however, a new attack has been discovered that can recover the private key with limited complexity. We show that such attack can be avoided by changing the form of some constituent matrices, without altering the remaining system parameters. We also propose another variant that exhibits an overall increased security level. We analyze the complexity of the encryption and decryption stages by adopting efficient algorithms for processing large circulant matrices. The Toom-Cook algorithm and the short Winograd convolution are considered, that give a significant speed-up in the cryptosystem operations.
International Journal of Digital Multimedia Broadcasting, 2008
Abstract We consider a particular class of ad-hoc sensor networks, in which information must be... more Abstract We consider a particular class of ad-hoc sensor networks, in which information must be exchanged among nodes in order the value at each node to converge to the average of the sensed quantity. Several algorithms have been proposed to accomplish this task, based ...
IEEE Transactions on Broadcasting, 2009
LDPC codes are state-of-art error correcting codes, included in several standards for broadcast t... more LDPC codes are state-of-art error correcting codes, included in several standards for broadcast transmissions. Iterative soft-decision decoding algorithms for LDPC codes reach excellent error correction capability; their performance, however, is strongly affected by finite-precision issues in the representation of inner variables. Great attention has been paid, in recent literature, to the topic of quantization for LDPC decoders, but mostly focusing on binary modulations and analysing finite precision effects in a disaggregrated manner, i.e., considering separately each block of the receiver. Modern telecommunication standards, instead, often adopt high order modulation schemes, e.g. M-QAM, with the aim to achieve large spectral efficiency. This puts additional quantization problems, that have been poorly debated in previous literature. This paper discusses the choice of suitable quantization characteristics for both the decoder messages and the received samples in LDPC-coded systems using M-QAM schemes. The analysis involves also the demapper block, that provides initial likelihood values for the decoder, by relating its quantization strategy with that of the decoder. A new demapper version, based on approximate expressions, is also presented, that introduces a slight deviation from the ideal case but yields a low complexity hardware implementation.
We discuss some theoretical models for vital signs monitoring by using a UWB radar. Focusing atte... more We discuss some theoretical models for vital signs monitoring by using a UWB radar. Focusing attention on the respiration and heartbeat signals, we show the impact of relevant parameters, like the sampling time interval, on the ability to extract the desired signal parameters from the waveforms elaborated at the receiver. The role of the UWB pulse shape is also highlighted. With reference to more refined methods based on signal correlation, we propose a variant that does not need the availability of a locally generated reference signal and achieves good resolution for the movement detection, while ensuring limited processing times.
Computing Research Repository, 2010
This paper is a first study on the usage of non-systematic codes based on scrambling matrices for... more This paper is a first study on the usage of non-systematic codes based on scrambling matrices for physical layer security. The chance of implementing transmission security at the physical layer is known since many years, but it is now gaining an increasing interest due to its several possible applications. It has been shown that channel coding techniques can be effectively exploited for designing physical layer security schemes, in such a way that an unauthorized receiver, experiencing a channel different from that of the authorized receiver, is not able to gather any information. Recently, it has been proposed to exploit puncturing techniques in order to reduce the security gap between the authorized and unauthorized channels. In this paper, we show that the security gap can be further reduced by using non-systematic codes, able to scramble information bits within the transmitted codeword.
IEEE Communications Letters, 2009
This letter proposes a new class of serially concatenated codes that can be viewed as low-density... more This letter proposes a new class of serially concatenated codes that can be viewed as low-density parity- check (LDPC) codes. They are derived from multiple serially concatenated single parity-check (M-SC-SPC) codes, but they use different components, that we call multiple parity-check (MPC) codes. In comparison with M-SC-SPC codes, the new scheme achieves better performance with similar complexity. The proposed codes can represent an alternative to the well-known family of repeat accumulate (RA) codes, being based on the same principles.
This paper presents a new class of easily invertible circulant matrices, defined by exploiting th... more This paper presents a new class of easily invertible circulant matrices, defined by exploiting the isomorphism from the ring Mn of n times n circulant matrices over GF(p) to the ring Rn = GF(p)[x]/(xn - 1) of the polynomials modulo (xn - 1). Such class contains matrices free of 4-length cycles that, if sparse, can be included in the parity check matrix of QC-LDPC codes. Bounds for the weight of their inverses are also determined, that are useful for designing sparse generator matrices for these error correcting codes.
IEEE Transactions on Information Theory, 2008
This paper investigates some theoretical issues related with the truncation of maximum length seq... more This paper investigates some theoretical issues related with the truncation of maximum length sequences. It is shown that truncation can have a significant impact on the autocorrelation properties, mining the applicability of these sequences in practical applications. First and second order statistics for the autocorrelation function are considered, and some new relations are presented that simplify computation. As an example of practical impairment, we focus on space communication links and we consider the changes that occur in the transmitted waveform power spectral density when truncated sequences are used for data randomization.
