• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.6116-6132
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• 2017

The proxy re-encryption allows an intermediate proxy to convert a ciphertext for Alice into a ciphertext for Bob without seeing the original message and leaking out relevant information. Unlike many prior identity based proxy re-encryption schemes which are based on the number theoretic assumptions such as large integer factorization and discrete logarithm problem. In this paper, we first propose a novel identity based proxy re-encryption scheme which is based on the hardness of standard Learning With Error(LWE) problem and is CPA secure in the standard model. This scheme can be reduced to the worst-case lattice hard problem that is able to resist attacks from quantum algorithm. The key step in our construction is that the challenger how to answer the private query under a known trapdoor matrix. Our scheme enjoys properties of the non-interactivity, unidirectionality, anonymous and so on. In this paper, we utilize primitives include G-trapdoor for lattice and sample algorithms to realize simple and efficient re-encryption.

• 디지털산업정보학회논문지
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• 제12권2호
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• pp.41-49
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• 2016

Lossless encryption methods are more applicable than lossy encryption methods when marginal distortion is not tolerable. In this research, the author propose a novel lossless symmetric key encryption/decryption technique. In the proposed algorithm, the image is transformed into the frequency domain using the lifting wavelet transform, then the image sub-bands are encrypted in a such way that guarantees a secure, reliable, and an unbreakable form. The encryption involves scattering the distinguishable frequency data in the image using a reversible weighting factor amongst the rest of the frequencies. The algorithm is designed to shuffle and reverse the sign of each frequency in the transformed image before the image frequencies are transformed back to the pixel domain. The results show a total deviation in pixel values between the original and encrypted image. The decryption algorithm reverses the encryption process and restores the image to its original form. The proposed algorithm is evaluated using standard security and statistical methods; results show that the proposed work is resistant to most known attacks and more secure than other algorithms in the cryptography domain.

• 스마트미디어저널
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• 제4권4호
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• pp.39-46
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• 2015

본 논문은 사물인터넷 보안용 경량 암호 알고리듬 중, '128비트 블록 암호 LEA'의 암호화 블록 하드웨어 구현에 대해 기술한다. 라운드 함수 블록과 키 스케줄 블록은 높은 처리성능을 위하여 병렬회로로 설계되었다. 암호화 블록은 128비트의 비밀키를 지원하며, FSM 방식과 24/n단계(n = 1, 2, 3, 4, 8, 12) 파이프라인 방식으로 설계되었다. LEA-128 암호화 블록을 Verilog-HDL로 모델링하여 FPGA 상에서 구현하고, 합성결과로부터 최소면적 및 최대처리성능을 제시한다.

• Journal of the Korean Data and Information Science Society
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• 제25권6호
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• pp.1419-1429
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• 2014

본 논문에서는 1977년 미국 국립기술표준원이 FIPS (연방정보처리기준; federal information processing standard) 46으로 공표한 암호화 표준인 현대 대칭키 블록 암호 DES (data encryption standard)의 암호화 전 과정에 대하여 엑셀 매크로 기능을 활용하여 암호화와 복호화에 사용할 수 있는 매크로를 개발하였다. 평문과 암호문과의 관계를 숨기는 확산과 암호문과 암호 키 사이의 관계를 숨기는 혼돈을 반복하는 라운드는 DES 구조의 핵심이다. 평문을 암호화 하는 DES 구조를 살펴보고 엑셀 매크로기능을 이용하여 암호화를 완성하는 매크로의 구현을 제안하고 개발된 매크로의 정확성과 활용성을 서술하였다.

• 디지털산업정보학회논문지
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• 제14권2호
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• pp.49-59
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• 2018

Encryption of digital images has been requested various fields. In the meantime, many algorithms based on a text - based encryption algorithm have been proposed. In this paper, we propose a method of encryption in wavelet transform domain to utilize the characteristics of digital image. In particular, wavelet transform is used to reduce the association between the encrypted image and the original image. Wavelet packet transformations can be decomposed into more subband images than wavelet transform, and various position permutation, numerical transformation, and visual transformation are performed on the coefficients of this subband image. As a result, this paper proposes a method that satisfies the characteristics of high encryption strength than the conventional wavelet transform and reversibility. This method also satisfies the lossless symmetric key encryption and decryption algorithm. The performance of the proposed method is confirmed by visual and quantitative. Experimental results show that the visually encrypted image is seen as a completely different signal from the original image. We also confirmed that the proposed method shows lower values of cross correlation than conventional wavelet transform. And PSNR has a sufficiently high value in terms of decoding performance of the proposed method. In this paper, we also proposed that the degree of correlation of the encrypted image can be controlled by adjusting the number of wavelet transform steps according to the characteristics of the image.

