• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.588-596
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• 2008

For the patients' privacy, secure access control of medical images is essentially necessary. In this paper, two types of Region of Interest (ROI)-based selective encryption schemes are proposed, which concentrate on the security of crucial parts in medical images. The first scheme randomly inverts the most significant bits of ROI coefficients in several high frequency subbands in the transform domain, which only incurs little loss on compression efficiency. The second scheme employs a symmetric key encryption to encrypt selectively the ROI data in the final code-stream, which provides sufficient confidentiality. Both of two schemes are backward compatible so as to ensure a standard bitstream compliant decoder so the encrypted images can be reconstructed without any crash.

• The KIPS Transactions:PartC
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• v.8C no.5
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• pp.525-534
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• 2001

Generally, compression and encryption procedures are performed independently in lossless image compression and encryption. When compression is followed by encryption, the compressed-stream should have the property of randomness because its entropy is decreased during the compression. However, when full data is compressed using image compression methods and then encrypted by encryption algorithms, real-time processing is unrealistic due to the time delay involved. In this paper, we propose to combine compression and encryption to reduce the overall processing time. It is method decomposing gray-scale image by means of quadtree compression algorithms and encrypting the structural part. Moreover, the lossless compression ratio can be increased using a transform that provides an decorrelated image and homogeneous region, and the encryption security can be improved using a reconstruction of the unencrypted quadtree data at each level. We confirmed the increased compression ratio, improved encryption security, and real-time processing by using computer simulations.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2574-2576
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• 2004

본 논문에서 디지털 영상의 인증과 무결성을 확인하는 새로운 워터마킹 기법을 제안하였다. 컨텐츠에 대한 인증과 무결성을 체크하는 방법 중, 암호학적 해쉬함수(MD5)를 이용한 Wong의 방법이 인증과 무결성을 위한 워터마크 방법으로는 가장 적합하다. 특히 이 방법은 암호학적인 해쉬함수를 사용하므로 워터마킹 알고리즘의 안정성이 암호학적 해쉬함수의 안정성에 의존하게 되므로 안전하다. 해쉬 값을 계산하려면 법(modulus), 보수 (complement), 시프트 (shift), XOR (bitwise exclusive-or) 등 연산이 필요하다. 그러나 본 논문에서는 곱셈 연산만 필요로 한 산술부호화기법 (Arithmetic coding)을 이용하였다. 이 기법은 입력되는 심벌 (symbol)들의 확률구간을 계속적으로 곱하여 결과적으로 얻어지는 누적확률구간을 출력한다. 본 논문에서 키(key) 값에 의하여 심벌들의 확률구간을 결정하고, 그리고 키 값에 의하여 심벌들의 입력순서론 재배치함으로써 결과적으로 얻어지는 누적확률 값은 키 값에 의존하게 하였다. 실험을 통하여 본 알고리즘이 무결성을 입증할 수 있고, PSNR은 51.13dB 이상으로서 아주 좋으며, 위변조를 판단하는데 소요되는 시간은 해쉬함수 (MD5)를 사용하는데 걸리는 시간이 1/3배이다. 그러므로 실시간으로 사용 가능하다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.4
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• pp.728-736
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• 2007

The more improved the Internet and the information technology, the stronger cryptographic system is required which can satisfy the information security on the platform of personal hand-held devices or smart card system. This paper introduces a case study of designing an elliptic curve cryptographic processor of a high performance that can be suitably used in a wireless communicating device or in an embedded system. To design an efficient cryptographic system, we first analyzed the operation hierarchy of the elliptic curve cryptographic system and then implemented the system by adopting a serial cell multiplier and modified Euclid divider. Simulation result shows that the system was correctly designed and it can compute thousands of operations per a secdond.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.894-904
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• 1999

In this paper, a synchronized stream cryptosystem for secure communication in radio channel is designed and its security level is analyzed. The main parts of the proposed cryptosystem consist of synchronization pattern generator, session key generator, and key stream generator. The system performance is evaluated by analyzing the security level depending on the randomness, period, linear complexity, and correlation immunity. Experimental results with image data signal in the 10-1 and 10-2 channel error environment demonstrate the proper operation of the implemented crypto system.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2007.11a
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• pp.68-68
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• 2007

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.25-32
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• 2010

Recently a passenger ship and liner has been spread throughout men of diversity, the space and informations is not open to general passenger. Therefore security systems are necessary for special sailors to admit them. Although security systems has a variety usage methods which are organism recognition(finger printer, iritis and vein etc) a few years ago, these usages has a defect reusing other objects because of leaving a trace. Therefore this paper designs and implements using 3D Qube image password interface which hand gestures are recognized after acquiring from 2D input image for protective marker of finger printer.

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.114-122
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• 2004

In this paper, we proposed an optical encryption and decryption technique that uses a nail bed pattern as a key-code. Since the technique uses a nail bed pattern that is a biometric signal of an encryptor, the technique is robust about a fake key or illegal use of a key. In addition to this, the encrypted image contains the biometric information of the encryptor. This makes the proposed technique also be applied to authentication.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.6
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• pp.15-26
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• 2001

Visual cryptography is a simple method in which secret information can be directly decoded in human visual system without any cryptographic computations. When the secret image is scattered to n random shares(slides), this scheme has some week point such as pixel expansion and contrast degradation. Therefore, it is necessary to reduce the pixel expansion and improve the contrast in recovered image. In this paper, we propose a new construction method for (k, n) visual cryptography using the cumulative matrix. In case k is odd, we can construct the cumulative matrix perfectly. For even k, the contrast of special pair in decoded image can be achieved best by permitting multiple contract. The proposed method is more simple than that of S. Droste\`s in construction and the average contrast of decoded image is improved for the most part. Also, we show that the basis matrices depending on the cumulative matrix are able to be applied for the general access structure.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1992.06a
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• pp.490-494
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• 1992