Under some circumstances, the power flux density pro-duced by emissions from a spacecraft suffers... more Under some circumstances, the power flux density pro-duced by emissions from a spacecraft suffers the presence of spurious frequencies. This occurs, for example, when idle data with long sequences of zeros are transmitted. At high data rates, randomizers may not be able to ...
This paper deals with the problem of designing good rate-variable LDPC codes for wireless applica... more This paper deals with the problem of designing good rate-variable LDPC codes for wireless applications, where fast link adaptation is required in order to maximize the system efficiency. In particular, we show that the so-called "pseudo-puncturing" strategy, recently introduced, can be used as a valid alternative to more conventional solutions, by ensuring good performance while maintaining limited complexity
The goal of this paper is to evaluate the efficiency of three versions of the well known gossip a... more The goal of this paper is to evaluate the efficiency of three versions of the well known gossip algorithm, namely: basic gossip, push-sum and broadcast, for the distributed solution of averaging problems. The main focus is on the impact of link failures that, reducing the network connectivity, decrease the convergence speed. As a similar effect occurs in non fully-meshed networks, because of a limited coverage radius of the nodes, a comparison is made between these two scenarios. The considered algorithms can require optimization of some share factors; to this purpose, we resort to simulations, but the conclusions achieved are confirmed through analytical arguments, exploiting the concept of potential function.
Abstract: Binary cyclic codes achieve good error correction performance and allow the implementat... more Abstract: Binary cyclic codes achieve good error correction performance and allow the implementation of very simple encoder and decoder circuits. Among them, BCH codes represent a very important class of t-error correcting codes, with known structural properties and error correction ...
In this paper, a new variant of the McEliece cryptosystem, based on quasi-cyclic low-density pari... more In this paper, a new variant of the McEliece cryptosystem, based on quasi-cyclic low-density parity-check (QC-LDPC) codes, is studied. In principle, such codes can substitute Goppa codes, originally used by McEliece; their adoption, however, is subject to cryptanalytic evaluation to ensure sufficient system robustness. The authors conclude that some families of QC-LDPC codes, based on circulant permutation matrices, are inapplicable in this context, due to security issues, whilst other codes, based on the "difference families" approach, can be able to ensure a good level of security against intrusions, even if very large lengths are needed.
We improve our proposal of a new variant of the McEliece cryptosystem based on QC-LDPC codes. The... more We improve our proposal of a new variant of the McEliece cryptosystem based on QC-LDPC codes. The original McEliece cryptosystem, based on Goppa codes, is still unbroken up to now, but has two major drawbacks: long key and low transmission rate. Our variant is based on QC-LDPC codes and is able to overcome such drawbacks, while avoiding the known attacks. Recently, however, a new attack has been discovered that can recover the private key with limited complexity. We show that such attack can be avoided by changing the form of some constituent matrices, without altering the remaining system parameters. We also propose another variant that exhibits an overall increased security level. We analyze the complexity of the encryption and decryption stages by adopting efficient algorithms for processing large circulant matrices. The Toom-Cook algorithm and the short Winograd convolution are considered, that give a significant speed-up in the cryptosystem operations.
International Journal of Digital Multimedia Broadcasting, 2008
Abstract We consider a particular class of ad-hoc sensor networks, in which information must be... more Abstract We consider a particular class of ad-hoc sensor networks, in which information must be exchanged among nodes in order the value at each node to converge to the average of the sensed quantity. Several algorithms have been proposed to accomplish this task, based ...
IEEE Transactions on Broadcasting, 2009
LDPC codes are state-of-art error correcting codes, included in several standards for broadcast t... more LDPC codes are state-of-art error correcting codes, included in several standards for broadcast transmissions. Iterative soft-decision decoding algorithms for LDPC codes reach excellent error correction capability; their performance, however, is strongly affected by finite-precision issues in the representation of inner variables. Great attention has been paid, in recent literature, to the topic of quantization for LDPC decoders, but mostly focusing on binary modulations and analysing finite precision effects in a disaggregrated manner, i.e., considering separately each block of the receiver. Modern telecommunication standards, instead, often adopt high order modulation schemes, e.g. M-QAM, with the aim to achieve large spectral efficiency. This puts additional quantization problems, that have been poorly debated in previous literature. This paper discusses the choice of suitable quantization characteristics for both the decoder messages and the received samples in LDPC-coded systems using M-QAM schemes. The analysis involves also the demapper block, that provides initial likelihood values for the decoder, by relating its quantization strategy with that of the decoder. A new demapper version, based on approximate expressions, is also presented, that introduces a slight deviation from the ideal case but yields a low complexity hardware implementation.
