• ETRI Journal
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• 제33권1호
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• pp.60-70
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• 2011

Software is completely exposed to an attacker after it is distributed because reverse engineering is widely known. To protect software, techniques against reverse engineering are necessary. A code encryption scheme is one of the techniques. A code encryption scheme encrypts the binary executable code. Key management is the most important part of the code encryption scheme. However, previous schemes had problems with key management. In an effort to solve these problems in this paper, we survey the previous code encryption schemes and then propose a new code encryption scheme based on an indexed table. Our scheme provides secure and efficient key management for code encryption.

• 정보보호학회논문지
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• 제21권5호
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• pp.3-13
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• 2011

2004년 Boneh et. al. 은 송신자가 전송한 검색어에 대한 암호문과 수신자가 제공한 쿼리 생성에 사용된 검색어의 동일성을 서버가 검사할 수 있는 PEKS 스킴을 제안하였다. 이후 Yang et. al. 은 서로 다른 공개키로 암호화된 암호문의 비교를 통해 암호화된 메시지의 동일성을 검사하는 기법인 Probabilistic Public Key Encryption with Equality Test(PEET)을 제안하였다. PEET 기술은 메시지 부분을 검색어로 대체해서 암호화할 경우 Keyword guessing attacks에 대한 안전성을 보장하지 못하고 검색가능 암호화 기법들에서 일반적으로 고려되고 있는 안전성의 기준인 IND-CPA 안전성을 제공하지 못한다. 본 논문에서는 Keyword guessing attacks에 안전하며 IND-CPA를 만족하는 고정된 검사자를 고려한 메시지 동일성 검사 공개키 암호시스템(public key encryption with equality test with designated tester. dPEET)을 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권11호
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• pp.3182-3203
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• 2023

With the growing adoption of cloud-based technologies, maintaining the privacy and security of cloud data has become a pressing issue. Privacy-preserving encryption schemes are a promising approach for achieving cloud data security, but they require careful design and implementation to be effective. The integrated approach to cloud data security that we suggest in this work uses CogniGate: the orchestrated permissions protocol, index trees, blockchain key management, and unique Opacus encryption. Opacus encryption is a novel homomorphic encryption scheme that enables computation on encrypted data, making it a powerful tool for cloud data security. CogniGate Protocol enables more flexibility and control over access to cloud data by allowing for fine-grained limitations on access depending on user parameters. Index trees provide an efficient data structure for storing and retrieving encrypted data, while blockchain key management ensures the secure and decentralized storage of encryption keys. Performance evaluation focuses on key aspects, including computation cost for the data owner, computation cost for data sharers, the average time cost of index construction, query consumption for data providers, and time cost in key generation. The results highlight that the integrated approach safeguards cloud data while preserving privacy, maintaining usability, and demonstrating high performance. In addition, we explore the role of differential privacy in our integrated approach, showing how it can be used to further enhance privacy protection without compromising performance. We also discuss the key management challenges associated with our approach and propose a novel blockchain-based key management system that leverages smart contracts and consensus mechanisms to ensure the secure and decentralized storage of encryption keys.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.491-498
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• 2001

본 논문에서는 개방형 통신상에서 전송중인 데이터를 암호화시켜 정보의 노출을 방지하고 송신자가 인정한 수신자만이 이러한 정보를 받을 수 있도록 한 암호화 알고리즘을 제시한다. 암호화의 방법에는 크게 관용키 암호화 방법과 공개키 암호화 방법으로 나누는데 본 논문에서는 혼합형 암호화 방식의 개념을 이용했다. 이 알고리즘은 통신시간과 저장공간을 절약하기 위해 전송할 데이터를 압축한 다음 암호화시키게 되며, 암호화 key를 생성하기 위한 파라미터로서 키를 생성하게 하는 것이 특징이다. 파라미터는 키 값이 생성됨과 동시에 전송되고 매 26회마다 파라미터를 변경시켜 키를 재생성 시킨다. 암호화키의 구성요소인 random number 는 table 형태로 저장되는데 키가 40회마다 table을 재편성 key의 보안을 강화하였다. 이렇게 생성된 키와 원래 데이터는 연산과정을 거쳐 암호화가 이루어진다. 복호화는 전송된 파라미터를 조사해 복호화 키를 구한 다음 암호화 동작의 역순으로 수행한다. 본 논문에서 제시한 알고리즘을 구현 및 평가결과는 100KB 메시지 0.0152/sec 정도로 빠른 수행이 되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권2호
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• pp.1064-1079
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• 2019

