• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2493-2500
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• 1997

We propose a new key management scheme for multiuser group which is classified as hierarchical structure (sometimes it is called a multilevel security hierarchy) in the symmetric key cryptosystem. The proposed scheme is based on the trapdoor one-way permutations which are generated by the pseudo-random permutation algorithm, and it is avaliable for multilevel hierarchical structure composed of a totally ordered set and a partially ordered set, since it has advantage for time and storage from an implemental point of view. Moreover, we obtain a performance analysis by comparing with the other scheme, and show that the proposed scheme is very efficient for computing time of key generation and memory size of key storage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.7
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• pp.575-597
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• 1991

As an elegant solution of the key management scheme for a conventional cryptosystem. Diffie and Hellman introduced a public key distrbution system, whose security depends on the intractabliity of discrete loganthm problem over a finite field, and since then a lot of vartants of DH KDSS have been proposed. In this paper, we present the systematic approach to analyzing the security of a generalized DH KDS and designing an efficient and secure scheme. We classify vanous attacking methods and point out a possible way to avoid these attacks through the examples of successful attacking methods and point out a possible way to avoid these attacks through the examples of successful attack against those systems proposed so far or designed for this purpose. As security analysis tools, we present the redueiblity test, the information theoretic approach, and the protocol analysis technique, which we apply to variations of DH scheme to examine their security under all possble attacks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.383-386
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• 2009

In this paper, we propose some parallel structures of the word-based nonlinear combine functions in word-based stream cipher, high-speed versions of general (bit-based) nonlinear combine functions. Especially, we propose the high-speed structures of popular three kinds in word-based nonlinear combiners using by PS-WFSR (Parallel-Shifting or Parallel-Structured Word-based FSR): m-parallel word-based nonlinear combiner without memory, m-parallel word-based nonlinear combiner with memories, and m-parallel word-based nonlinear filter function. Finally, we analyze its cryptographic security and performance.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.6
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• pp.1427-1437
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• 2018

While biometric authentication system has been in general use, research is ongoing to apply biometric data to public key infrastructure. It is a significant task to generate a cryptographic key from biometrics in setting up a public key of Bio-PKI. Methods for generating the key by quantization of feature vector can cause data loss and degrade the performance of key extraction. In this paper, we suggest a new method for generating a cryptographic key from classification results of biometric data using multiple classifying models. Our proposal does not cause data loss of feature vector so it showed better performance in key extraction. Also, it uses the multiple models to generate key blocks which produce sufficient length of the key.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.221-223
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• 2014

Power analysis attack on cryptographic hardware device aims to study the power consumption while performing operations using secrets keys. Power analysis is a form of side channel attack which allow an attacker to compute the key encryption from algorithm using Simple Power Analysis (SPA), Differential Power Analysis (DPA) or Correlation Power Analysis (CPA). The theoretical weaknesses in algorithms or leaked informations from physical implementation of a cryptosystem are usually used to break the system. This paper describes how power analysis work and we provide an overview of countermeasures against power analysis attacks.

• Journal of IKEEE
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• v.23 no.1
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• pp.200-206
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• 2019

Recently, there is a growing preference for a fast and secure cryptographic protocol that is applicable to Internet of things environments. Among the lattice-based cryptographic algorithms, the NTRU cryptosystem is secure by virtue of the shortest vector problem (SVP) and the closest problem(CVP), which is a problem of finding very short vectors and closest vector. NTRUSign, an electronic signature based on this cryptographic algorithm, has been proposed and proved unsafe for script attacks. In this paper, we propose a security protocol using a symmetric key algorithm by securing a shared key using key exchange. Therefore, the attacker can not compute the key value and intends to propose a more secure digital signature.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.5
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• pp.113-127
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• 2003

WTLS as secure protocol of WAP makes TLS that is used in wireless Intemet protocol for TCP security be appropriate for wireless environments. And purpose of WTLS is to provide safe and efficient services. WTLS protocol consists of 4 protocols(Handshake, ChangeCipherSpec, Alert, Application Data etc.). In this papers we analyze properties of Handshake protocol and procedures of establishing master secret in detail. And then we analyze securities against several attacker models with them for a basis. Also we propose new Handshake protocol that is secure against active attacker model and can provide various security services.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.1
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• pp.47-57
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• 2004

The Goldreich-Goldwasser-Halevi(GGH)'s signature scheme from Crypto '97 is cryptanalyzed, which is based on the well-blown lattice problem. We mount a chosen message attack on the signature scheme, and show the signature scheme is vulnerable to the attack. We collects n lattice points that are linearly independent each other, and constructs a new basis that generates a sub-lattice of the original lattice. The sub-lattice is shown to be sufficient to generate a valid signature. Empirical results are presented to show the effectiveness of the attack Finally, we show that the cube-like parameter used for the private-key generation is harmful to the security of the scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.5
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• pp.153-164
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• 2004

Under a large-scale client-server service environment, e.g., online games, encrypting data for acquiring information security often causes overload to the server and hence degradation of the service itself. Therefore, for reducing encryption payload, it is necessary to use adequately an efficient encryption scheme with respect to the security requirements of transmission data. In this paper, we propose a packet encryption scheme using multiple cryptosystems to realize such capability, which assigns a different cryptosystem according to the security requirements level. The proposed encryption scheme is applicable to internet services with heavy traffic ratios in which different kinds of data packets are incessantly transmitted between clients and servers. To show its effectiveness and superiority, the performance of the proposed encryption scheme is verified by experiments.

• 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.