• 한국수학교육학회지시리즈B:순수및응용수학
• /
• 제12권2호
• /
• pp.143-152
• /
• 2005

We present a new block cipher called DyC. It consists of four sets (procedures) having the different $2^2,\;2^2,\;2^4$, and $2^8$ one-to-one correspondence functions as the elements. The round key is used to determine exactly one composite function from the possible $2^{16}$ composite functions. DyC supports 8 $\times$ n bit key size, 16 $\times$ m bit block length, and n rounds. We have confirmed that DyC offers security against other well-known advanced cryptanalytic attacks including the slide attacks and interpolation attacks. In this paper, we show several properties of the key schedule of DyC by mathematical analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권11호
• /
• pp.5717-5730
• /
• 2019

LBlock-s is the core block cipher of authentication encryption algorithm LAC, which uses the same structure of LBlock and an improved key schedule algorithm with better diffusion property. Using the differential properties of the key schedule algorithm and the cryptanalytic technique which combines impossible boomerang attacks with related-key attacks, a 15-round related-key impossible boomerang distinguisher is constructed for the first time. Based on the distinguisher, an attack on 22-round LBlock-s is proposed by adding 4 rounds on the top and 3 rounds at the bottom. The time complexity is about only 2^68.76 22-round encryptions and the data complexity is about 2⁵⁸ chosen plaintexts. Compared with published cryptanalysis results on LBlock-s, there has been a sharp decrease in time complexity and an ideal data complexity.

• Journal of Platform Technology
• /
• 제11권1호
• /
• pp.72-84
• /
• 2023

With the rise of the Internet of Things, the security of such lightweight computing environments has become a hot topic. Lightweight block ciphers that can provide efficient performance and security by having a relatively simpler structure and smaller key and block sizes are drawing attention. Due to these characteristics, they can become a target for new attack techniques. One of the new cryptanalytic attacks that have been attracting interest is Neural cryptanalysis, which is a cryptanalytic technique based on neural networks. It showed interesting results with better results than the conventional cryptanalysis method without a great amount of time and cryptographic knowledge. The first work that showed good results was carried out by Aron Gohr in CRYPTO'19, the attack was conducted on the lightweight block cipher SPECK-/32/64 and showed better results than conventional differential cryptanalysis. In this paper, we first apply the Differential Neural Distinguisher proposed by Aron Gohr to the block ciphers HIGHT and GOST to test the applicability of the attack to ciphers with different structures. The performance of the Differential Neural Distinguisher is then analyzed by replacing the neural network attack model with five different models (Multi-Layer Perceptron, AlexNet, ResNext, SE-ResNet, SE-ResNext). We then propose a Related-key Neural Distinguisher and apply it to the SPECK-/32/64, HIGHT, and GOST block ciphers. The proposed Related-key Neural Distinguisher was constructed using the relationship between keys, and this made it possible to distinguish more rounds than the differential distinguisher.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제17권12호
• /
• pp.3398-3415
• /
• 2023

Internet-of-Things (IoT) is an emerging technology that interconnects millions of small devices to enable communication between the devices. It is heavily deployed across small scale to large scale industries because of its wide range of applications. These devices are very capable of transferring data over the internet including critical data in few applications. Such data is exposed to various security threats and thereby raises privacy-related concerns. Even devices can be compromised by the attacker. Modern cryptographic algorithms running on traditional machines provide authentication, confidentiality, integrity, and non-repudiation in an easy manner. IoT devices have numerous constraints related to memory, storage, processors, operating systems and power. Researchers have proposed several hardware and software implementations for addressing security attacks in lightweight encryption mechanism. Several works have made on lightweight block ciphers for improving the confidentiality by means of providing security level against cryptanalysis techniques. With the advances in the cipher breaking techniques, it is important to increase the security level to much higher. This paper, focuses on securing the critical data that is being transmitted over the internet by PRESENT using key-based dynamic S-Box. Security analysis of the proposed algorithm against other lightweight block cipher shows a significant improvement against linear and differential attacks, biclique attack and avalanche effect. A novel key-based dynamic S-Box approach for PRESENT strongly withstands cryptanalytic attacks in the IoT Network.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권6호
• /
• pp.2148-2167
• /
• 2021

The proliferation of the Internet of Things (IoT) technologies and applications, especially the rapid rise in the use of mobile devices, from individuals to organizations, has led to the fundamental role of secure wireless networks in all aspects of services that presented with many opportunities and challenges. To ensure the CIA (confidentiality, integrity and accessibility) security model of the networks security and high efficiency of performance results in various resource-constrained applications and environments of the IoT platform, DDO-(data-driven operation) based constructions have been introduced as a primitive design that meet the demand of high speed encryption systems. Among of them, the TMN-family ciphers which were proposed by Tuan P.M., Do Thi B., etc., in 2016, are entirely suitable approaches for various communication applications of wireless mobile networks (WMNs) and advanced wireless sensor networks (WSNs) with high flexibility, applicability and mobility shown in two different algorithm selections, TMN64 and TMN128. The two ciphers provide strong security against known cryptanalysis, such as linear attacks and differential attacks. In this study, we demonstrate new probability results on the security of the two TMN construction versions - TMN64 and TMN128, by proposing efficient related-key recovery attacks. The high probability characteristics (DCs) are constructed under the related-key differential properties on a full number of function rounds of TMN64 and TMN128, as 10-rounds and 12-rounds, respectively. Hence, the amplified boomerang attacks can be applied to break these two ciphers with appropriate complexity of data and time consumptions. The work is expected to be extended and improved with the latest BCT technique for better cryptanalytic results in further research.