Information security has become increasingly important with the rapid development of mobile devices and internet. An efficient encryption system is a key to this end. In this paper, we propose an image encryption method based on the cross diffusion of two chaotic maps. We use two chaotic sequences, namely the Logistic map and the Chebyshev map, for key generation which has larger security key space than single one. Moreover, we use these two sequences for further image encryption diffusion which decreases the correlation of neighboring pixels significantly. We conduct extensive experiments on several well-known images like Lena, Baboon, Koala, etc. Experimental results show that our algorithm has the characteristics of large key space, fast, robust to statistic attack, etc.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.6116-6132
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• 2017

The proxy re-encryption allows an intermediate proxy to convert a ciphertext for Alice into a ciphertext for Bob without seeing the original message and leaking out relevant information. Unlike many prior identity based proxy re-encryption schemes which are based on the number theoretic assumptions such as large integer factorization and discrete logarithm problem. In this paper, we first propose a novel identity based proxy re-encryption scheme which is based on the hardness of standard Learning With Error(LWE) problem and is CPA secure in the standard model. This scheme can be reduced to the worst-case lattice hard problem that is able to resist attacks from quantum algorithm. The key step in our construction is that the challenger how to answer the private query under a known trapdoor matrix. Our scheme enjoys properties of the non-interactivity, unidirectionality, anonymous and so on. In this paper, we utilize primitives include G-trapdoor for lattice and sample algorithms to realize simple and efficient re-encryption.

• 한국통신학회논문지
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• 제37권4B호
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• pp.288-299
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• 2012

최근 모바일 클라우드 환경에서 공유되는 데이터의 기밀성과 유연성있는 접근제어를 보장하기 위해서 KP-ABE(Key Policy-Attribute Based Encryption)와 PRE(Proxy Re-Encryption)를 활용한 시스템 모델이 제안되었다. 그러나 기존 방식은 철회된 사용자와 클라우드 서버간의 공모 공격으로 데이터 기밀성을 침해하게 된다. 이러한 문제를 해결하기 위해서 제안 방식은 클라우드 서버에 저장되는 데이터 파일(data file)을 분산 저장하여 데이터 기밀성을 보장하고 비밀분산(Secret Sharing)를 통해서 프록시 재암호화키에 대한 변조 공격을 방지한다. 그리고 제안방식을 의료 환경에 적용한 프로토콜 모델을 구성한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권7호
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• pp.2703-2718
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• 2015

Nowadays, public cloud storage is gaining popularity and a growing number of users are beginning to use the public cloud storage for online data storing and sharing. However, how the encrypted data stored in public clouds can be effectively shared becomes a new challenge. Proxy re-encryption is a public-key primitive that can delegate the decryption right from one user to another. In a proxy re-encryption system, a semi-trusted proxy authorized by a data owner is allowed to transform an encrypted data under the data owner's public key into a re-encrypted data under an authorized recipient's public key without seeing the underlying plaintext. Hence, the paradigm of proxy re-encryption provides a promising solution to effectively share encrypted data. In this paper, we propose a new certificate-based proxy re-encryption scheme for encrypted data sharing in public clouds. In the random oracle model, we formally prove that the proposed scheme achieves chosen-ciphertext security. The simulation results show that it is more efficient than the previous certificate-based proxy re-encryption schemes.

• 한국전자거래학회지
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• 제7권1호
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• pp.167-186
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• 2002

The encryption of a file on a PC before saving can maintain security of the file. However, if the key for the encrypted file is lost or damaged, the encrypted file can not be decrypted, resulting in serious economical loss to the user or the user group. In order to minimize the economical loss a secure and reliable key recovery technology is required. Presented in this paper is the development and evaluation of PKRS (PC based Key Recovery System) which supports encryption and decryption of file and recovery of the encrypted file in emergency. The encapsulating method, which attaches key recovery information to encrypted file, is applied to the PKRS. In addition, the PKRS is developed and evaluated according to the requirements of Requirements for Key Recovery Products proposed by NIST and requirements of Common Criteria 2.0 to prove the safety and reliability of the information security system. This system is applicable to a PC and can be further extended to internet or intranet environment information system where in encryption and recovery of file is possible.

• 한국통신학회논문지
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• 제17권6호
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• pp.629-639
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• 1992

본 논문에서 근거리 통신망에서의 정보보호 취약성, 요구 서비스, 정보보호 적용대안에 대하여 정리하고, 근거리 통신망에 적합한 새로운 키이 분배 방식을 제안하였다. 제안된 방식은 Time Quantum을 암호화 키이에 적용하여 암호화 키이 사용시간과 키이를 이용한 암호화 메시지 양을 제한하였다. 제안된 방식은 키이 concurrency와 상대방에 대한 인증을 더욱 확실하게 할 수 있으며, 프레임 단위 도청으로 인하여 암호화 키이 노출이 발생하더라도 전체 전송 메시지의 내용을 알 수 없으므로 정보보호 및 안정성을 더욱 강화하는 특징을 갖도록 하였다.