A novel approach to security enhancement of chaotic DSSS systems

In this paper, we propose a novel approach to the enhancement of physical layer security for chaotic direct-sequence spread-spectrum (DSSS) communication systems. The main idea behind our proposal is to vary the symbol period according to the behavior of the chaotic spreading sequence. As a result, the symbol period and the spreading sequence vary chaotically at the same time. This simultaneous variation aims at protecting DSSS-based communication systems from the blind estimation attacks in the detection of the symbol period. Discrete-time models for spreading and despreading schemes are presented and analyzed. Multiple access performance of the proposed technique in the presence of additional white Gaussian noise (AWGN) is determined by computer simulations. The increase in security at the physical layer is also evaluated by numerical results. Obtained results show that our proposed technique can protect the system against attacks based on the detection of the symbol period, even if the intruder has full information on the used chaotic sequence.Peer ReviewedPostprint (author's final draft

On the Cryptographic Strength of Symmetric Ciphers Suitable for Power-Line Communications Abstract

Power-line communications (PLC) use publicly accessible power-lines for the transmission of data. The powerline should be viewed as a hostile channel requiring special security services, if secure communication is desired. This paper introduces cryptography and related services. The operation and characteristics of some symmetric block ciphers for PLC use are reviewed. These characteristics include security, speed and flexibility. Exhaustive key search is suggested as a first yardstick for the security of ciphers and a minimal key length to provide adequate security is proposed. Differential and linear cryptanalysis are presented as powerful attacks on the security of symmetric ciphers. The paper concludes with a tabulated list of potential symmetric ciphers for PLC applications

Applying linear cryptanalysis to ciphers with key-dependant operations

Linear cryptanalysis has been proven to be a powerful attack that can be applied to a number of symmetric block ciphers. However, conventional linear cryptanalysis is ineffective in attacking ciphers that use key-dependent operations, such as ICE, Lucifer and SAFER. In this paper conditional linear cryptanalysis, which uses characteristics that depend on some key-bit values, is introduced. This technique and its application to symmetric ciphers are analysed. The consequences of using key-dependent characteristics are explained and a formal notation of conditional linear cryptanalysis is presented. As a case study, conditional linear cryptanalysis is applied to the ICE cipher, which uses key-dependant operations to improve resistance against cryptanalysis. A successful attack on ThinICE using the new technique is presented. Further, experimental work supporting the effectiveness of conditional linear cryptanalysis is also detailed.

Automated Verification of Wireless Security Protocols using Layered Proving Trees

Abstract:- Cryptographic protocols are designed to provide security services, such as key distribution, authentication and non-repudiation, over insecure networks. Formal verification of these protocols is an important step in their design. The manual verification of security protocols using logic-based formal methods is susceptible to human-factor errors in correctly applying logical postulates. Using automated systems, which apply the axioms of the logic as part of the proving process, has the potential to improve the verification process. This paper presents an empirical study of an automated proving system on the analysis of two wireless communication protocols. The automated system uses the CS modal logic implemented on a layered proving tree-based proving engine. The analysis demonstrates the accuracy of the automated systems in finding protocol flaws. Also the system is shown to be efficient both in terms of time and memory resources. Key-Words:- automated formal verification, modal logics, wireless communication, security protocol.

Experimental assessment of FIRO- and GARO-based noise sources for digital TRNG designs on FPGAs

The quality of TRNG designs mainly depends on the grade of the noise source from which the entropy will be harvested to extract randomness. Especially for purely digital noise sources suitable for FPGA implementations the use of Ring Oscillators is suggested in many scientific publications. Standard Ring Oscillator based noise sources however have earned some criticism regarding the amount of entropy generated. On this account different enhancements have been proposed, with Fibonacci Ring Oscillators (FIROs) and Galois Ring Oscillators (GAROs) being prominent examples, which under some circumstances are able to sustain a chaotic oscillation suitable for entropy extraction. This paper deals with the assessment of fully constrained FIRO and GARO noise source designs for a specific target FPGA. Due to the restrictive placement of ring elements the assessment yielded new criteria for choosing proper FIRO/GARO feedback configurations and an enhanced sampling method for entropy extraction has been derived