• 한국항행학회논문지
• /
• 제19권1호
• /
• pp.48-52
• /
• 2015

본 논문에서는 2011년에 제안된 암호와 복호가 동일한 블록 암호 SSB에 대한 차분 오류 공격을 제안한다. 이 알고리즘은 국제표준 블록암호를 기반으로 설계된 블록 암호로써 하드웨어 구현에서 장점을 갖게 설계되었다. 차분 오류 공격은 부채널 공격 기법 중 하나로 오류 주입 공격과 차분 공격을 결합한 것이다. SSB는 하드웨어 환경에 적합한 알고리즘이므로 차분 오류 공격에 대해 안전성을 가져야 한다. 그러나 본 논문에서 제안하는 차분 오류 공격을 이용하면, 1 개의 랜덤 바이트 오류를 주입과 $2^8$의 전수조사를 통해 SSB의 128 비트 비밀키를 복구할 수 있다. 이 결과는 암호와 복호가 동일한 블록 암호 SSB의 안전성을 분석한 첫 번째 결과이다.

• Journal of Computing Science and Engineering
• /
• 제8권4호
• /
• pp.187-198
• /
• 2014

In this paper an efficient image encryption scheme based on cyclic rotations and multiple blockwise diffusions with two chaotic maps is proposed. A Sin map is used to generate round keys for the encryption/decryption process. A Pomeau-Manneville map is used to generate chaotic values for permutation, pixel value rotation and diffusion operations. The encryption scheme is composed of three stages: permutation, pixel value rotation and diffusion. The permutation stage performs four operations on the image: row shuffling, column shuffling, cyclic rotation of all the rows and cyclic rotation of all the columns. This stage reduces the correlation significantly among neighboring pixels. The second stage performs circular rotation of pixel values twice by scanning the image horizontally and vertically. The amount of rotation is based on $M{\times}N$ chaotic values. The last stage performs the diffusion four times by scanning the image in four different ways: block of $8{\times}8$ pixels, block of $16{\times}16$ pixels, principal diagonally, and secondary diagonally. Each of the above four diffusions performs the diffusion in two directions (forwards and backwards) with two previously diffused pixels and two chaotic values. This stage makes the scheme resistant to differential attacks. The security and performance of the proposed method is analyzed systematically by using the key space, entropy, statistical, differential and performance analysis. The experimental results confirm that the proposed method is computationally efficient with high security.

• 정보보호학회논문지
• /
• 제24권6호
• /
• pp.1091-1102
• /
• 2014

전력 분석 공격은 물리적 장치에 내장된 암호 알고리듬을 수행할 때 발생하는 부채널 전력 정보를 이용하여 사용자의 비밀 키를 찾아내는 공격 기법이다. 특히, RSA와 같은 공개 키 암호 시스템에 사용되는 멱승은 수백 번의 모듈라 곱셈으로 이루어져 있는데 이 연산이 전력 분석 공격의 목표가 되어 왔다. 최근에는 동일한 입력을 가지는 두 개의 모듈라 곱셈에서 발생한 전력의 상관 분석을 통해 비밀 키를 추출하는 공격이 제안되었다. 본 논문에서는 모듈라 곱셈의 입력충돌에 기반한 부채널 공격의 원리를 살펴보고 정규화 특성을 갖는 멱승 알고리듬에 대한 취약성을 분석하였다. 또한, 충돌 입력쌍을 이용한 상관 전력 분석 공격을 포함한 기존 부채널 공격에 대응할 수 있는 효율적인 멱승 방법을 제안하고 안전성을 비교 분석하였다.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
• /
• 제4권3호
• /
• pp.105-108
• /
• 2015

본 논문에서는 2011년에 제안된 비트 슬라이스 대합 S-박스에 의한 대칭 SPN 블록 암호에 대한 차분 오류 공격을 제안한다. 이 블록 암호는 AES를 기반으로 설계되었으며, 암호화와 복호화를 동일하게 구성하여 제한적 하드웨어 및 소프트웨어 환경에서 장점을 가지도록 설계되었으므로, 이 블록 암호는 부채널 분석에 대한 안전성을 가져야 한다. 그러나 본 논문에서 제안하는 공격 방법은 1개의 랜덤 바이트 오류 주입과 $2^8$번의 전수 조사를 통해 본 블록 암호의 128-비트 비밀키를 복구한다. 이 분석 결과는 본 블록 암호에 대한 첫 번째 결과이다.

• 정보보호학회논문지
• /
• 제1권1호
• /
• pp.16-28
• /
• 1991

Knapsack 암호체계는 NP-Complete 인 Knapsack 문제에 기초한 공개키 암호체계이다. 이러한 암호체계의 안정성에 관하여서는 그동안 많은 논란이 있어 왔다. 쉬운 Knapsack 문제를 모듈라연산으로 숨기는 거의 모든Knapsack 암호체계가 계속하여 개발되어 왔다.특히 Bose-Chowla 정리에 근거하여 모듈라 연산을 사용하지 않는 Chor_Rivest knapsack 암호체계는 기존의 모든 암호분석 방법에 대하여 안전한 것으로 알려져 있다. 본 연구에서는 Knapsack 문제를 정수계획법 문제로 변환하고 이를 이완하여 해를 구함으로써 Knapsack 문제의 부분해를 구할 수 있음을 보인다. 이는 일반적인 Knapsack 암호체계는 구현상의 효율성이 제고된 안전한 Knapsack 공개키 암호체계를 제시하고자 한다.