• 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.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.1859-1862
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• 2003

Security of digital images attracts much attention recently, and many image encryption methods have been proposed. This paper proposed an image encryption methodology to hide the image information. The target data of it is the result from quantization in the wavelet domain. This method encrypts only part of the image data rather than the whole data of the original image. For ciphering the quantization index we use a novel image encryption Algorithm called BRIE(Bit Recirculation Image Encryption). which was proposed by J. C. Yen and J. I. Guo in 1999. According to a chaotic binary sequence generated by BRIE, the block which is produced by quantization index is cyclically shifted in the right or left direction. Finally, simulation results are included to demonstrate its effectiveness.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.3
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• pp.43-51
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• 2017

MANET consists of only wireless nodes having limited processing capability. It processes routing and data transmission through cooperation among each other. And it is exposed to many attack threats due to the dynamic topology by movement of nodes and multi-hop communication. Therefore, the reliability of transmitted data between nodes must be improved and security of integrity must be high. In this paper, we propose a method to increase the reliability of transmitted data by providing a secure cryptography protocol. The proposed method used a hierarchical structure to provide smooth cryptographic services. The cluster authentication node issues the cluster authentication key pair and unique key to the nodes. The nodes performs the encryption through two steps of encryption using cluster public key and block encryption using unique key. Because of this, the robustness against data forgery attacks was heightened. The superior performance of the proposed method can be confirmed through comparative experiment with the existing security routing method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1790-1806
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• 2016

Digital image encryption is widely used for image data security. JPEG standard compresses image with great performance on reducing file size. Thus, to encrypt an image in JPEG format we should keep the quality of original image and reduced size. This paper proposes a JPEG image encryption scheme based on quantized DC and non-zero AC coefficients inner category scrambling. Instead of coefficient value encryption, the address of coefficient is encrypted to get the address of cipher text. Then 8*8 blocks are shuffled. Chaotic iteration is employed to generate chaotic sequences for address scrambling and block shuffling. Analysis of simulation shows the proposed scheme is resistant to common attacks. Moreover, the proposed method keeps the file size of the encrypted image in an acceptable range compared with the plain text. To enlarge the cipher text possible space and improve the resistance to sophisticated attacks, several additional procedures are further developed. Contrast experiments verify these procedures can refine the proposed scheme and achieve significant improvements.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.269-272
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• 2005

For the efficient image encryption, we proposed the encryption algorithm using the chaotic function and elementary matrix operation defined on the bit plane decomposition. Though the chaotic encryption algorithm is faster than block encryption, it uses a real number computation. In this sense, we use the row and column operations on the bit-plane decomposed images combined with logistic function for the recursive rounding number, too.

• Journal of Korea Multimedia Society
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• v.11 no.8
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• pp.1093-1100
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• 2008

Feistel and SPN are the two main structures in designing a block cipher algorithm. Unlike Feistel, an SPN has an asymmetric structure in encryption and decryption. In this paper we propose an SPN algorithm which has a symmetric structure in encryption and decryption. The whole operations in our SPN algorithm are composed of the even numbers of N rounds where the first half of them, 1 to N/2, applies function and the last half of them, (N+1)/2 to N, employs inverse function. Symmetry layer is executed to create a symmetry block in between function layer and inverse function layer. AES encryption and decryption algorithm, whose safety is already proved, are exploited for function and inverse function, respectively. In order to be secure enough against the byte or word unit-based attacks, 32bit rotation and simple logical operations are performed in symmetry layer. Due to the simplicity of the proposed encryption and decryption algorithm in hardware configuration, the proposed algorithm is believed to construct a safe and efficient cipher in Smart Card and RFID environments where electronic chips are built in.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.11
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• pp.2031-2038
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• 2008

A small-area and high-speed authentication/security processor (WUSB_Sec) IP is designed, which performs the 4-way handshake protocol for authentication between host and device, and data encryption/decryption of wireless USB system. The PRF-256 and PRF-64 are implemented by CCM (Counter mode with CBC-MAC) operation, and the CCM is designed with two AES (Advanced Encryption Standard) encryption coles working concurrently for parallel processing of CBC mode and CTR mode operations. The AES core that is an essential block of the WUSB_Sec processor is designed by applying composite field arithmetic on AF$(((2^2)^2)^2)$. Also, S-Box sharing between SubByte block and key scheduler block reduces the gate count by 10%. The designed WUSB_Sec processor has 25,000 gates and the estimated throughput rate is about 480Mbps at 120MHz clock frequency.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.165-168
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• 2000

A hardware architecture to implement the SEED block cipher algorithm into one chip is described. Each functional unit is designed with VHDL hardware description language and synthesis tools. The designed hardware receives a 128-bit block of plain text input and a 128-bit key, and generates a 128-bit cipher block after 16-round operations after 8 clocks. The encryption time is within 20 nsec.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.860-868
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• 2011

Feistel and SPN are the two main structures in a block cipher. Feistel is a symmetric structure which has the same structure in encryption and decryption, but SPN is not a symmetric structure. In this paper, we propose a SPN block cipher so called SSB which has a symmetric structure in encryption and decryption. The proposed SSB is composed of the even numbers of N rounds. Each round consists of a round key addition layer, a subsitution layer, a byte exchange layer and a diffusion layer. The subsitution layer of the odd round is inverse function of one of the even round. And the diffusion layer is a MDS involution matrix. The differential and linear attack probability of SSB is $2^{-306}$ which is same with AES. The proposed symmetric SPN block cipher SSB is believed to construct a safe and efficient cipher in Smart Card and RFID environments which is in limited hardware and software resources.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1276-1284
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• 2017

Lightweight Encryption Algorithm (LEA) that was standardized as a lightweight block cipher was implemented with 8-bit data path, and the vulnerability of LEA encryption processor to correlation power analysis (CPA) attack was analyzed. The CPA used in this paper detects correct round keys by analyzing correlation coefficient between the Hamming distance of the computed data by applying hypothesized keys and the power dissipated in LEA crypto-processor. As a result of CPA attack, correct round keys were detected, which have maximum correlation coefficients of 0.6937, 0.5507, and this experimental result shows that block cipher LEA is vulnerable to power analysis attacks. A masking method based on TRNG was proposed as a countermeasure to CPA attack. By applying masking method that adds random values obtained from TRNG to the intermediate data of encryption, incorrect round keys having maximum correlation coefficients of 0.1293, 0.1190 were analyzed. It means that the proposed masking method is an effective countermeasure to CPA attack.