• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.3
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• pp.541-547
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• 2019

As leakage cases of personal information increase, the concern of personal information protection is also increasing. As a result, most applications encrypt and store sensitive information such as personal information. Especially, in case of instant messengers, it is more difficult to find database where is not encrypted and stored. However, this kind of database encryption acts as anti-forensic from the point of view of digital forensic investigation. In this paper, we analyze database encryption process of MalangMalang Talkcafe application which is one of instant messenger. Based on our analysis, we propose a decryption method and explain the meaningful information collected in the database.

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.202-205
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• 2003

무한 복제가 가능한 디지털 컨텐츠의 보호를 위해 사용한 암호화 기술은 최종 사용자의 환경에 컨텐츠의 복호화를 위한 모든 키가 존재해야 한다는 전제를 달고 있다는 점과, 사용자의 클라이언트 환경이 다양한 악의적인 공격에 노출되어 있다는 점은 디지털 컨텐츠의 유통에서 클라이언트 환경의 설계가 매우 중요하다는 것을 말해준다. 본 논문에서는 라이센스 기반의 디지털 컨텐츠 유통 시스템을 위한 DRM 클라이언트를 설계한다. 여기서 설계된 DRM 클라이언트는 사용자에게 노출되어서는 안되는 복호화 키를 비롯한 중요한 정보들을 저장하는 시큐어 데이터 영역, 컨텐츠를 활용하기 위한 뷰어 프로그램을 DRM 정책에 따라 제어하기 위한 플러그인 구조, 라이센스와 암호화된 컨텐츠에 담긴 정보를 바탕으로 DRM정책을 결정하고 이에 따라 클라이언트를 구성하는 각 모듈을 제어하는 DRM 제어부, 암호화된 컨텐츠를 복호화하여 넘겨주는 필터 드라이버로 나뉘어 있으며 이를 구현하기 위한 기술과 함께 소개한다.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.249-254
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• 2003

In this paper, we propose an improved image encryption and decryption method using a phase-encoded virtual image and interference. An original image is simply decrypted by interfering a reference wave with the wave passing through a decrypting key and the encrypted image, where every image has grey level. The proposed encryption is performed by the multiplication of an encrypting key and a phase-encoded virtual image which dose not contain any information for the original image. Therefore even if unauthorized people analyze the encrypted image, they cannot reconstruct the original image. Also grey image encryption can improve the encryption level compared to binary image encryption. Computer simulation and optical experiments confirmed that the proposed technique is a simple for optical encryption.

• Convergence Security Journal
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• v.22 no.3
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• pp.33-39
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• 2022

Recently, cyberattacks on infrastructure have been continuously occurring with the starting of neutralizing the user authentication function of information systems. Accordingly, the vulnerabilities of system are increasing day by day, such as the increase in the vulnerabilities of the encryption system. In this paper, an alternative technique for the symmetric key algorithm has been developed in order to build the encryption algorithm that is not easy for beginners to understand and apply. Vigenere Cipher is a method of encrypting alphabetic text and it uses a simple form of polyalphabetic substitution. The encryption application system proposed in this study uses the simple form of polyalphabetic substitution method to present an application model that integrates the three steps of encryption table creation, encryption and decryption as a framework. The encryption of the original text is done using the Vigenère square or Vigenère table. When applying to the automatic generation of secret keys on the information system this model is expected that integrated authentication work, and analysis will be possible on target system. ubstitution alphabets[3].

• Journal of IKEEE
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• v.28 no.3
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• pp.271-278
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• 2024

An encryption and decryption method using phase mapping of a gray scale image based on a phase-shifting interferometry principle is proposed in which an encrypted image is formed into complex digital hologram function by symmetric security key in the proposed encryption system.. The gray scale image to be encrypted is converted to phase mapped function that is mixed with a randomly generated binary security encryption key and is used as an input. Decryption of phase information is performed by complex digital hologram and security encryption key, which reconstructs the original gray scale image by phase unmapping. The proposed method confirms that correlation coefficient of the decrypted image is 0.995 when quantization level of CCD is 8-bits(2⁸=256 levels).

