• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.445-453
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• 2010

Because of heavy computational overheads, the use of public key cryptosystem in Wireless Sensor Networks seems unfeasible. But some recent researches show that certain public key cryptosystem can be used in WSN, in which the key and data size, power consumption is relatively small. The NTRU cryptosystem is suggested as one of the candidates of public key cryptosystems which can be used in wireless sensor networks. In this paper, we propose an efficient key agreement scheme using NTRU and we show that it can be used in wireless sensor networks.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.6
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• pp.313-319
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• 2019

Finite field operations have played an important role in error correcting codes and cryptosystems. Recently, the necessity of efficient computation processing is increasing for security in cyber physics systems. Therefore, efficient implementation of finite field arithmetics is more urgently needed. These operations include addition, multiplication, division and inversion. Addition is very simple and can be implemented with XOR operation. The others are somewhat more complicated than addition. Among these operations, multiplication is the most important, since time-consuming operations, such as exponentiation, division, and computing multiplicative inverse, can be performed through iterative multiplications. In this paper, we propose a multiplexer based parallel computation algorithm that performs Montgomery multiplication over finite field using redundant basis. Then we propose an efficient multiplexer based semi-systolic multiplier over finite field using redundant basis. The proposed multiplier has less area-time (AT) complexity than related multipliers. In detail, the AT complexity of the proposed multiplier is improved by approximately 19% and 65% compared to the multipliers of Kim-Han and Choi-Lee, respectively. Therefore, our multiplier is suitable for VLSI implementation and can be easily applied as the basic building block for various applications.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.1
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• pp.90-96
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• 2011

In this paper, we propose a new discrete logarithm problem(DLP) based on the class semigroups of imaginary quadratic non-maximal orders using the special character of non-invertible ideal and analysis its security. To do this, we first explain the mathematical background explicitly and prove some properties of Cls (O) which relate to constructing the DLP and guaranteeing the security. To test the security of the proposed DLP, we compare the class number of the maximal order with that of the non-maximal order and investigate the unique factorization problems of ideals between class groups of the maximal orders and class semigroups of non-maximal orders to ensure the security of the cryptosystem.

• Journal of the Korea Society of Computer and Information
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• v.8 no.4
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• pp.104-110
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• 2003

In this paper, we proposed hybrid cryptosystem of Diffie-Hellman base in Elliptic Curve, and explained for specific protocol design. The proposed system is efficient hybrid cryptosystems system that offer implicit key authentication about sender and receiver unlike existing hybrid system. This system increased safety generating session key using pseudo-random number generator by cryptographic. Because the system is hybrid system, it is more efficient in calculation amount aspect supplementing merit and fault of public key system and secret key system. Also, the system can not get right plaintext except receiver even if sender's secret key is revealed and impersonation attack is impossible. And the system offers security on known keys without influencing in safety of other session's cryptogram even if session key is exposed. And the system is provided safety about mutual entity authentication and replay attack.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.3421-3437
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• 2018

With the enlargement of wireless technology, vehicular ad-hoc networks (VANETs) are rising as a hopeful way to realize smart cities and address a lot of vital transportation problems such as road security, convenience, and efficiency. To achieve data confidentiality, integrity and authentication applying lightweight cryptosystems is widely recognized as a rather efficient approach for the VANETs. The Khudra cipher is such a lightweight cryptosystem with a typical Generalized Feistel Network, and supports 80-bit secret key. Up to now, little research of fault analysis has been devoted to attacking Khudra. On the basis of the single nibble-oriented fault model, we propose a differential fault analysis on Khudra. The attack can recover its 80-bit secret key by introducing only 2 faults. The results in this study will provides vital references for the security evaluations of other lightweight ciphers in the VANETs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.732-735
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• 2008

In order for fast calculation for the modular multiplication which plays an essential role in RSA cryptography algorithm, the Montgomery algorithm has been studed and developed in varous ways. Since there is no division operation in the algorithm, it is able to perform a fast modular multiplication. However, the Montgomery algorithm requires a few extra operations in the progress of which transformation from/to ordinary modular form to/from Montgomery form should be made. Concept of high radix operation can be considered by splitting the key size into word-defined units in the RSA cryptosystems which use longer than 1024 key bits. In this paper, We adopted the concept of operand scanning methods to enhance the traditional Montgomery algorithm. The methods consider issues of optimization, memory usage, and calculation time.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.7
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• pp.327-331
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• 2008

Optimal Extension Fields (OEFs) are finite fields of a special form which are very useful for software implementation of elliptic curve cryptosystems. Bailey and Paar introduced efficient OEF arithmetic algorithms including the $p^ith$ powering operation, and an efficient algorithm to construct OEFs for cryptographic use. In this paper, we give a counterexample where their $p^ith$ powering algorithm does not work, and show that their OEF construction algorithm is faulty, i.e., it may produce some non-OEFs as output. We present improved algorithms which correct these problems, and give improved statistics for the number of OEFs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.12
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• pp.2392-2402
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• 2011

In order to protect some important information communicated through an insecure network, a common hidden key must be used. One can produce the common hidden key using key agreement protocols; and this helps to have high security in modern data networks. Today, the designers of public key cryptography protocols try to set the public identity of a system's users (like their email addresses) as their public key. This not only makes a cryptographic protocol more efficient but also decreases its cost. These protocols are called "identity-based". In this article, an identity-based multiple key agreement scheme will be presented; this scheme uses the challenge-response method to do the verification. While the number of random values produced in our scheme is the same as other schemes, the number of keys generated in this scheme is much more than what many other key agreement schemes produce,. Therefore, we will have less computational complexities campered with other schems. In this paper, we consider the security of our scheme and consequently, we will show that it satisfies many security conditions such as strong security.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.826-845
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• 2017

Outsourcing computation is one of the most important applications in cloud computing, and it has a huge ability to satisfy the demand of data centers. Modular exponentiation computation, broadly used in the cryptographic protocols, has been recognized as one of the most time-consuming calculation operations in cryptosystems. Previously, modular exponentiations can be securely outsourced by using two untrusted cloud servers. In this paper, we present two practical and secure outsourcing modular exponentiations schemes that support only one untrusted cloud server. Explicitly, we make the base and the index blind by putting them into a matrix before send to the cloud server. Our schemes provide better performance in higher efficiency and flexible checkability which support single cloud server. Additionally, there exists another advantage of our schemes that the schemes are proved to be secure and effective without any cryptographic assumptions.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.4
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• pp.270-273
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• 2009

In 1988, Buchmann et al. proposed a public key cryptosystem making use of ideals of the maximal orders in quadra tic fields which may pave the way for a public key cryptosystem using imaginary quadratic non-invertible ideals as generators. Next year, H$\ddot{u}$hnlein, Tagaki et al. published the cryptosystem with trapdoor and conductor prime p over non-maximal orders. On the other hand Kim and Moon proposed a public key cryptosystrem and a key distribution cry ptotsystem over class semigroup in 2003. We, in this paper, introduce and analyze the cryptotsystems mentioned above.