• Journal of Communications and Networks
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• v.10 no.2
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• pp.221-227
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• 2008

The proposed zone-based self-organized clustering broadcasts neighbor information to only a zone with the same ID. Besides, the zone-based self-organized clustering with unique IDs can communicate securely even if the state transition of nodes in zone-based self-organized clustering is threatened by corrupted nodes. For this security, the Byzantine agreement protocol with proactive asynchronous verifiable secret sharing (AVSS) is considered. As a result of simulation, an efficiency and a security of the proposed clustering are better than those of a traditional clustering. Therefore, this paper describes a new and extended self-organized clustering that securely seeks to minimize the interference in mobile ad hoc networks (MANETs).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.3401-3420
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• 2018

Pixel expansion and contrast are two major performance parameters for visual cryptography scheme (VCS), which is a type of secret image sharing. Random Grid (RG) is an alternative approach to solve the pixel expansion problem. Chen and Tsao proposed the first (k, n) RG-based VCS, and then Guo et al., Wu et al., Shyu, and Yan et al. significantly improved the contrast in recent years. However, the investigations on improving the contrast of threshold RG-based VCS are not sufficient. In this paper, we develop a contrast-improved algorithm for (k, n) RG-based VCS. Theoretical analysis and experimental results demonstrate that the proposed algorithm outperformers the previous threshold algorithms with better visual quality and a higher accuracy of contrast.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.10
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• pp.4198-4213
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• 2020

Data encryption, particularly application-level data encryption, is a common solution to protect data confidentiality and deal with security threats. Application-level encryption is a process in which data is encrypted before being sent to the database. However, cryptography transforms data and makes the query difficult to execute. Various studies have been carried out to find ways in order to implement a searchable encrypted database. In the current paper, we provide a new encrypting method and querying on encrypted data (ZSDB) for different data types. It is worth mentioning that the proposed method is based on secret sharing. ZSDB provides data confidentiality by dividing sensitive data into two parts and using the additional server as Dictionary Server. In addition, it supports required operations on various types of data, especially LIKE operator functioning on string data type. ZSDB dedicates the largest volume of execution tasks on queries to the server. Therefore, the data owner only needs to encrypt and decrypt data.

• The Journal of the Korea Contents Association
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• v.4 no.3
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• pp.53-60
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• 2004

In this paper we present user authentication and key distribution using threshold PKC(Public Key Cryptosystem), which is secure against the dictionary attack. The n servers hold a t-out-of-n sharing of the dealer's secret key. When the server authenticate a user, at least f of them cooperate they can reconstruct password verifier.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.760-763
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• 2004

We propose a biometrical information security method based on Optical Visual Cryptography in that a fingerprint data is processed by Secret Sharing method taking into account the Optical Visual Cryptography and a part of shared data transmitted through an open network. Whenever necessary the owner or the fingerprint can be authenticated by submitting his fingerprint with the other shared information.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.313-315
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• 2004

인터넷과 같은 항상 변화하고 있는 거대한 네트워크에서는 안전한 전자거래를 위해 않은 키들과 메시지 확장 없이 그룹의 구성원이 다른 구성원이나 그룹에게 전해진 메시지 인증이 보장되어야 한다. 본 논문에서는 이를 위한 효율적인 그룹 서명 기법인 그룹의 공개키 수정없이 그리고 나머지 구성원들이 새로운 인증을 요구하지 않는 인증방법으로, 항상 변화하는 인터넷에서 신뢰기관인 중앙 인증기관이 없는 쓰레시홀드 크립토그래피(Threshold Cryptography)를 가진 비잔틴 어그리먼트 프로토콜(Byzantine Agreement Protocol)을 제안한다 아울러 쓰레시홀드 크립토그래피는 키 관리 문제를 피하고 키 분산을 하기 위해 신뢰된 분배자 없이 호모모르픽 시크리트 쉐어링의 Proactive AVSS(Asynchronous Verifiable Secret Sharing)를 제시한다.

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

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.4
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• pp.35-41
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• 2017

This paper introduces a new method for storing a private key. This method can be achieved by dividing the private key into "n" pieces by a (k, n) secret sharing method, and then storing each piece into photo files utilizing a steganography method. In this way, a user can restore a private key as long as he can remember the locations of "k" photos among the entire photo files. Attackers, meanwhile, will find it extremely difficult to extract the private key if a user has hidden the pieces of the private key into numerous photo files stored in the system. It also provides a high degree of user convenience, as the user can restore the private key from his memory of k positions among n photo files. Coupled with this, a certain level of security can be guaranteed because the attacker cannot restore a private key, even if he knows k-1 photo file locations.

• Journal of Internet Computing and Services
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• v.13 no.5
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• pp.55-64
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• 2012

Nowadays, as Cloud computing becomes popular, a need for a DFS(distributed file system) is increased. But, in the current Cloud computing environments, there is no DFS framework that is sufficient to protect sensitive private information from attackers. Therefore, we designed and proposed a secure scheme for distributed file systems. The scheme provides confidentiality and availability for a distributed file system using a secret sharing method. In this paper, we measured the speed of encryption and decryption for our proposed method, and compared them with that of SEED algorithm which is the most popular algorithm in this field. This comparison showed the computational efficiency of our method. Moreover, the proposed secure read/write model is independent of Hadoop DFS structure so that our modified algorithm can be easily adapted for use in the HDFS. Finally, the proposed model is evaluated theoretically using performance measurement method for distributed secret sharing model.

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