• Journal of Information Processing Systems
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• 제9권2호
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• pp.271-286
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• 2013

Recently, a pixel-chaotic-shuffling (PCS) method has been proposed by Huang et al. for encrypting color images using multiple chaotic systems like the Henon, the Lorenz, the Chua, and the Rossler systems. All of which have great encryption performance. The authors claimed that their pixel-chaotic-shuffle (PCS) encryption method has high confidential security. However, the security analysis of the PCS method against the chosen-plaintext attack (CPA) and known-plaintext attack (KPA) performed by Solak et al. successfully breaks the PCS encryption scheme without knowing the secret key. In this paper we present an improved shuffling pattern for the plaintext image bits to make the cryptosystem proposed by Huang et al. resistant to chosen-plaintext attack and known-plaintext attack. The modifications in the existing PCS encryption method are proposed to improve its security performance against the potential attacks described above. The Number of Pixel Change Rate (NPCR), Unified Average Changed Intensity (UACI), information entropy, and correlation coefficient analysis are performed to evaluate the statistical performance of the modified PCS method. The simulation analysis reveals that the modified PCS method has better statistical features and is more resistant to attacks than Huang et al.'s PCS method.

• 한국통신학회논문지
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• 제35권12C호
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• pp.977-983
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• 2010

카오스 함수의 출력 값은 예측 불가능하고 무작위처럼 보이며, 이러한 특성은 안전한 암호 시스템에서 요구하는 특성과 일치한다. 이러한 이유로 인해, 카오스 함수를 이용한 암호 시스템이 지금까지 다양하게 제안되어 왔다. 하지만 대부분의 카오스 암호 시스템은 매우 높은 수준의 연산 능력을 필요로 하기 때문에 경량의 시스템에 적용하지 못했다. 본 논문에서는 적은 연산 능력을 가진 시스템에서도 응용 가능한 경량의 카오스 암호 시스템을 제안하고, 제안된 암호 시스템의 연산량 및 안전도와 관련된 성능을 모의 실험을 통하여 제시한다.

• ETRI Journal
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• 제35권3호
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• pp.448-458
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• 2013

This paper presents a generalized post-processing technique for enhancing the pseudorandomness of digital chaotic oscillators through a nonlinear XOR-based operation with rotation and feedback. The technique allows full utilization of the chaotic output as pseudorandom number generators and improves throughput without a significant area penalty. Digital design of a third-order chaotic system with maximum function nonlinearity is presented with verified chaotic dynamics. The proposed post-processing technique eliminates statistical degradation in all output bits, thus maximizing throughput compared to other processing techniques. Furthermore, the technique is applied to several fully digital chaotic oscillators with performance surpassing previously reported systems in the literature. The enhancement in the randomness is further examined in a simple image encryption application resulting in a better security performance. The system is verified through experiment on a Xilinx Virtex 4 FPGA with throughput up to 15.44 Gbit/s and logic utilization less than 0.84% for 32-bit implementations.

• 한국정보처리학회논문지
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• 제3권4호
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• pp.877-882
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• 1996

Bonhoeffer-Van der Pol(BVP)모델을 실제 소자값을 이용하여 하드웨어를 구현하고 A1 coswt를 인가하여 주기 운동과 카오스 운동을 조사하였다. BVP모델의 하드웨어를 구성하기 위해 컴퓨터 시뮬레이션〔11〕에 의해 구현된 결과를 이용하여 실제 소자값 으로 Rescaling 하였으며 각 계수의 값을 a=0.7, b=0.8, c=0.1로 정하고 주기적 자극 전류의 진폭을 0에서 1.3까지 변화시켜 주기운동에서 카오스 운동으로 천이됨을 위 상공간, 시계열 데이터로 확인하였다.

• Ocean and Polar Research
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• 제28권4호
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• pp.459-465
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• 2006

Ambient noise as a background noise in the ocean has been well known for its the various and irregular signal characteristics. Generally, these signals we treated as noise and they are analyzed through stochastical level if they don't include definite sinusoidal signals. This study is to see how ocean ambient noise can be analyzed by the chaotic analysis technique. The chaotic analysis is carried out with underwater ambient noise obtained in areas near the Korean Peninsula. The calculated physical parameters of time series signal are as follows: histogram, self-correlation coefficient, delay time, frequency spectrum, sonogram, return map, embedding dimension, correlation dimension, Lyapunov exponent, etc. We investigate the chaotic pattern of noises from these parameters. From the embedding dimensions of underwater noises, the assesment of underwater noise by chaotic analysis shows similar results if they don't include a definite sinusoidal signal. However, the values of Lyapunov exponent (divergence exponent) are smaller than that of random noise signal. As a result we confirm the possibility of classification of underwater noise using Lyapunov analysis.

