• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.49-56
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• 2013

Among U-healthcare services adapting the latest IT technique and medical technique, a body-injecting device technique providing medical service to a patient who has incurable disease. But the body-injecting device technique can be easily exposed during wireless section to the third person and it can be used illegally. This paper proposes certification protocol which certifies a patient and hospital staff using random number created by certification server and a patient with hospital staff by synchronization. Specially, the proposed protocol uses security information created by information registered in certification server previously by a patient and hospital staff so that in keeps from accessing of third person who didn't get approval. And it gives more stability.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.3
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• pp.145-153
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• 2004

Digital fingerprinting schemes are cryptographic methods that a seller can identify a traitor who illegally redistributed digital contents by embedding it into buyer's information. Recently, Josep Domingo-Ferrer suggested an anonymous digital fingerprinting scheme based on committed oblivious transfer protocol. It is significant in the sense that it is completely specified from a computation point of view and is thus readily implementable. But this scheme has the serious problem that it cannot provide the security of buyers. In this paper, we first show how to break the existing committed oblivious transfer-based fingerprinting schemes and then suggest secure fingerprinting scheme by introducing oblivious transfer protocol with two-lock cryptosystem based on discrete logarithm. All computations are performed efficiently and the security degree is strengthened in our proposal.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.3
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• pp.109-114
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• 2005

On the research for constructing secure group-oriented proxy signature schemes, there are several proposals of threshold proxy signature schemes which combine the notions of proxy signature with threshold signature. Recently, Hsu and Wu proposed a threshold proxy signature scheme which uses a self-certified public key based on discrete logarithm problem. In this paper, we show that this scheme is vulnerable to original signer's forgery attack. So our attack provides the evidence that this scheme does not satisfy nonrepudiation property.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.3
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• pp.69-76
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• 2000

In this paper we propose a new group key renewal scheme suitable for secure mobile communications in which all members of the group can re-share the new group common key excepted a revoked member using a key distribution center(a trusted center). A renewal group key in the proposed scheme can be shared many times using pre-distributed data by a smart card without a preparation stage. This scheme is also avaliable for a large group network because the transmitted data amount after identifying the revoked member does not depend on a size of group. The secuirty of this scheme is based on the difficulty of the discrete logarithm problem.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.1
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• pp.3-10
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• 2002

This paper proposes an ID-based entity-aunthentication and authenticated key exchange protocol with ECC via two-pass communications between two parties who airs registered to the trusted third-party KC in advance. The proposed protocol developed by applying ECDSA and Diffie-Hellman key exchange scheme to the ID-based key distribution scheme over ECC proposed by H. Sakazaki, E. Okamoto and M. Mambo(SOM scheme). The security of this protocol is based on the Elliptic Curve Discrete Logarithm Problem(ECDLP) and the Elliptic Curve Diffie-Hellman Problem(ECDHP). It is strong against unknown key share attack and it provides the perfect forward secrecy, which makes up for the weakness in SOM scheme,

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.107-113
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• 2009

This paper considers the influence of floc on the sedimentation rate for the cohesive material. The effects of floc density and size changes were also taking into consideration during the experiment. The settling velocity of a discrete floc was measured in a quiescent water column. Floc diameter and density were investigated using a modified Stokes equation with some constants such as water density, viscosity, material density and the floc fractal dimension $n_f$ obtained from the relationship between the floc diameter and the floc settling. The floc diameter of quartz and alumina increased at increasing initial concentrations. The floc size of quartz with increasing NaCl concentration varied between approximately 0.8 um to $10{\mu}m$. Floc density decreased as floc size increased. The floc settling velocity and the floc diameter have a straight line relationship on a logarithm. The floc fractal dimension nf was 2.65 with increasing of initial concentration and 2.93 with increasing of NaCl. The exponent n to predict the settling velocity was proposed and varied from 1 to 1.93.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.3045-3052
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• 2010

The international standard signature algorithm DSA has been guaranteed its security based on discrete logarithm problem. Recently, the DSA was known to be vulnerable to some fault analysis attacks in which the secret key stored inside of the device can be extracted by occurring some faults when the device performs signature algorithm. After analyzing an existing fault attack presented by Bao et al., this paper proposed a new fault analysis attack by disturbing the random number. Furthermore, we presented a countermeasure to compute DSA signature that has its immunity in the two types of fault attacks. The security and efficiency of the proposed countermeasure were verified by computer simulations.

• The Journal of the Korea Contents Association
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• v.3 no.3
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• pp.40-46
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• 2003

In the paper, designed digital contents security module to check unlawfulness reproduction and distribution of digital contents. This paper applied Diffie-Hellman algorithm that use discrete logarithm and random number as primary for public key application to create encryption key that agree each other through communication channel between DCPS and HOST, and applied Triple DES repeat DES 3 times through 2 different encryption key that is selecting ANSI X9.17 that is key management standard, ISO 8732 and PEM(Privacy-Enhanced Mail) etc. by secondary protection for safe transmission of digital contents in transmission line. Designed security module consist of key exchange module, key derivation module and copy protection processing module. Digital contents security module that design in this thesis checks reproduction and distribution of digital contents by unauthenticated user through user certification function and digital contents encryption function, and protect digital contents transmission line.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1C
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• pp.14-21
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• 2011

Cryptographic protocols based on bilinear pairings provide excellent alternatives to conventional elliptic curve cryptosystems based on discrete logarithm problems. Through active research has been done toward fast computation of the bilinear pairings, it is still believed that the computational cost of one pairing computation is heavier than the cost of one ECC scalar multiplication. However, there have been many progresses in pairing computations over binary fields. In this paper, we compare the cost of BLS signature scheme with ECDSA with equvalent level of security parameters. Analysis shows that the cost of the pairing computation is quite comparable to the cost of ECC scalar multiplication for the case of binary fields.

• 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.