Peak to average power ratio (PAPR) reduction technique in orthogonal frequency division multiplexing (OFDM) using block coding

Orthogonal Frequency Division Multiplexing (OFDM) signal is considered a good candidate for wireless systems because it offers diversity gain in frequency selective channels. As in other multicarrier schemes, however, OFDM suffers from high peak to average power ratio (PAPR). This is a major drawback of the scheme and ways of minimizing the PAPR have been researched. Block coding scheme is the technique to reduce the peak-to-average power ratio of OFDM signals and also to detect transmission errors. The reason is that in the time domain, a multicarrier signal is the sum of many narrowband signals. At some time instances, this sum is large and at other times is small, which means that the peak value of the signal is substantially larger than the average value. This high PAR is one of the most important implementation challenges that face OFDM, because it reduces the efficiency. The main purpose in this project, is to make a comparison over the PAPR reduction technique using block coding and without block coding. The capability of Block Coding scheme to reduce the Bit Error Rate (BER) in an OFDM system was also measured. The simulation developed in Matlab simulation environment

Ouroboros-E: An efficient Lattice-based Key-Exchange Protocol

The Bit Flipping algorithm is a hard decision decoding algorithm originally designed by Gallager in 1962 to decode Low Density Parity Check Codes (LDPC). It has recently proved to be much more versatile, for Moderate Parity Check Codes (MDPC) or Euclidean metric. We further demonstrate its power by proposing a noisy Euclidean version of it. This tweak allows to construct a lattice based key exchange analogous to the Ouroboros protocol for Hamming metric but with a reduction to the Short Integer Solution (SIS) problem. The very efficient decoding algorithm permits to consider smaller alphabets than for NTRU or Ring-LWE decryption algorithms. Overall we obtain a new protocol which competes with the recent NEWHOPE and Kyber proposals, and also with NTRU. The resulting scheme exploits the cyclicity of the error, and benefits from the security of the renowned SIS problem.acceptedVersio

Analysis of the security of the PSSI problem and cryptanalysis of the Durandal signature scheme

We present a new attack against the PSSI problem, one of the three problems at the root of security of Durandal, an efficient rank metric code-based signature scheme with a public key size of 15 kB and a signature size of 4 kB, presented at EUROCRYPT\u2719. Our attack recovers the private key using a leakage of information coming from several signatures produced with the same key. Our approach is to combine pairs of signatures and perform Cramer-like formulas in order to build subspaces containing a secret element. We break all existing parameters of Durandal: the two published sets of parameters claiming a security of 128 bits are broken in respectively $2^{66}$ and $2^{73}$ elementary bit operations, and the number of signatures required to finalize the attack is 1,792 and 4,096 respectively. We implemented our attack and ran experiments that demonstrated its success with smaller parameters

Towards Post-Quantum Blockchain: A Review on Blockchain Cryptography Resistant to Quantum Computing Attacks

[Abstract] Blockchain and other Distributed Ledger Technologies (DLTs) have evolved significantly in the last years and their use has been suggested for numerous applications due to their ability to provide transparency, redundancy and accountability. In the case of blockchain, such characteristics are provided through public-key cryptography and hash functions. However, the fast progress of quantum computing has opened the possibility of performing attacks based on Grover's and Shor's algorithms in the near future. Such algorithms threaten both public-key cryptography and hash functions, forcing to redesign blockchains to make use of cryptosystems that withstand quantum attacks, thus creating which are known as post-quantum, quantum-proof, quantum-safe or quantum-resistant cryptosystems. For such a purpose, this article first studies current state of the art on post-quantum cryptosystems and how they can be applied to blockchains and DLTs. Moreover, the most relevant post-quantum blockchain systems are studied, as well as their main challenges. Furthermore, extensive comparisons are provided on the characteristics and performance of the most promising post-quantum public-key encryption and digital signature schemes for blockchains. Thus, this article seeks to provide a broad view and useful guidelines on post-quantum blockchain security to future blockchain researchers and developers.10.13039/501100010801-Xunta de Galicia (Grant Number: ED431G2019/01) 10.13039/501100011033-Agencia Estatal de Investigación (Grant Number: TEC2016-75067-C4-1-R and RED2018-102668-T) 10.13039/501100008530-European Regional Development FundXunta de Galicia; ED431G2019/0

From Pre-Quantum to Post-Quantum IoT Security: A Survey on Quantum-Resistant Cryptosystems for the Internet of Things

© 2020 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[Absctract]: Although quantum computing is still in its nascent age, its evolution threatens the most popular public-key encryption systems. Such systems are essential for today's Internet security due to their ability for solving the key distribution problem and for providing high security in insecure communications channels that allow for accessing websites or for exchanging e-mails, financial transactions, digitally signed documents, military communications or medical data. Cryptosystems like Rivest-Shamir-Adleman (RSA), elliptic curve cryptography (ECC) or Diffie-Hellman have spread worldwide and are part of diverse key Internet standards like Transport Layer Security (TLS), which are used both by traditional computers and Internet of Things (IoT) devices. It is especially difficult to provide high security to IoT devices, mainly because many of them rely on batteries and are resource constrained in terms of computational power and memory, which implies that specific energy-efficient and lightweight algorithms need to be designed and implemented for them. These restrictions become relevant challenges when implementing cryptosystems that involve intensive mathematical operations and demand substantial computational resources, which are often required in applications where data privacy has to be preserved for the long term, like IoT applications for defense, mission-critical scenarios or smart healthcare. Quantum computing threatens such a long-term IoT device security and researchers are currently developing solutions to mitigate such a threat. This article provides a survey on what can be called post-quantum IoT systems (IoT systems protected from the currently known quantum computing attacks): the main post-quantum cryptosystems and initiatives are reviewed, the most relevant IoT architectures and challenges are analyzed, and the expected future trends are indicated. Thus, this article is aimed at providing a wide view of post-quantum IoT security and give useful guidelines...This work was supported in part by the Xunta de Galicia under Grant ED431G2019/01, in part by the Agencia Estatal de Investigación of Spain under Grant TEC2016-75067-C4- 1-R and Grant RED2018-102668-T, and in part by ERDF funds of the EU (AEI/FEDER, UE).Xunta de Galicia; ED431G2019/0

Equivalence and Characterizations of Linear Rank-Metric Codes Based on Invariants

We show that the sequence of dimensions of the linear spaces, generated by a given rank-metric code together with itself under several applications of a field automorphism, is an invariant for the whole equivalence class of the code. The same property is proven for the sequence of dimensions of the intersections of itself under several applications of a field automorphism. These invariants give rise to easily computable criteria to check if two codes are inequivalent. We derive some concrete values and bounds for these dimension sequences for some known families of rank-metric codes, namely Gabidulin and (generalized) twisted Gabidulin codes. We then derive conditions on the length of the codes with respect to the field extension degree, such that codes from different families cannot be equivalent. Furthermore, we derive upper and lower bounds on the number of equivalence classes of Gabidulin codes and twisted Gabidulin codes, improving a result of Schmidt and Zhou for a wider range of parameters. In the end we use the aforementioned sequences to determine a characterization result for Gabidulin codes.Comment: 37 pages, 1 figure, 3 tables, extended version of arXiv:1905.1132