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.231-239
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• 2006

In recent years, a hierarchical security architecture has been widely studied because it can efficiently protect information by allowing an authorized user access to the level of information. However, the conventional hierarchical decryption methods require several decryption keys for the high level information. In this paper, we propose a hierarchical image encryption using random phase masks and Walsh code having orthogonal characteristics. To decrypt the hierarchical level images by only one decryption key, we combine Walsh code into the hierarchical level system. For encryption process, we first perform a Fourier transform for the multiplication results of the original image and the random phase mask, and then expand the transformed pattern to be the same size and shape of Walsh code. The expanded pattern is finally encrypted by multiplying with the Walsh code image and the binary phase mask. We generate several encryption images as the same encryption process. The reconstruction image is detected on a CCD plane by a despread process and Fourier transform for the multiplication result of encryption image and hierarchical decryption keys which are generated by Walsh code and binary random phase image. Computer simulations demonstrate that the proposed technique can decrypt hierarchical information by using only one level decryption key image and it has a good robustness to the data loss such as random cropping.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.2
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• pp.33-40
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• 2016

Due to the growth of social network systems (SNS), big data are realized and Hadoop was developed as a distributed platform for analyzing big data. Enterprises analyze data containing users' sensitive information by using Hadoop and utilize them for marketing. Therefore, researches on data encryption have been done to protect the leakage of sensitive data stored in Hadoop. However, the existing researches support only the AES encryption algorithm, the international standard of data encryption. Meanwhile, Korean government choose ARIA algorithm as a standard data encryption one. In this paper, we propose a HDFS data encryption scheme using ARIA algorithms on Hadoop. First, the proposed scheme provide a HDFS block splitting component which performs ARIA encryption and decryption under the distributed computing environment of Hadoop. Second, the proposed scheme also provide a variable-length data processing component which performs encryption and decryption by adding dummy data, in case when the last block of data does not contains 128 bit data. Finally, we show from performance analysis that our proposed scheme can be effectively used for both text string processing applications and science data analysis applications.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06b
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• pp.355-360
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• 2008

대부분의 임베디드 시스템들은 유선 및 무선 네트워크에 연결되어 있으며 이들이 생성하는 데이터는 개인, 기관, 또는 국가에 상당히 중요한 정보일 수 있다. 따라서 통신 시 보안에 대한 요구는 향후 더욱 크게 증가할 것으로 전망된다. 임베디드 시스템에서의 또 다른 중요한 요구사항 중의 하나는 저전력 특성이다. 따라서 중요 데이터의 안전한 전송을 위한 암호화 및 복호화 그리고 네트워크 프로토콜 스택의 수행에 따른 전력 사용량 정보는 차세대 저전력 임베디드 시스템을 설계 및 개발하기 위해서 필수적으로 요구될 것이다. 하지만 기존 연구들은 단편적인 전력 사용량만을 분석하고 있다. 본 논문은 보안 데이터를 위한 암호화, 복호화, 그리고 데이터 송수신을 위한 네트워크 프로토콜 스택의 수행에 걸리는 전력 사용량과 오버헤드를 함께 측정하고 분석한다. 측정 결과 3DES 기반의 암호화 및 복호화 작업 동안의 전력 사용량이 TCP/IP 통신을 위한 전력 사용량 보다 데이터 크기가 증가함에 따라 더욱 크게 측정되었다. 해당 작업의 수행 오버헤드 역시 유사한 성향을 보였다. 그리고 프로세서 코어의 전력 사용량은 시스템 전체 사용량의 $10{\sim}22%$ 정도를 차지하는 것으로 측정되었다. 이러한 연구 결과는 임베디드 시스템에서 저전력 보안 데이터 전송을 위해 고려할 사항들을 정량적으로 제시하여 해당 연구 분야에 기여할 수 있다.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.507-513
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• 2006

In this paper, we propose an improved image encryption and fault-tolerance decryption method using phase wrapping and phase encoding in the frequency domain. To generate an encrypted image, an encrypting key which denotes the product of a phase-encoded virtual image, not an original image, and a random phase image is zero-padded and Fourier transformed and its real-valued data is phase-encoded. The decryption process is simply performed by performing the inverse Fourier transform for multiplication of the encrypted key with the decrypting key, made of the proposed phase wrapping method, in the output plane with a spatial filter. This process has the advantages of solving optical alignment and pixel-to-pixel mapping problems. The proposed method using the virtual image, which does not contain any information from the original image, prevents the possibility of counterfeiting from unauthorized people and also can be used as a current spatial light modulator technology by phase encoding of the real-valued data. Computer simulations show the validity of the encryption scheme and the robustness to noise of the encrypted key or the decryption key in the proposed technique.

• The Journal of the Korea Contents Association
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• v.6 no.11
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• pp.1-7
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• 2006

In this paper, a SOAP based ebXML cryptography system is proposed for the optimum XML document encryption using RSA algorithm in e-Marketplace. And ciphering algorithms of DES, 3DES, RSA, and proposed RSA were used for the performance analysis of ebXML cryptography system. The network performance of ciphering and deciphering times is evaluated for its enhancement of SOAP based ebXML ciphering e-Marketplace systems using the same block and document sizes by computer simulations.