• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.31 no.5
• /
• pp.863-874
• /
• 2021

Distributed key generation (DKG) with trustless setup is a cryptographic protocol that distributes Shamir secret shares of a private key to participants while keeping the actual private key hidden to the participants. Also, by extending it to a threshold signature protocol, digital signatures can be generated without construction of private keys. This paper proposes a recovery protocol maintaining trustless setup assumptions, in particular to the useful (1,3) share structure. The proposed protocol meets same levels of security requirements with DKG in terms of correctness and secrecy. The protocol can also enable delegation and revocation of digital sign rights for blockchain-based asset management.

• The Transactions of the Korea Information Processing Society
• /
• v.13 no.2
• /
• pp.34-40
• /
• 2024

Secret sharing is a cryptographic technique that involves dividing a secret or a piece of sensitive information into multiple shares or parts, which can significantly increase the confidentiality of a secret. There has been a lot of research on secret sharing for different contexts or situations. Tassa's conjunctive secret sharing method employs polynomial derivatives to facilitate hierarchical secret sharing. However, the use of derivatives introduces several limitations in hierarchical secret sharing. Firstly, only a single group of participants can be created at each level due to the shares being generated from a sole derivative. Secondly, the method can only reconstruct a secret through conjunction, thereby restricting the specification of arbitrary secret reconstruction conditions. Thirdly, Birkhoff interpolation is required, adding complexity compared to the more accessible Lagrange interpolation used in polynomial-based secret sharing. This paper introduces the multi-compartment secret sharing method as a generalization of the conjunctive hierarchical secret sharing. Our proposed method first encrypts a secret using external groups' shares and then generates internal shares for each group by embedding the encrypted secret value in a polynomial. While the polynomial can be reconstructed with the internal shares, the polynomial just provides the encrypted secret, requiring external shares for decryption. This approach enables the creation of multiple participant groups at a single level. It supports the implementation of arbitrary secret reconstruction conditions, as well as conjunction. Furthermore, the use of polynomials allows the application of Lagrange interpolation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.2
• /
• pp.390-396
• /
• 2005

With the spread of computer and development of internet service, the varied contents and digital data has been produced, then provided. The digital contents are more efficiently able to be created, produced, provided as well as distributed, on the other hand, its own copyrights seem to be more easily broken than analogue contents due to the convenience to make copies of original contents. Therefore, protecting copyrights recently become the key issue. DRM(Digital Rights Management) is the current technology to protect digital contents from duplication but it sometimes causes problems in the key-management. In this thesis, we would first like to analyze DRM and find out some trouble in the key-management of it. Finally, we will show CDMS(CEK Distributed Management System) to improve DRM out of the key-management problem and continue to study for better key-management system with it.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 1996.11a
• /
• pp.251-260
• /
• 1996

Naor & Shamir는 시각 암호에 관한 기본 개념을 제시하고 이를 위한 구성법을 제안하고 있다. 이는 복잡한 암호학적인 계산 없이 숨겨진 비밀을 복호하는 새로운 암호형태로서 대단히 안전하고 구현이 용이하다는 장점을 가지고 있다. 본 논문에서는 (2, n)시각 비밀 분산법의 여러 방법들에 대하여 고찰한다 또한, 시각 암호의 실질적인 응용의 효과를 기대할 수 있는 농담화상에 적용하기 위한 시각 암호의 구성법과실제 구현결과를 보인다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2013.11a
• /
• pp.892-893
• /
• 2013

스마트 그리드 환경에서 발생하는 민감한 개인정보 데이터에 대한 보안을 통해 소비자의 개인 프라이버시를 보호 하고자 데이터 비밀분산 관련 기법을 소개한 뒤 이 기법에 대한 문제점을 설명 하고자 한다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.04a
• /
• pp.365-367
• /
• 2003