We discuss some theoretical models for vital signs monitoring by using a UWB radar. Focusing atte... more We discuss some theoretical models for vital signs monitoring by using a UWB radar. Focusing attention on the respiration and heartbeat signals, we show the impact of relevant parameters, like the sampling time interval, on the ability to extract the desired signal parameters from the waveforms elaborated at the receiver. The role of the UWB pulse shape is also highlighted. With reference to more refined methods based on signal correlation, we propose a variant that does not need the availability of a locally generated reference signal and achieves good resolution for the movement detection, while ensuring limited processing times.
Computing Research Repository, 2010
This paper is a first study on the usage of non-systematic codes based on scrambling matrices for... more This paper is a first study on the usage of non-systematic codes based on scrambling matrices for physical layer security. The chance of implementing transmission security at the physical layer is known since many years, but it is now gaining an increasing interest due to its several possible applications. It has been shown that channel coding techniques can be effectively exploited for designing physical layer security schemes, in such a way that an unauthorized receiver, experiencing a channel different from that of the authorized receiver, is not able to gather any information. Recently, it has been proposed to exploit puncturing techniques in order to reduce the security gap between the authorized and unauthorized channels. In this paper, we show that the security gap can be further reduced by using non-systematic codes, able to scramble information bits within the transmitted codeword.
IEEE Communications Letters, 2009
This letter proposes a new class of serially concatenated codes that can be viewed as low-density... more This letter proposes a new class of serially concatenated codes that can be viewed as low-density parity- check (LDPC) codes. They are derived from multiple serially concatenated single parity-check (M-SC-SPC) codes, but they use different components, that we call multiple parity-check (MPC) codes. In comparison with M-SC-SPC codes, the new scheme achieves better performance with similar complexity. The proposed codes can represent an alternative to the well-known family of repeat accumulate (RA) codes, being based on the same principles.
This paper presents a new class of easily invertible circulant matrices, defined by exploiting th... more This paper presents a new class of easily invertible circulant matrices, defined by exploiting the isomorphism from the ring Mn of n times n circulant matrices over GF(p) to the ring Rn = GF(p)[x]/(xn - 1) of the polynomials modulo (xn - 1). Such class contains matrices free of 4-length cycles that, if sparse, can be included in the parity check matrix of QC-LDPC codes. Bounds for the weight of their inverses are also determined, that are useful for designing sparse generator matrices for these error correcting codes.
IEEE Transactions on Information Theory, 2008
This paper investigates some theoretical issues related with the truncation of maximum length seq... more This paper investigates some theoretical issues related with the truncation of maximum length sequences. It is shown that truncation can have a significant impact on the autocorrelation properties, mining the applicability of these sequences in practical applications. First and second order statistics for the autocorrelation function are considered, and some new relations are presented that simplify computation. As an example of practical impairment, we focus on space communication links and we consider the changes that occur in the transmitted waveform power spectral density when truncated sequences are used for data randomization.
Under some circumstances, the power flux density pro-duced by emissions from a spacecraft suffers... more Under some circumstances, the power flux density pro-duced by emissions from a spacecraft suffers the presence of spurious frequencies. This occurs, for example, when idle data with long sequences of zeros are transmitted. At high data rates, randomizers may not be able to ...
This paper deals with the problem of designing good rate-variable LDPC codes for wireless applica... more This paper deals with the problem of designing good rate-variable LDPC codes for wireless applications, where fast link adaptation is required in order to maximize the system efficiency. In particular, we show that the so-called "pseudo-puncturing" strategy, recently introduced, can be used as a valid alternative to more conventional solutions, by ensuring good performance while maintaining limited complexity
The goal of this paper is to evaluate the efficiency of three versions of the well known gossip a... more The goal of this paper is to evaluate the efficiency of three versions of the well known gossip algorithm, namely: basic gossip, push-sum and broadcast, for the distributed solution of averaging problems. The main focus is on the impact of link failures that, reducing the network connectivity, decrease the convergence speed. As a similar effect occurs in non fully-meshed networks, because of a limited coverage radius of the nodes, a comparison is made between these two scenarios. The considered algorithms can require optimization of some share factors; to this purpose, we resort to simulations, but the conclusions achieved are confirmed through analytical arguments, exploiting the concept of potential function.
Abstract: Binary cyclic codes achieve good error correction performance and allow the implementat... more Abstract: Binary cyclic codes achieve good error correction performance and allow the implementation of very simple encoder and decoder circuits. Among them, BCH codes represent a very important class of t-error correcting codes, with known structural properties and error correction ...