• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.545-551
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• 2012

In this paper, we propose a new cryptosystem based on the IQC depended on the complexity of class number and intractibility of factoring integer, and introduce two algorithm which reduce encryption and decryption times. To recognize the security of the cryptosystem, we take a simple example to analyze the complexities of public key and secret key and then introduce the operating process of the cryptosystem.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.1
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• pp.43-54
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• 2002

McEliece introduced a public-key cryptosystem based on Algebraic codes, specially binary classical Goppa which have a good decoding algorithm and vast number of inequivalent codes with given parameters. And the advantage of this system low cost of their encryption and decryption procedures compared with other public-key systems specially RSA, ECC based on DLP(discrete logarithm problem). But in [1], they resent new attack based on probabilistic algorithm to find minimum weight codeword, so for a sufficient security level, much larger parameter size [2048, 1608,81]is required. Then the big size of public key make McEliece PKC more inefficient. So in this paper, we will propose New Type PKC using q-ary Hyperelliptic code so that with smaller parameter(1 over 3) but still work factor as hi인 as McEliece PKC and faster encryption, decryption can be maintained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5537-5555
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• 2017

Having the characteristics of unlinkability, anonymity, and unforgeability, blind signatures are widely used for privacy-related applications such as electronic cash, electronic voting and electronic auction systems where to maintain the anonymity of the participants. Among these applications, the blinded message is needed for a certain purpose by which users delegate signing operation and communicate with each other in a trusted manner. This application leads to the need of proxy blind signature schemes. Proxy blind signature is an important type of cryptographic primitive to realize the properties of both blind signature and proxy signature. Over the past years, many proxy blind signature algorithms have been adopted to fulfill such task based on the discrete logarithm problem (DLP) and the elliptic curve discrete log problem (ECDLP), and most of the existing studies mainly aim to provide effective models to satisfy the security requirements concerning a single blinded message. Unlike many previous works, the proposed scheme applies the signcryption paradigm to the proxy blind signature technology for handling multiple blinded messages at a time based on elliptic curve cryptography (ECC). This innovative method thus has a higher level of security to achieve the security goals of both blind signature and proxy signature. Moreover, the evaluation results show that this proposed protocol is more efficient, consuming low communication overhead while increasing the volume of digital messages compared to the performance from other solutions. Due to these features, this design is able to be implemented in small low-power intelligent devices and very suitable and easily adoptable for e-system applications in pervasive mobile computing environment.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.7
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• pp.693-700
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• 2016

It is important that we can calculate the order of non-supersingular elliptic curves with large prime factors over the finite field GF(q) to guarantee the security of public key cryptosystems based on discrete logarithm problem(DLP). Schoof algorithm, however, which is used to calculate the order of the non-supersingular elliptic curves currently is so complicated that many papers are appeared recently to update the algorithm. To avoid Schoof algorithm, in this paper, we propose an algorithm to calculate orders of elliptic curves over finite composite fields of the forms $GF(2^m)=GF(2^{rs})=GF((2^r)^s)$ using Weil's theorem. Implementing the program based on the proposed algorithm, we find a efficient non-supersingular elliptic curve over the finite composite field $GF(2^5)^{31})$ of the order larger than $10^{40}$ with prime factor larger than $10^{40}$ using the elliptic curve $E(GF(2^5))$ of the order 36.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.3
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• pp.477-487
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• 2017

Multiparty computation (MPC) is a computation technique where many participants provide their data and jointly compute operations to get a computation result. Earlier MPC protocols were mostly depended on communication between the users. Several schemes have been presented that mainly work by delegating operations to two non-colluding servers. Peter et al. propose a protocol that perfectly eliminates the need of users' participation during the whole computation process. However, the drawback of their scheme is the excessive dependence on the server communication. To cater this issue, we propose a protocol that reduce server communication overhead using the proxy re-encryption (PRE). Recently, some authors have put forward their efforts based on the PRE. However, these schemes do not achieve the desired goals and suffer from attacks that are based on the collusion between users and server. This paper, first presents a comprehensive analysis of the existing schemes and then proposes a secure and efficient MPC protocol. The proposed protocol completely eliminates the need of users' participation, incurs less communication overhead and does not need to solve the discrete logarithm problem (DLP) in order to get the computation results.