• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권2호
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• pp.764-785
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• 2018

In this paper, we present a new public key encryption scheme with equality test (PKEwET). Compared to other PKEwET schemes, we find that its security can be improved since the proposed scheme is based on non-Abelian factorization problems. To our knowledge, it is the first scheme regarding equality test that can resist quantum algorithm attacks. We show that our scheme is one-way against chosen-ciphertext attacks in the case that the computational Diffie-Hellman problem is hard for a Type-I adversary. It is indistinguishable against chosen-ciphertext attacks in the case that the Decisional Diffie-Hellman problem is hard in the random oracle model for a Type-II adversary. To conclude the paper, we demonstrate that our scheme is more efficient.

• Journal of information and communication convergence engineering
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• 제8권4호
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• pp.437-442
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• 2010

Ubiquitous mobile computing is becoming easier and more attractive in this ambient technological Internet world. However, some portable devices such as Personal Digital Assistant (PDAs) and smart phones are still encountering inherent constraints of limited storages and computing resources. To alleviate this problem, we develop a cost-effective protocol, iATA to transfer ATA commands and data over TCP/IP network between mobile appliances and stationary servers. It provides mobile users a virtual storage platform which is physically resided at remote home or office. As communications are made through insecure Internet connections, security risks of adopting this service become a concern. There are many reported cases in the history where attackers masquerade as legitimate users, illegally access to network-based applications or systems by breaking through the poor authentication gates. In this paper, we propose a mutual authentication and secure session termination scheme as the first and last defense steps to combat identity thief and fraud threat in particular for iATA services. Random validation factors, large prime numbers, current timestamps, one-way hash functions and one-time session key are deployed accordingly in the scheme. Moreover, we employ the concept of hard factorization problem (HFP) in the termination phase to against fraud termination requests. Theoretical security analysis discussed in later section indicates the scheme supports mutual authentication and is robust against several attacks such as verifiers' impersonation, replay attack, denial-of-services (DoS) attack and so on.

• Journal of Information Processing Systems
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• 제8권4호
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• pp.567-574
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• 2012

This paper presents a strong designated verifiable signcryption scheme, in which a message is signcrypted by a signcryptor and only a specific receiver, who called a "designated verifier", verifies it using his own secret key. The scheme is secure, as an adversary can not verify the signature even if the secret key of the signer is compromised or leaked. The security of the proposed scheme lies in the complexity of solving two computationally hard problems, namely, the Discrete Logarithm Problem (DLP) and the Integer Factorization Problem (IFP). The security analysis of the scheme has been done and it is proved that, the proposed scheme can withstand an adaptive chosen ciphertext attack. This scheme can be very useful in organizations where there is a need to send confidential documents to a specific recipient. This scheme can also be applicable to real life scenarios, such as, e-commerce applications, e-banking and e-voting.

• 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.

• 서비스연구
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• 제5권2호
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• pp.71-81
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• 2015

RSA 공개키 암호화 알고리즘에서는 소수, 키 생성, 소인수분해, 오일러 함수, 키 셋업, 합동식과 법, 지수 처리가 응용된다. 이와같은 알고리즘의 토대는 수학원리이다. 수학원리 중에서 첫 번째 개념은 소수를 구하여 응용하는 방법에서 출발한다. 두 개의 매우 큰 소수의 곱을 구하는 것은 용이 하지만 그 곱에서 원래의 두 개의 소수를 역 추적하는 것은 매우 어렵다는 원리를 이용한다. p와 q를 매우 큰 소수라 하면 이 두 개의 곱 $n=p{\times}q$를 구하는 것은 쉽지만 역으로, 합성수인 n에서 p와 q를 추적하는 방법은 거의 불가능하다. RSA 암호화 알고리즘에서는 수학적으로 역함수 계산이 어려운 일방향 함수를 구현하기 위해 자리수가 많은 양의 정수의 소인수 분해 문제를 사용하고 있다. 역 방향으로의 계산을 어렵게 하기 위해 mod의 개념을 소인수 분해 문제에 더해서 사용한다. 암호화에 대한 관심분야는 대개 알고리즘 구현과 사용에 집중되고 있지만 막상 암호 알고리즘을 처음 도입하는 경우에는 어떤 프로세스를 거쳐야 현장 업무에 적용되는지를 알 수 없다. 본 연구는 공개키 알고리즘 속성 진단을 기반으로 한 현장 업무 암호화 적용 프로세스 방안을 제시한다.