• Convergence Security Journal
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• v.6 no.1
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• pp.75-82
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• 2006

This paper proposes CPR(Computer-based patient record) system that is utilized in Ubiquitous environment, establish security policy by analyzing security limitation of system and design suitable security system in CPR system. The present study designed a CPR system and, for the development of a security system, established security policies for the CPR system through analyzing the operating environment and vulnerability in security and designed a security system implementing the policies. The security system supporting CPR system is composed of authentication system, XML documentation and encryption of medical information and network security system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.4
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• pp.1516-1528
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• 2015

We introduce attribute set based signature (ASBS), a new cryptographic primitive which organizes user attributes into a recursive set based structure such that dynamic constraints can be imposed on how those attributes may be combined to satisfy a signing policy. Compared with attribute based signature (ABS), ASBS is more flexible and efficient in managing user attributes and specifying signing policies. We present a practical construction of ASBS and prove its security in the standard model under three subgroup decision related assumptions. Its efficiency is comparable to that of the most efficient ABS scheme.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.113-119
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• 2003

Both the highly developed computing environment and the rapid increase of the internet users enable the present web based cluster system accounting service to help many users access to numerous data at high speed. However, the information security of users and data is also as important as the convenience of the systematic environment. Especially, the significance of damage to the individuals and organizations resulted from the data outflow, hacking and malicious coding has risen up to one of the most essential problems in the internet service business. In this study, I suggest a more safe web based cluster system accounting service solution applying SEED, the Korean Telecommunications Technology Association (TTA) standard encryption algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.229-231
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• 2001

IPSec is a security protocol suite that provides encryption and authentication services for IP messages at the network layer of the Internet. Key recovery has been the subject of a lot of discussion, of much controversy and of extensive research. Key recovery, however, might be needed at a corporate level, as a from of key management. The basic observation of the present paper is that cryptographic solutions that have been proposed so far completely ignore the communication context. Static systems are put forward fur key recovery at network layer and solutions that require connections with a server are proposed at application layer. We propose example to provide key recovery capability by adding key recovery information to an IP datagram. It is possible to take advantage of the communication environment in order to design key recovery protocols that are better suited and more efficient.

• ETRI Journal
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• v.39 no.1
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• pp.108-115
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• 2017

ARIA is a 128-bit block cipher that has been selected as a Korean encryption standard. Similar to AES, it is robust against differential cryptanalysis and linear cryptanalysis. In this study, we analyze the security of ARIA against differential-linear cryptanalysis. We present five rounds of differential-linear distinguishers for ARIA, which can distinguish five rounds of ARIA from random permutations using only 284.8 chosen plaintexts. Moreover, we develop differential-linear attacks based on six rounds of ARIA-128 and seven rounds of ARIA-256. This is the first multidimensional differential-linear cryptanalysis of ARIA and it has lower data complexity than all previous results. This is a preliminary study and further research may obtain better results in the future.

• ETRI Journal
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• v.34 no.3
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• pp.421-428
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• 2012

An aggregate signature scheme is a digital signature scheme that allows aggregation of n distinct signatures by n distinct users on n distinct messages. In this paper, we present an aggregate signcryption scheme (ASC) that is useful for reducing the size of certification chains (by aggregating all signatures in the chain) and for reducing message size in secure routing protocols. The new ASC scheme combines identity-based encryption and the aggregation of signatures in a practical way that can simultaneously satisfy the security requirements for confidentiality and authentication. We formally prove the security of the new scheme in a random oracle model with respect to security properties IND-CCA2, AUTH-CMA2, and EUF-CMA.

• The Journal of the Korea Contents Association
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• v.6 no.6
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• pp.56-63
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• 2006

Key recovery has been the subject of a lot of discussion, of much controversy and of extensive research. Key recovery, however, might be needed at a corporate level, as a form of key management. The basic observation of the present paper is that cryptographic solutions that have been proposed so far completely ignore the communication context. IPSec is a security protocol suite that provides encryption and authentication services for IP messages at the network layer of the Internet. We propose example to provide key recovery capability by adding key recovery information to an IP datagram. It is possible to take advantage of the communication environment in order to design key recovery protocols that are better suited and more efficient.

• International Journal of Computer Science & Network Security
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• v.21 no.12spc
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• pp.451-458
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• 2021

Providing a secure and effective way to protect confidential and private data is an urgent process, and accordingly, we will present in this research paper a new method, which is called multiple rounds variable block method (MRVB) which depends on the use of a colored image that is kept secret to generate needed work and round keys. This method can be used to encrypt-decrypt data using various lengths private key and data blocks with various sizes. The number of rounds also will be variable starting from one round. MRVB will be implemented and compared with the encryption-decryption standards DES and AES to show the improvements provided by the proposed method in increasing the security level and in increasing the throughput of the process of data cryptography. The generated private key contents will depend on the used image_key and on the selected number of rounds and the selected number of bytes in each block of data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1163-1170
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• 2016

A hardware implementation of ultra-lightweight block cipher algorithm PRESENT which was specified as a standard for lightweight cryptography ISO/IEC 29192-2 is described. The PRESENT crypto-processor supports two key lengths of 80 and 128 bits, as well as four modes of operation including ECB, CBC, OFB, and CTR. The PRESENT crypto-processor has on-the-fly key scheduler with master key register, and it can process consecutive blocks of plaintext/ciphertext without reloading master key. In order to achieve a lightweight implementation, the key scheduler was optimized to share circuits for key lengths of 80 bits and 128 bits. The round block was designed with a data-path of 64 bits, so that one round transformation for encryption/decryption is processed in a clock cycle. The PRESENT crypto-processor was verified using Virtex5 FPGA device. The crypto-processor that was synthesized using a $0.18{\mu}m$ CMOS cell library has 8,100 gate equivalents(GE), and the estimated throughput is about 908 Mbps with a maximum operating clock frequency of 454 MHz.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.1
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• pp.47-57
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• 2003

In this paper, we firstly evaluate the resistance of the reduced 5-round version of the block cipher CIKS-1 against linear cryptanalysis(LC) and show that we can attack full-round CIKS-1 with \ulcorner56-bit key through the canonical extension of our attack. A feature of the CIKS-1 is the use of both Data-Dependent permutations(DDP) and internal key scheduling which consist in data dependent transformation of the round subkeys. Taking into accout the structure of CIKS-1 we investigate linear approximation. That is, we consider 16 linear approximations with p=3/4 for 16 parallel modulo $2^2$ additions to construct one-round linear approximation and derive one-round linear approximation with the probability P=1/2+$2^{-17}$ by Piling-up lemma. Then we present 3-round linear approximation with 1/2+$2^{-17}$ using this one-round approximation and attack the reduced 5-round CIKS-1 with 64-bit block by LC. In conclusion we present that our attack requires $2^{38}$chosen plaintexts with a probability of success of 99.9% and about $2^{67-7}$encryption times to recover the last round key.(But, for the full-round CIKS-1, our attack requires about $2^{166}$encryption times)