• 한국항행학회논문지
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• 제20권1호
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• pp.72-78
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• 2016

리눅스는 초창기부터 사용자 패스워드의 암호화를 위해 해시 알고리즘인 MD-5를 사용해 왔다. 최근 보안성이 강화된 패스워드 관리가 요구되면서 엔터프라이즈 리눅스 시스템에서는 MD-5보다 더욱 높은 신뢰성을 보이는 SHA-512 알고리즘을 사용하고 있다. 본 논문에서는 해시 및 암호화 알고리즘의 특징에 대해 비교 분석하고, 리눅스 사용자 정보의 관리 체제에 대해 알아본다. 이러한 분석을 기반으로 사용자 패스워드에 적용된 해시 알고리즘의 보안성에 대해 분석하고, 추가적으로 Apache, PHP, MySQL과 같은 공개 소프트웨어 파일 검증에 사용되는 해시 알고리즘 적용 사례를 분석한다. 마지막으로 관련 보안 도구인 John The Ripper를 분석하여 사용자 패스워드 관리를 통한 시스템 보안 강화 방법을 제시한다.

• International Journal of Computer Science & Network Security
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• 제22권6호
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• pp.310-318
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• 2022

Job offers have become more widespread and it has become easier and faster to apply for jobs through electronic recruitment platforms. In order to increase the protection of the data that is attached to the recruitment platforms. In this research, a proposed model was created through the use of hybrid encryption, which is used through the following algorithms: AES,Twofish,. This proposed model proved the effectiveness of using hybrid encryption in protecting personal data.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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• pp.940-943
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• 2002

This paper presents hardware implementations of the two representative cryptographic algorithms, Advanced Encryption Standard (Rijndael), and the present American federal standard (Triple DES) using a PCI- based FPGA board named "EBSW-1" This board bases on a FPGA chip (Xilinx Virtex300 XCV300PQ240-4). The implementation results of these two algorithms were tested successfully. AES circuit could proceed an encryption as well as a decryption two times faster than the Triple-DES circuit, while the former circuit used higher rates of CLBs. Besides, if these architectures use pipeline-registers, the processing speed will be increased about 1.5 times than the presented circuits.

• 한국멀티미디어학회논문지
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• 제9권10호
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• pp.1371-1379
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• 2006

본 논문에서는 여러 문자열 단위로 입력되는 문자열을 하나의 문자열로 구성하기 위하여 문자열 길이 정보를 이용한 패딩 알고리즘을 제안한다. 기존의 패딩 알고리즘은 단순히 공백 문자를 삽입함으로써 실제 문자열과 패딩 문자를 구분하지 못하는 문제점을 가지고 있다. 이러한 문제점을 해결하기 위하여 본 논문에서는 패딩하는 문자열 길이를 패딩 값으로 구성한다. 이렇게 함으로써 단순히 공백 문자나 '00'을 패딩하는 경우보다 문자열과 패딩 문자를 구분하는 것이 훨씬 용이하고, 정확히 동작된다. 본 논문에서 제안하는 패딩 알고리즘은 데이터 암호화 및 복호화 알고리즘에 사용가능하다.

• International Journal of Computer Science & Network Security
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• 제22권6호
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• pp.75-82
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• 2022

Medical data is one of the data that must be kept in safe containers, far from intrusion, viewing and modification. With the technological developments in hospital systems and the use of cloud computing, it has become necessary to save, encrypt and even hide data from the eyes of attackers. Medical data includes medical images, whether they are x-ray images of patients or others, or even documents that have been saved in the image format. In this review, we review the latest research and the latest tools and algorithms that are used to protect, encrypt and hide these images, and discuss the most important challenges facing these areas.