• Journal of Korea Multimedia Society
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• v.4 no.2
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• pp.136-144
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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. This scheme is a kind of secret sharing scheme in which secret of image type is distributed to n random image(we call it share). When the secret image is distributed to n shares, the original pixel is expanded as much as the size of column in basis matrix. It causes the deterioration of contrast in docoded secret image. Therefore, many researches have performed to reduce the size of pixel expansion and to improve the contrast by overlapping the row in basis matrix for (k, n) visual cryptography. In addition, we show that the proposed method can construct the (k, n) visual cryptography with multiple contrasts depending on selecting k out of n slides in a group.

• Journal of Korea Multimedia Society
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• v.20 no.12
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• pp.1913-1927
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• 2017

Encryption technology is to hide information in a cyberspace built using a computer and to prevent third parties from changing it. If a malicious user accesses unauthorized device or application services on the Internet of objects, it may be exposed to various security threats such as data leakage, denial of service, and privacy violation. One way to deal with these security threats is to encrypt and deliver the data generated by a user. Encrypting data must be referred to a technique of changing data using a complicated algorithm so that no one else knows the content except for those with special knowledge. As computers process computations that can be done at a very high speed, current cryptographic techniques are vulnerable to future computer performance improvements. We designed and implemented a new encryption program that combines ancient and modern cryptography so that the user never knows about data management, and transmission. The significance of this paper is that it is the safest method to combine various kinds of encryption methods to secure the weaknesses of the used cryptographic algorithms.

• The Journal of the Korea Contents Association
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• v.1 no.1
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• pp.74-82
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• 2001

Visual cryptography made it possible to decrypt the Information encrypted by thresholding scheme not with digital system but with human vision system. This method, however, has some limit in it because of the rack of resolution in both the spatial and amplitude domain. Optical visual cryptography, which used laser system instead of human eyesight, was proposed by conjunction of the optical theory with the cryptography. However, it also had some difficulties because it did not overcome the existing problem of visual cryptography completely. The problem occurred in the process of transferring data processing system from visual to optics. Therefore, it is appropriate to approach these problems in terms of optics. In this paper, we analysis, in the aspect of frequency, the security characteristics and the noise level occurred in the process of optical visual encryption.

• Journal of Digital Contents Society
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• v.13 no.4
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• pp.531-538
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• 2012

Visual cryptography is a scheme that recovers secret image through human vision by overlapping distributed share images without cryptographic operations. Distribution methods are still being developed for improving quality of shared images keeping size of images invariant and enhancing robustness against resize of images. Since visual cryptography only uses shared images, this fact is exploited to attack. From this fact, a scheme safe for sharing distributed images is needed. In this paper, a new visual cryptographic scheme using cover image is proposed. This scheme reduces the chance of detection against steganalysis and increases security. In addition, this paper shows that the proposed scheme can completely decrypt secret image without creating noise.

• Convergence Security Journal
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• v.19 no.5
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• pp.37-45
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• 2019

Video security systems change from analog based systems to network based CCTVs. Therefore, such network based systems are always exposed not only to threats of eavesdropping and hacking, but to personal damage or public organizations' damage due to image information leakage. Therefore, in order to solve the problem, this study conducts a comparative analysis on proposes the optimal ECC(Elliptic Curve Cryptography) scalar multiplication algorithms for image information protection in data communication process and thereby proposes the optimal operation algorithm of video security system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.7
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• pp.2532-2553
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• 2014

In Asiacrypt 2003, Al-Riyami and Paterson proposed the notion of certificateless cryptography, a technique to remove key escrow from traditional identity-based cryptography as well as circumvent the certificate management problem of traditional public key cryptography. Subsequently much research has been done in the realm of certificateless encryption and signature schemes, but little to no work has been done for the identification primitive until 2013 when Chin et al. rigorously defined certificateless identification and proposed a concrete scheme. However Chin et al.'s scheme was proven in the random oracle model and Canetti et al. has shown that certain schemes provable secure in the random oracle model can be insecure when random oracles are replaced with actual hash functions. Therefore while having a proof in the random oracle model is better than having no proof at all, a scheme to be proven in the standard model would provide stronger security guarantees. In this paper, we propose the first certificateless identification scheme that is both efficient and show our proof of security in the standard model, that is without having to assume random oracles exist.

• The Journal of Korean Association of Computer Education
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• v.14 no.4
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• pp.43-51
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• 2011

Recently, by the development of information technology, we can get various information from anywhere in real time. However, personal information is exposed to threats which may incur unwanted information leakage. Cryptography serves as a primary study to prevent this leakage. However, some theories of cryptography are based on complex mathematical theories which make many people confused. Therefore, in this paper, we develope a software which is helpful to understand RSA algorithm, which is widely used algorithm in digital signature to protect personal information.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.5
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• pp.815-824
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• 2013

Traditionally embedded microprocessors is considered as a device for low- and simple-computations because of its limited computing power and constrained resources. However high-end embedded devices have been developed and many applications are getting feasible in the embedded devices. To provide secure and robust service environments, security on embedded devices are in order. Recently many research results on embedded devices have been proposed. In this paper, we explore various cryptography implementation results on representative 8-, 16- and 32-bit embedded processors including AVR, MSP and ARM. This report would be helpful for following researchers who are interested in cryptography implementation techniques on resource constrained devices.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5625-5641
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• 2017

Certificateless public key cryptography resolves the certificate management problem in traditional public key cryptography and the key escrow problem in identity-based cryptography. In recent years, some good results have been achieved in speeding up the computation of bilinear pairing. However, the computation cost of the pairing is much higher than that of the scalar multiplication over the elliptic curve group. Therefore, it is still significant to design cryptosystem without pairing operations. A multi-signer universal designated multi-verifier signature scheme allows a set of signers to cooperatively generate a public verifiable signature, the signature holder then can propose a new signature such that only the designated set of verifiers can verify it. Multi-signer universal designated multi-verifier signatures are suitable in many different practical applications such as electronic tenders, electronic voting and electronic auctions. In this paper, we propose a certificateless multi-signer universal designated multi-verifier signature scheme and prove the security in the random oracle model. Our scheme does not use pairing operation. To the best of our knowledge, our scheme is the first certificateless multi-signer universal designated multi-verifier signature scheme.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.498-501
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• 2002

In the process of Log-In to the system, clear User authentication is the beginning of the information protection service. In the open communication system of today, it is true that a password as security instrument and the inner mechanism of the system and cryptography algorithm for the support of this are also poor. For this reason, this dissertation had a final aim to design the user authentication system, which offer the accuracy and safety. It used RSA and CBC mode of DES as cryptography algorithm and used the Challenge-Response scheme at a authentication protocol and designed the User authentication system to which user access using one time password, output of token to guarantee the safety of the authentication protocol. Alto by using the Public key cryptography algorithm, it could embody the more safe User authentication system.