• Journal of KIISE:Computer Systems and Theory
• /
• v.30 no.5_6
• /
• pp.239-249
• /
• 2003

The secret sharing is the basic concept of the threshold cryptosystem and has an important position in the modern cryptography. At 1995, Jarecki proposed the proactive secret sharing to be a solution of existing the mobile adversary and also proposed the share renewal scheme for (k, n) threshold scheme. For n participants in the protocol, his method needs $O(n^2)$ modular exponentiation per one participant. It is very high computational cost and is not fit for the scalable cryptosystem. In this paper, we propose the efficient share renewal scheme that need only O(n) modular exponentiation per participant. And we prove our scheme is secure if less than img ${\frac{1}{2}}$ n-1 adversaries exist and they are static adversary.

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

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.5
• /
• pp.472-476
• /
• 2008

In this paper, we propose a simple and user friendly visual secret sharing scheme based on binary image. The proposed scheme is a new information hiding method which uses only bit-wise exclusive-or (XOR) operation and NOT operation to share a secret binary image information in the user friendly binary images. The proposed scheme has the following merits: (1) It provides efficient embedding and reconstruction algorithms. (2) It provides lossless and perfect reconstruction of the secret binary image. (3) It provides the detection method of its own group by sharing the user friendly image. (4) It can share same sized secret image such as original cover image unlike previous methods.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.10
• /
• pp.3128-3137
• /
• 2000

Secret sharing scheme is a cryptographic protocol in which a dealer distribures shares of a secret among a set of participants such that only authorized set of participants can recover the secret at a later. Secret sharing is an important cryptographic primitive in management of secret information, secure multiparty protocol and group-oriented cryptography, etc. In this paper, we propose an efficient, on-line secret sharing scheme based on one-way hash function. This scheme provides the property to share multiple secrets and allows participants to be added/deleted dynamically, without having to redistributo new shares. Proposed scheme has advantage to detect cheating and identify of all cheater, regardless of then number. Frthermore, it is more eficient than previous schemes.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.16 no.2
• /
• pp.113-119
• /
• 2006

Image steganography is a secret communication method used to transmit secret messages that have been embedded into an image. To accommodate a secret message in a digital image, the original cover image is modified by the embedding algorithm. As a result, a stego image is obtained. The sender hides the secret message in a cover image that has no meaning, and then transmits the stego image to the receiver. In this paper, we propose a steganographic method based on spatial domain to embed a secret message using a difference value of two consecutive pixels and a secret quantization range. Especially, we use the modular operation for increasing of insertion information. Through experiments, we have shown that the proposed method has much mon payload capacity, average 60 percent, than some existing methods by using modular operation.

• Journal of Korea Multimedia Society
• /
• v.16 no.5
• /
• pp.577-590
• /
• 2013

Shamir's (k,n)-threshold secret sharing scheme is not secure against cheating by attacker because the signature of participants is omitted. To prevent cheating, many schemes have been proposed, and a proactive secret sharing is one of those. The proactive secret sharing is a method to update shares in the secret sharing scheme at irregular intervals. In this paper, a proactive image secret sharing scheme over $GF(2^8)$ is proposed for the first time. For the past 30 years, Galois field operation is widely used in order to perform the efficient and secure bit operation in cryptography, and the proposed scheme with update phase of shadow image over $GF(2^8)$) at irregular intervals provides the lossless and non-compromising of secret image. To evaluate security and efficiency of images (i.e. cover and shadow images) distortion between the proposed scheme and the previous schemes, embedding capacity and PSNR are compared in experiments. The experimental results show that the performances of the embedding capacity and image distortion ratio of the proposed scheme are superior to the previous schemes.

• Digital Contents
• /
• no.2 s.141
• /
• pp.108-113
• /
• 2005

회사의 중대한 콘텐츠 관련 정보나 첨단 기술의 유출에 관한 보고서에 따르면 영업 비밀의 유출을 시도하는 주대상은 퇴직사원이 69.4%, 현직사원이 16.7%로 나타났다. 그러나 퇴사후 몇 년 간 취업제한 비밀유지 서약 등 퇴직자에 대한 보안관리를 공식화하고 있는 기업은 49.5%에 불과하다. 대부분의 IT중소 벤처기업들은 영업 비밀보호에 대한 적절한 법적 장치를 마련하고 있지 않는 등 그 중요성을 인식 하지 못하고 있어 향후 심각한 분쟁의 가능성을 내포하고 있다. 이에 이번 호에서는 디지털콘텐츠 기업을 위한 영업 비밀 보호 방안에 관한 법적 문제를 다로가자 한다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 1998.12a
• /
• pp.67-82
• /
• 1998

컴퓨터 통신망과 인터넷의 발달로 등장한 전자상거래는 안전성과 신뢰성이 보장되어야 한다. 이를 위해, 본 논문에서는 기존의 인증기관과 전자지갑을 기능별 구조로 고찰한뒤 비밀키의 안전도를 개선할 수 있는 전자상거래에서의 인증 프로토콜을 제안하고 구현한다. 제안한 인증 프로토콜은 사용자의 공개키/비밀키 쌍을 전자지갑이 직접 생성하고 인증기관은 사용자의 공개키만을 전자서명하도록 함으로써 전자상거래 시스템에서 사용자 비밀키에 더 높은 안전성과 신뢰성을 제공한다. 또한, 공개키 암호시스템으로는 키 길이와 메모리 면에서 효율적인 타원곡선 암호시스템을 사용한다.

• Patent21
• /
• s.94
• /
• pp.12-15
• /
• 2011

최근 국내 외 기술유출이 늘어남에 따라, 우리 기업이 보유하고 있는 영업비밀에 대한 관리 및 보호에 관심이 모아지고 있다. 그러나 기술유출 관련 분쟁 발생시, 침해 사실을 입증하는데 가장 기본이 되는 영업비밀의 존재와 보유시점을 입증하기란 현실적으로 쉽지 않은 일이다. 그러나, 특허청과 한국특허정보원이 공동으로 제공하고 있는 "영업비밀 원본 증병 서비스(www.tradesecret.or.kr)" 는 누구나 쉽고 간편하게 이용할 수 있다는 장점에 기존 기술유출 관련 증거 자료를 확보하는데 소요되는 많은 비용과 시간을 절감할 수 있다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 2001.11a
• /
• pp.132-138
• /
• 2001

본 논문에서는 타원곡선 스칼라 곱셈에 대하여 새로운 형태의 hardware fault cryptanalysis를 적용해 보고, 이에 대한 대응방법으로서 비밀키 blinding방법을 제안하고 있다. 또한 비밀키 blinding 방법을 사용함으로써 늘어나는 연산량을 기존의 대응 방법과 비교하고, 이러한 비밀키 blinding방법이 사용될 수 있는 범위에 대해 다루고 있다.