• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.69-75
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• 2011

In this paper, we analyze the key schedule of the block cipher SEED-192. According to the result of this paper, there exist weak keys in 16 out of 20 rounds of SEED-192 against the related-key rectangle/boomerang attack. This is the first cryptanalytic result for the key schedule of SEED-192.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.1
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• pp.25-32
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• 2009

KeeLoq is a very light block cipher with a 32-bit block and a 64-bit key. It is suitable for the wireless applications, and thus multiple automotive OEMs as Chrysler, GM, Honda, Toyota have used remote keyless entry systems and alarm systems in order to protect the their cars. In this paper, we introduce various weak-key classes that include $2^1{\sim}2^{32}$ keys and exploit the slide attack to propose key-recovery attacks under these weak-key classes.

• Journal of Communications and Networks
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• v.14 no.1
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• pp.104-110
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• 2012

Group key agreement protocols allow a group of users, communicating over a public network, to establish a shared secret key to achieve a cryptographic goal. Protocols based on certificateless public key cryptography (CL-PKC) are preferred since CL-PKC does not need certificates to guarantee the authenticity of public keys and does not suffer from key escrow of identity-based cryptography. Most previous certificateless group key agreement protocols deploy signature schemes to achieve authentication and do not have constant rounds. No security model has been presented for group key agreement protocols based on CL-PKC. This paper presents a security model for a certificateless group key agreement protocol and proposes a constant-round group key agreement protocol based on CL-PKC. The proposed protocol does not involve any signature scheme, which increases the efficiency of the protocol. It is formally proven that the proposed protocol provides strong AKE-security and tolerates up to $n$-2 malicious insiders for weak MA-security. The protocol also resists key control attack under a weak corruption model.

• The KIPS Transactions:PartC
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• v.11C no.3
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• pp.277-286
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• 2004

Password-based mechanism is widely used methods for user authentication. Password-based mechanisms are using memorable passwords(weak ferrets), therefore Password-based mechanism are vulnerable to the password guessing attack. To overcome this problem, man password-based authenticated key exchange protocols have been proposed to resist password guessing attacks. Recently, Seo-Sweeny proposed password-based Simple Authenticated Key Agreement(SAKA) protocol. In this paper, first, we will examine the SAKA and authenticated key agreement protocols, and then we will show that the proposed simple authenticated key agreement protocols are still insecure against Advanced Modification Attack. And we propose a password-based Simple Authenticated Key Agreement Protocol secure against Advanced Modification Attack.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1839-1848
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• 2012

Recently, smartphone communications using Wi-Fi channel are increasing rapidly to provide diverse internet services. The WPA security protocol was used for data protection between user and wireless AP. However, WPA-PSK protocol was known to be weak to the dictionary attack. In this paper, we proposed a secure WPA-PSK protocol to resist the dictionary attack. Since the proposed method was designed to generate a strong encryption key which is combined the Diffie-Hellman key agreement scheme with secrecy property of PSK(Pre-Shared Key), we can protect the Wi-Fi channel from Man-In-The-Middle attack and Rogue AP impersonation attack.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.1
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• pp.33-42
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• 2002

We present a systematic way to armor a zero-knowledge interactive proof based identification scheme that has badly chosen keys. Keys are sometimes mistakenly chosen to be weak(neither random nor long), and a weak key is often preferred to a strong key so that it might be easy for human to remember. Weak keys severely degrade the security of ZKIP based identification schemes. We show using off-line guessing attack how the weak key threats the security of ZlKIP based identification schemes. For the proper usage of ZKIP, we introduce a specialized form of ZKIP, which has a secret coin-tossing stage. Using the secret coin tossing, a secure framework is proposed for ZKIP based identification schemes with weak key in the ideal cipher model. The framework is very useful in password based authentication and key exchange protocol

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.9
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• pp.883-892
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• 1991

In this thesis explanation of new knapsack algorithm for public key system difficulty test and parallel architecture for implementation are suggested. Past Merkle-Hellman’s knapsack is weak in Shamir or Brickell`s attack by the effects of mapping into other easy sequenoes. But linearly shift knapsack system compensates them.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.4
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• pp.141-146
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• 2015

Data have been increased enormously due to the development of IT technology such as recent smart equipments, social network services and streaming services. To meet these environments the technologies that can treat mass data have received attention, and the typical one is Hadoop. Hadoop is on the basis of open source, and it has been designed to be used at general purpose computers on the basis of Linux. To initial Hadoop nearly no security was introduced, but as the number of users increased data that need security increased and there appeared new version that introduced Kerberos and Token system in 2009. But in this method there was a problem that only one secret key can be used and access permission to blocks cannot be authenticated to each user, and there were weak points that replay attack and spoofing attack were possible. Hence, to supplement these weak points and to maintain efficiency a protocol on the basis of group key, in which users are authenticated in logical group and then this is reflected to token, is proposed in this paper. The result shows that it has solved the weak points and there is no big overhead in terms of efficiency.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.678-682
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• 2005

IETF suggested AAA for safe and reliable user authentication on various network and protocol caused by development in internet and increase in users. Diameter standard authentication system does not provide mutual authentication and non-repudiation. AAA authentication system using public key was suggested to supplement such Diameter authentication but application in mobile service control nodes is difficult due to overhead of communication and arithmetic. ID based AAA authentication system was suggested to overcome such weak point but it still has the weak point against collusion attack or forgery attack. In this thesis, new ID based AAA authentication system is suggested which is safe against collusion attack and forgery attack and reduces arithmetic quantity of mobile nodes with insufficient arithmetic and power performance. In this thesis, cryptological safety and arithmetical efficiency is tested to test the suggested system through comparison and assessment of current systems. Suggested system uses two random numbers to provide stability at authentication of mobile nodes. Also, in terms of power, it provides the advantage of seamless service by reducing authentication executing time by the performance of server through improving efficiency with reduced arithmetic at nodes.

• Bulletin of the Korean Mathematical Society
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• v.46 no.4
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• pp.721-741
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• 2009

Consider RSA with N = pq, q < p < 2q, public encryption exponent e and private decryption exponent d. We first study cryptanalysis of RSA when certain amount of the Most Significant Bits (MSBs) or Least Significant Bits (LSBs) of d is known. The basic lattice based technique is similar to that of Ernst et al. in Eurocrypt 2005. However, our idea of guessing a few MSBs of the secret prime p substantially reduces the requirement of MSBs or LSBs of d for the key exposure attack. Further, we consider the RSA variant proposed by Sun and Yang in PKC 2005 and show that the partial key exposure attack works significantly on this variant.