• 한국사이버테러정보전학회:학술대회논문집
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• 한국사이버테러정보전학회 2004년도 제1회 춘계학술발표대회
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• pp.65-70
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• 2004

브로드캐스트 암호화 기법은 공개된 네트워크 상에서 멀티미디어, 소프트웨어, 유료 TV 등의 디지털 정보들을 전송하는데 적용되고 있다. 브로드캐스트 암호화 기법에서 중요한 것은 오직 사전에 허가된 사용자만이 디지털 정보를 얻을 수 있어야 한다는 것이다. 브로드캐스트 메시지가 전송되면 권한이 있는 사용자들은 자신이 사전에 부여받은 개인키를 이용하여 먼저 세션키를 복호화하고 이 세션키를 통하여 디지털 정보를 얻게 된다. 본 논문에서는 브로드캐스트 방법을 이용하여 컨텐츠에 대한 요구사항을 살펴본 뒤 이를 통해 브로드캐스트 암호화의 개념을 적용하여 DRM 모델을 제시하고자 한다. 사용자로 하여금 원하는 복사의 수만큼 복사할 수 있는 권한을 제공함으로써 사용하기에 편리하도록 하였다.

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.476-480
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• 2016

For the application of multiusers, the arrangement and distribution of the keys is a much concerning problem in a cryptosystem. In this paper, we propose an optical encryption scheme with multiple users based on computational ghost imaging (CGI) and orthogonal modulation. The CGI encrypts the secret image into an intensity vector rather than a complex-valued matrix. This will bring convenience for post-processing and transmission of the ciphertext. The orthogonal vectors are taken as the address codes to distinguish users and avoid cross-talk. Only the decryption key and the address code owned by an authorized user are matched, the secret image belonging to him/her could be extracted from the ciphertext. Therefore, there are two security levels in the encryption scheme. The feasibility and property are verified by numerical simulations.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.42-54
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• 2016

A hybrid color and grayscale images encryption scheme based on the quaternion Hartley transform (QHT), the two-dimensional (2D) logistic map, the double random phase encoding (DRPE) in gyrator transform (GT) domain and the three-step phase-shifting interferometry (PSI) is presented. First, we propose a new color image processing tool termed as the quaternion Hartley transform, and we develop an efficient method to calculate the QHT of a quaternion matrix. In the presented encryption scheme, the original color and grayscale images are represented by quaternion algebra and processed holistically in a vector manner using QHT. To enhance the security level, a 2D logistic map-based scrambling technique is designed to permute the complex amplitude, which is formed by the components of the QHT-transformed original images. Subsequently, the scrambled data is encoded by the GT-based DRPE system. For the convenience of storage and transmission, the resulting encrypted signal is recorded as the real-valued interferograms using three-step PSI. The parameters of the scrambling method, the GT orders and the two random phase masks form the keys for decryption of the secret images. Simulation results demonstrate that the proposed scheme has high security level and certain robustness against data loss, noise disturbance and some attacks such as chosen plaintext attack.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권3호
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• pp.1249-1262
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• 2020

Along with the increase of the importance of information used in practice, adversaries tried to take valuable information in diverse ways. The simple and fundamental solution is to encrypt the whole data. Since the cost of encryption is increasing along with the size of data, the cost for securing the data is a burden to a system where the size of the data is not small. For the reason, in some applications where huge data are used for service, service providers do not use any encryption scheme for higher security, which could be a source of trouble. In this work, we introduce a new type of data securing technique named Trapdoor Digital Shredder(TDS) which disintegrates a data to multiple pieces to make it hard to re-construct the original data except the owner of the file who holds some secret keys. The main contribution of the technique is to increase the difficulty in obtaining private information even if an adversary obtains some shredded pieces. To prove the security of our scheme, we first introduce a new security model so called IND-CDA to examine the indistinguishability of shredded pieces. Then, we show that our scheme is secure under IND-CDA model, which implies that an adversary cannot distinguish a subset of shreds of a file from a set of random shreds.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권9호
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• pp.4271-4294
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• 2018

Communication cost is the most important factor in Wireless Sensor Networks (WSNs), as exchanging control keying messages consumes a large amount of energy from the constituent sensor nodes. Time-based Dynamic Keying and En-Route Filtering (TICK) can reduce the communication costs by utilizing local time values of the en-route nodes to generate one-time dynamic keys that are used to encrypt reports in a manner that further avoids the regular keying or re-keying of messages. Although TICK is more energy efficient, it employs no re-encryption operation strategy that cannot determine whether a healthy report might be considered as malicious if the clock drift between the source node and the forwarding node is too large. Secure SOurce-BAsed Loose Synchronization (SOBAS) employs a selective encryption en-route in which fixed nodes are selected to re-encrypt the data. Therefore, the selection of encryption nodes is non-adaptive, and the dynamic network conditions (i.e., The residual energy of en-route nodes, hop count, and false positive rate) are also not focused in SOBAS. We propose an energy efficient selection of re-encryption nodes based on fuzzy logic. Simulation results indicate that the proposed method achieves better energy conservation at the en-route nodes along the path when compared to TICK and SOBAS.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.341-357
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• 2016