핑거프린팅 기법은 암호학적인 기법들을 이용하여 디지털 데이터를 불법적으로 재배포한 사용자를 찾아냄으로써 디지털 데이터의 저작권을 보호한다. 익명성이 보장되는 핑거프린팅 기법은 대칭적인 기법과 달리 사용자만이 핑거프린트가 삽입된 데이터를 알 수 있고 비대칭 기법과 달리 데이터가 재배포되기 전에는 사용자의 익명성이 보장되는 기법이다. 본 논문에서는 사용자의 익명성이 보장되는 새로운 핑거프린팅 기법을 제안한다. 비밀분산법을 이용하여 사용자의 신원정보를 숨겨두었다가 재배포 발견시 조정자에게 누가 재배포하였는지 증거를 제출함으로써 재배포자의 배포 사실을 증명한다. 또한 등록시에 Schnorr 서명을 이용하여 고발된 사용자가 범행을 부인할 수 없도록 한다. 제안된 방법은 이산대수문제와 양자간 안전한 계산과정의 안전성에 근거하여 사용자의 익명성이 보장된다.

• Journal of KIISE:Computer Systems and Theory
• /
• v.31 no.5_6
• /
• pp.353-359
• /
• 2004

The illegal copying and redistribution of digitally-stored information is a crucial problem to distributors who electronically sell digital data. Fingerprinting scheme is a techniques which supports copyright protection to track redistributors of electronic information using cryptographic techniques. Anonymous fingerprinting schemes, differ from symmetric fingerprinting, prevent the merchant from framing a buyer by making the fingerprinted version known to the buyer only. And the scheme, differ from asymmetric fingerprinting, allows the buyer to purchase goods without revealing her identity to the merchant. In this paper, a new anonymous fingerprinting scheme based on secret sharing is introduced. The merchant finds a sold version that has been distributed, and then he is able to retrieve a buyer's identity and take her to court. And Schnorr's digital signature prevents the buyer from denying the fact he redistributed. The buyer's anonymity relies on the security of discrete logarithm and secure two-party computations.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
• /
• v.7 no.2
• /
• pp.311-319
• /
• 2017

Recently invasion of privacy problem in medical information have been issued following the interest in secondary use of large medical information. These large medical information is very useful information that can be used in various fields such as disease research and prevention. However, due to the privacy laws such as Privacy Act and Medical Law, these informations including patients or health professionals' personal information are difficult to utilize secondary. Accordingly, various methods such as k-anonymity, l-diversity and differential-privacy that can be utilized while protecting privacy have been developed and utilized in this field. In this paper, we study differential privacy processing procedure, one of various methods, and find out about the differential privacy problem using Laplace noise. Finally, we propose a new method using the Shamir's secret sharing method and symemetric key encryption algorithm such as AES for this problem.

• Journal of Broadcast Engineering
• /
• v.21 no.3
• /
• pp.412-424
• /
• 2016

Broadcast encryption (BE) is a cryptographic primitive that enables a sender to broadcast a message to a set of receivers in a secure channel. The efficiency of BE is measured by three factors: ciphertext transmission cost, user storage cost, and computational cost for decryption. In general, BE is applied to the environments where a large number of receivers should be accommodated, so that the transmission cost is considered as being the most important factor. In this paper, we suggest a new BE system, using Shamir's secret sharing method, which considerable reduces the transmission cost. In comparison to the previous Subset Difference (SD) system, the transmission size of our BE is longer until $r{\leq}\sqrt{n}$, but get shorter when $r{\geq}\sqrt{n}$ for number of revoked users and n number of total users. We show that the advantage can be achieved at the slight expense of both the storage and computational costs.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.11
• /
• pp.79-84
• /
• 2015

Steganography is to conceal the existence of secrete data itself. The Emulab is a framework to provide real systems and network topology that can set up at anytime by researchers. In this paper, we show that steganography techniques can be applied in the Emulab environment. Steganography methods are evaluated on a standalone and sharing environments using the color bitmap images. The cover image is divided into RGB channels and then embedded the secret data at each client. The experimental results demonstrate that execution time is better in client/server environment as cover image size is increasing.