• Journal of KIISE:Information Networking
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• v.29 no.5
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• pp.473-481
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• 2002

Decryption of encrypted malicious scripts is essential in order to analyze the scripts and to determine whether they are malicious. An effective decryption technique is one that is designed to consider the characteristics of the script languages rather than the specific encryption patterns. However, currently X-raying and emulation are not the proper techniques for the script because they were designed to decrypt binary malicious codes. In addition to that, heuristic techniques are unable to decrypt unknown script codes that use unknown encryption techniques. In this paper, we propose a new technique that will be able to decrypt malicious scripts based on analytical approach. we describe its implementation.

• International Journal of Contents
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• v.11 no.4
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• pp.56-69
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• 2015

This paper proposes an efficient image encryption scheme based on quintuple encryption using two chaotic maps. The encryption process is realized with quintuple encryption by calling the encrypt(E) and decrypt(D) functions five times with five different keys in the form EDEEE. The decryption process is accomplished in the reverse direction by invoking the encrypt and decrypt functions in the form DDDED. The keys for the quintuple encryption/decryption processes are generated by using a Tent map. The chaotic values for the encrypt/decrypt operations are generated by using a Gumowski-Mira map. The encrypt function E is composed of three stages: permutation, pixel value rotation and diffusion. The permutation stage scrambles all the rows and columns to chaotically generated positions. This stage reduces the correlation radically among the neighboring pixels. The pixel value rotation stage circularly rotates all the pixels either left or right, and the amount of rotation is based on chaotic values. The last stage performs the diffusion four times by scanning the image in four different directions: Horizontally, Vertically, Principal diagonally and Secondary diagonally. Each of the four diffusion steps performs the diffusion in two directions (forward and backward) with two previously diffused pixels and two chaotic values. This stage ensures the resistance against the differential attacks. The security and performance of the proposed method is investigated thoroughly by using key space, statistical, differential, entropy and performance analysis. The experimental results confirm that the proposed scheme is computationally fast with security intact.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.724-737
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• 2020

Corrected Block TEA(or XXTEA) is a block cipher designed to correct security weakness in the original block TEA in 1998. In this paper, XXTEA cipher hardware which can encrypt or decrypt between 64-bit and 256-bit messages using 128-bit master key is implemented. Minimum message block size is 64-bit wide and maximal message block size is 256-bit wide. The designed XXTEA can encrypt and decrypt variable-length message blocks which are some arbitrary multiple of 32 bits in message block sizes. XXTEA core of this paper is described using Verilog-HDL and downloaded on Vertex4. The operation frequency is 177MHz. The maximum throughput for 64-bit message blocks is 174Mbps and that of 256-bit message blocks is 467Mbps. The cryptographic IP of this paper is applicable as security module of the mobile areas such as smart card, internet banking, e-commerce and IoT.

• Journal of information and communication convergence engineering
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• v.10 no.1
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• pp.53-60
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• 2012

Attribute-based encryption (ABE) is an encryption scheme in which the user is able to decrypt a ciphertext with associated attributes. However, the scheme does not offer the capability of decryption to others when the user is offline. For this reason, the attribute-based proxy re-encryption (ABPRE) scheme was proposed, which combines traditional proxy re-encryption with ABE, so a user is able to empower designated users to decrypt the re-encrypted ciphertext with the associated attributes of designated users. However, previous ABPRE schemes demands a number of pairing operations that imply huge computational overhead. To reduce the number of pairing operations, we reduce the pairing operations with exponent operations. This paper provides a novel approach to an ABPRE scheme with constant pairing operation latency.

• Journal of the Korea Society of Computer and Information
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• v.24 no.7
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• pp.87-91
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• 2019

In the IoT(Internet of Things) environment, various devices are utilized and applied for different sites. But attackers can access easy to IoT systems, and try to operate DDoS(Distributed Denial-of-Service) attacks. In this paper, Sensor nodes, Cluster heads, and Gateways operates lightweight mutual authentication each others. Since authenticated sensor nodes and cluster heads only send transactions to Gateways, proposed techniques prevent DDoS attacks. In addition, the blockchain system contains secure keys to decrypt data from sensor nodes. Therefore, attackers can not decrypt the data even if the data is eavesdropped.

• Journal of Multimedia Information System
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• v.2 no.2
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• pp.193-206
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• 2015

In this paper a new approach for image encryption based on quadruple encryption with dual chaotic maps is proposed. The encryption process is performed with quadruple encryption by invoking the encrypt and decrypt routines with different keys in the sequence EDEE. The decryption process is performed in the reverse direction DDED. The key generation for the quadruple encryption is achieved with a 1D Circle map. The chaotic values for the encrypt and decrypt routines are generated by using a 2D Henon map. The Encrypt routine E is composed of three stages i.e. permutation, pixel value rotation and diffusion. The permutation is achieved by: row and column scrambling with chaotic values, exchanging the lower and the upper principal and secondary diagonal elements based on the chaotic values. The second stage circularly rotates all the pixel values based on the chaotic values. The last stage performs the diffusion in two directions (forward and backward) with two previously diffused pixels and two chaotic values. The security and performance of the proposed scheme are assessed thoroughly by using the key space, statistical, differential, entropy and performance analysis. The proposed scheme is computationally fast with security intact.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.240-246
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• 2008

This paper propose a method to enhance the performance of digital contents streaming services with the improve DRM system by maximizing the distribute computing performance and minimizing the overheads of security threatens caused by increasing users and sharing contents in P2P environments. By improving authentication protocols and license protocols to perform decryption and execution simultaneously by only download of the license, streaming services are more enhanced rather than existing DRM systems. For evaluate the performance, this paper compared execution time of existing DRM systems which decrypt the encrypted data file before execute with improved DRM system which execute and decrypt the encrypted data file simultaneously. In experiment, improved DRM system can maintain steady bandwidth and reduce the execution time in compare to existing DRM systems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.1
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• pp.17-27
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• 2020

Many users are using password managers in order to conveniently manage several usernames and passwords needed to access the web sites. The password manager encrypts and stores several passwords on the server, and the user accesses the server to receive the password information. Thus, if an attacker can sniff a message between the password manager and the server and decrypt the message content, or if an attacker can steal the computer's memory and decrypt the message content, then all the passwords will be exposed to the attacker. In this paper, we analyze the client-server communications and encryption process of password mangers and show there is a serious vulnerability in memory attack.

• The KIPS Transactions:PartC
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• v.10C no.7
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• pp.929-936
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• 2003

We Propose the Suity Cryptography File System to encrypt or decrypt a plaintext or an encrypted tort by using the dynamic linking mechanism In the Linux kernel. The dynamic linking mechanism gives the flexibility of the kernel without changing the kernel. The Sorority Cryptography File System uses the blowfish algorithm to encrypt or decrypt a data. To overcome the overhead of the key server, I use key generating algorithm which is installed in the same Security Cryptography File System. The Security Cryptography file System is fitted into the Linux system.

• ETRI Journal
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• v.27 no.1
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• pp.114-117
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• 2005

In this paper, we propose a key management scheme which can provide delivery of the key used to encrypt a digital content from the package server to digital rights management (DRM) clients in a secure manner. The proposed scheme can protect digital content from attacks since an encrypted digital content is sent by a package server and only DRM clients can decrypt the encrypted digital content. It protects the key not only from purchasers but also among the other principals who manage the distribution and license servers.