A novel asymmetric multiple-image encryption method using an octonion Fresnel transform (OFST) and a two-dimensional Sine Logistic modulation map (2D-SLMM) is presented. First, a new multiple-image information processing tool termed the octonion Fresneltransform is proposed, and then an efficient method to calculate the OFST of an octonion matrix is developed. Subsequently this tool is applied to process multiple plaintext images, which are represented by octonion algebra, holistically in a vector manner. The complex amplitude, formed from the components of the OFST-transformed original images and modulated by a random phase mask (RPM), is used to derive the ciphertext image by employing an amplitude- and phase-truncation approach in the Fresnel domain. To avoid sending whole RPMs to the receiver side for decryption, a random phase mask generation method based on SLMM, in which only the initial parameters of the chaotic function are needed to generate the RPMs, is designed. To enhance security, the ciphertext and two decryption keys produced in the encryption procedure are permuted by the proposed SLMM-based scrambling method. Numerical simulations have been carried out to demonstrate the proposed scheme's validity, high security, and high resistance to various attacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4508-4530
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• 2021

Today distributed data storage service are being widely used. However lack of proper means of security makes the user data vulnerable. In this work, we propose a Randomized Block Size (RBS) model for secure data storage in distributed environments. The model work with multifold block sizes encrypted with the Chinese Remainder Theorem-based RSA (C-RSA) technique for end-to-end security of multimedia data. The proposed RBS model has a key generation phase (KGP) for constructing asymmetric keys, and a rand generation phase (RGP) for applying optimal asymmetric encryption padding (OAEP) to the original message. The experimental results obtained with text and image files show that the post encryption file size is not much affected, and data is efficiently encrypted while storing at the distributed storage server (DSS). The parameters such as ciphertext size, encryption time, and throughput have been considered for performance evaluation, whereas statistical analysis like similarity measurement, correlation coefficient, histogram, and entropy analysis uses to check image pixels deviation. The number of pixels change rate (NPCR) and unified averaged changed intensity (UACI) were used to check the strength of the proposed encryption technique. The proposed model is robust with high resilience against eavesdropping, insider attack, and chosen-plaintext attack.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권6호
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• pp.1619-1637
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• 2024

In today's highly digitized landscape, securing digital communication is paramount due to threats like hacking, unauthorized data access, and network policy violations. The response to these challenges has been the development of cryptography applications, though many existing techniques face issues of complexity, efficiency, and limitations. Notably, sophisticated intruders can easily discern encrypted data during transmission, casting doubt on overall security. In contrast to encryption, steganography offers the unique advantage of concealing data without easy detection, although it, too, grapples with challenges. The primary hurdles in image steganography revolve around the quality and payload capacity of the cover image, which are persistently compromised. This article introduces a pioneering approach that integrates image steganography and encryption, presenting the BitPatternStego method. This novel technique addresses prevalent issues in image steganography, such as stego-image quality and payload, by concealing secret data within image pixels with identical bit patterns as their characters. Consequently, concerns regarding the quality and payload capacity of steganographic images become obsolete. Moreover, the BitPatternStego method boasts the capability to generate millions of keys for the same secret message, offering a robust and versatile solution to the evolving landscape of digital security challenges.

• 정보보호학회논문지
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• 제26권1호
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• pp.17-30
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• 2016

본 논문에서는 효율적인 공개키 기반 공모자 추적 및 제외 스킴을 제안하고자 한다. 공모자 추적 및 제외 스킴은 암호 전송 스킴(Broadcast encryption scheme)에 공모자 추적과 제외 기능을 추가한 것으로 악의적인 사용자들이 유출한 개인키 또는 공모한 해적판 키를 시스템에서 제외함으로서 스킴의 안전성을 유지하는 것이다. 또한 제외 기능은 일부 사용자만을 위한 암호문을 만들 수 있어 다양한 응용 환경에 적용할 수 있는 스킴이다. 본 논문에서는 합성수 위수의 겹선형 군을 기반으로 설계된 스킴[Augmented broadcast encryption scheme]을 소수 위수의 겹선형 군을 기반으로 하는 스킴으로 변화시켰고, 효율성의 척도인 공개키, 개인키, 암호문의 크기를 크게 개선했다. 또한 제외 기능에 대한 분석을 통해 기존 논문의 제한적인 제외 기능을 충분한 제외 기능으로 확장하는 결과를 얻을 수 있었다. 본 논문에서 제안하는 스킴의 구조는 계층적 구조 또는 피라미드 구조를 갖는 우리나라 정부, 군 조직 등에 쉽게 적용 가능하다.

• 융합보안논문지
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• 제12권4호
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• pp.85-90
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• 2012

DES는 64비트 단위로 나뉘어 진 각각의 블록이 한번의 암호화 알고리즘을 거쳐 암호화 된다. 대칭알고리즘으로서 똑같은 키와 알고리즘이 암호화와 복호화에 쓰인다. 복호화 할 때 키를 반대로 적용하는 등의 약간의 차이는 있다. 키 길이는 64비트로 표현되는데 이 중에서 실제로는 56비트만이 키로서 사용되고 나머지 8비트는 패리티 체크 비트로 사용된다. 암호화는 64비트 블록과 56비트 키를 바탕으로 만든 16개의 보조키가 총 16번의 혼돈과 확산을 거쳐 완료된다. DES 알고리즘을 선택한 이유는 암호 강도에 대한 의문이 제기되고 있기는 하지만 상업적으로 가장 널리 보급되어 이용되고 있다. 또한 기본 알고리즘을 DES로 채택한 현장에서 앞으로도 상당한 기간 동안 이용이 계속될 것으로 예상되는 DES 알고리즘을 효과적으로 활용하는 방안이 현장에서 참고되기를 기대한다.