• 한국정보통신학회논문지
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• 제7권4호
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• pp.630-637
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• 2003

본 논문에서는 디지털 데이터의 저작권 보호와 무단 복제 방지를 위해 기존의 M-sequence 대신 카오스 시퀀스를 이용한 새로운 워터마킹 방법에 대하여 제안한다. 강인성과 보안성은 워터마킹 처리에 있어 중요한 요소이다. 디지털 영상을 웨이브렛 변환한 후 각 부대역의 계수값들을 인간의 시각 체계를 고려한 다중 임계값으로 분류하고 카오스 시퀀스와 삽입할 워터마크 영상 그리고 랜덤 발생기로 생성된 다중 워터마크 가중치를 이용하여 워터마크 영상을 삽입하였다. 워터마크 검출은 웨이브렛 변환된 각 부대역간의 차신호를 이용하여 검출하였으며 여러가지 가능한 공격에 대해 성능 실험을 하였다. 카오스 시퀀스는 생성하기가 매우 쉬우며, 초기 값에 따라 전혀 다른 시퀀스를 생성하므로 M-sequence에 비해 보안성(security)면에서 더욱 안전하다는 장점을 갖고 있다.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3688-3693
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• 2009

본 논문에서는 두 가지 혼돈맵들 -톱니맵 $S_2(x)$ 와 텐트맵 $T_2(x)-$ 을 연결시킨 하나의 합성맵을 기초로 사용하는 독립된 하나의 합성상태머신을 설계하는 방법 및 그 결과을 제시하였다. 두 가지 다른 혼돈맵들 -톱니맵과 텐트맵- 의 합성 논리를 이용하여 설계된 독립된 하나의 합성상태머신에서 발생하는 혼돈적인 상태들을 그래프적으로 보였으며, 발생하는 의사 난수적인 상태들의 주기는 이산화된 진리표의 정밀도에 따른 길이를 갖는다는 것도 보였다.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2493-2503
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• 2018

Passive dynamic walking exhibits humanoid and energy efficient gaits. However, optimal design of passive walker at multi-variable level is not well studied yet. This paper presents a Chaotic Particle Swarm Optimization (CPSO) algorithm and applies it to the optimal design of flexible passive walker. Hip torsional stiffness and damping were incorporated into flexible biped walker, to imitate passive elastic mechanisms utilized in human locomotion. Hybrid dynamics were developed to model passive walking, and period-one gait was gained. The parameters global searching scopes were gained after investigating the influences of structural parameters on passive gait. CPSO were utilized to optimize the flexible passive walker. To improve the performance of PSO, multi-scroll Jerk chaotic system was used to generate pseudorandom sequences, and chaotic disturbance would be triggered if the swarm is trapped into local optimum. The effectiveness of CPSO is verified by comparisons with standard PSO and two typical chaotic PSO methods. Numerical simulations show that better fitness value of optimal design could be gained by CPSO presented. The proposed CPSO would be useful to design biped robot prototype.

• 대한기계학회논문집A
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• 제29권6호
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• pp.904-912
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• 2005

The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Barrier Embedded Kenics Micromixer (BEKM). In the BEKM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: (i) splitting/reorientation by helical elements inside the microchannel and (ii) stretching/folding via periodically located barriers on the channel wall. The fully three-dimensional geometry of BEKM was realized by a micro-stereolithography technology, in this study, along with a Kenics micromixer and a circular T-pipe. Mixing performances of three micromixers were experimentally characterized in terms of an average mixing color intensity of phenolphthalein. Experimental results show that BEKM has better mixing performance than other two micromixers. Chaotic mixing mechanism, proposed in this study, could be integrated as a mixing component with Micro-Total-Analysis-System, Lab-on-a-chip and so on.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.1180-1200
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• 2017

Currently, automated payment services provide intuitive user interfaces by adapting various wireless communication devices with mobile services. For example, companies like Samsung, Google, and Apple have selected the NFC payment method to service payments of existing credit cards. An electronic payment standard has been released for NFC activation within Korea and will strengthen the safety of payment service communications. However, there are various security risks regarding the NFC-based electronic payment method. In particular, the NFC payment service using the recently released lightweight devices cannot provide the cryptographic strength that is supported by many financial transaction services. This is largely due to its computational complexity and large storage resource requirements. The chaotic map introduced in this study can generate a highly complicated code as it is sensitive to the initial conditions. As the lightweight study using the chaotic map has been actively carried out in recent years, associated authentication techniques of the lightweight environment have been released. If applied with a chaotic map, a high level of cryptographic strength can be achieved that can provide more functions than simple XOR operations or HASH functions. Further, this technique can be used by financial transaction services. This study proposes a mutual authentication technique for NFC-PCM to support an NFC payment service environment based on the chaotic map.