• Proceedings of the Korea Multimedia Society Conference
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• 2002.05d
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• pp.955-958
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• 2002

암호화를 위한 블록간의 연산 모드에서 어떤 연산 모드를 사용하는가에 따라 평문, 암호문 또는 키 추측 등에 많은 영향을 주게 된다. 본 논문에서는 여러 가지 블록 암호 연산 모드에 대해 알아보고, 다음 블록에 대한 키 정보의 암호화 강도를 효율적으로 높일 수 있는 RFB(Round key FeedBack) 운영 모드를 제안한다.

• Journal of KIISE
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• v.43 no.8
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• pp.933-945
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• 2016

Sharing data by multiple users on the public storage, e.g., the cloud, is considered to be efficient because the cloud provides on-demand computing service at anytime and anywhere. Secure data sharing is achieved by fine-grained access control. Existing symmetric and public key encryption schemes are not suitable for secure data sharing because they support 1-to-1 relationship between a ciphertext and a secret key. Attribute based encryption supports fine-grained access control, however it incurs linearly increasing ciphertexts as the number of attributes increases. Additionally, the decryption process has high computational cost so that it is not applicable in case of resource-constrained environments. In this study, we propose an efficient attribute-based secure data sharing scheme with outsourceable decryption. The proposed scheme guarantees constant-size ciphertexts irrespective of the number of attributes. In case of static attributes, the computation cost to the user is reduced by delegating approximately 95.3% of decryption operations to the more powerful storage systems, whereas 72.3% of decryption operations are outsourced in terms of dynamic attributes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.339-340
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• 2018

본 논문에서는 경량 블록암호 알고리듬 TWINE의 하드웨어 설계에 대해 기술한다. TWINE은 80-비트 또는 128-비트의 마스터키를 사용하여 64-비트의 평문(암호문)을 암호(복호)하여 64-비트의 암호문(평문)을 만드는 대칭키 블록암호이며, s-box와 XOR만 사용하므로 경량 하드웨어 구현에 적합하다는 특징을 갖는다. 암호화 연산과 복호화 연산의 하드웨어 공유를 통해 게이트 수가 최소화 되도록 구현하였으며, 설계된 TWINE 크립토 코어는 RTL 시뮬레이션을 통해 기능을 검증하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.333-337
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• 2006

Symmetric block ciper algorithm consists of a chains of operations such as permutation and substitution. There exists four kinds of operation mode, CBC, ECB, CFB, and OFB depending on the operation paradigm. Since the final ciper text is obtained through the many rounds of operations, it consumes much time. This paper proposes a pipelined design methodology which can improve the speed of crypto operations in ECB mode. Because the operations of the many rounds are concatenated in serial and executed concurrently, the overall computation time can be reduced significantly. The experimental result shows that the method can speed up the performance more than ten times.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.285-287
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• 1999

블록 암호알고리즘에 대한 기존의 연산 모드들(ECB 또는 CBC 등)은, 각 블록에 대하여 동일한 키로 암호화를 수행한다. 이것은 침입자가 한번의 암호 요청만을 수행하여 많은 수의 평문/암호문 쌍을 얻을 수 있게 함으로써 차분해독법 등의 공격에는 안전성을 제공하지 않는다. 본 논문에서는 블록 암호 알고리즘을 위한 새로운 모드를 제안하는데, 이 모드에서는 암호화되는 각각의 블록이 서로 다른 키로 암호화되도록 함으로써 블록의 개수가 많아짐에 따라 안전성 면에서 상당한 이득을 얻게 된다. 각 블록을 위한 서로 다른 키를 생성하는 것이 추가 연산을 필요로 하지만, 제안하는 모드를 DES에 적용한 TDK(a mode for DEA with unTraceable Dynamic Keys)의 수행 시간을 pentium과 sun sparc 상에서 측정해 본 결과 ECB 모드와 거의 유사함을 알 수 있었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.02a
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• pp.85-87
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• 2008

Kumar 등은 interlacing과 decomposition을 적용한 112-비트 블록 암호를 제안하였다. 본 논문에서는 이 블록 암호에 대한 첫 번째 분석 결과를 소개한다. 이 블록 암호를 구성하는 연산들은 모두 선형성만을 가지고 있다. 따라서 112개의 독립인 평문/암호문 쌍이 주어졌을 경우, 비밀키를 복구하지 않더라도 임의의 암호문을 복호화할 수 있다. 본 논문의 분석 결과를 통하여 이 블록 암호는 매우 취약함을 알 수 있다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.3
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• pp.439-445
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• 2012

Since an attacker can extract secret key of cryptographic device by occurring an error during encryption operation, the fault injection attack have become a serious threat in cryptographic system. In this paper, we show that an attacker can retrieve the 128-bits secret key in AES implementation adopted iterative statement for round operations using fault injection attack. To verify the feasibility of our attack, we implement the AES algorithm on ATmega128 microcontroller and try to inject a fault using laser beam. As a result, we can extract 128-bits secret key by obtaining just two pairs of correct and faulty ciphertexts.

• The Transactions of the Korea Information Processing Society
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• v.13 no.7
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• pp.291-298
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• 2024

Despite its wide application, cloud computing raises privacy leakage concerns because users should send their private data to the cloud. Homomorphic encryption (HE) can resolve the concerns by allowing cloud servers to compute on encrypted data without decryption. However, due to the huge computation overhead of HE, simply executing an entire cloud program with HE causes significant computation. Manually partitioning the program and applying HE only to the partitioned program for the cloud can reduce the computation overhead. However, the manual code partitioning and HE-transformation are time-consuming and error-prone. This work proposes a new homomorphic encryption enabled annotation-guided code partitioning compiler, called Heapa, for privacy preserving cloud computing. Heapa allows programmers to annotate a program about the code region for cloud computing. Then, Heapa analyzes the annotated program, makes a partition plan with a variable list that requires communication and encryption, and generates a homomorphic encryptionenabled partitioned programs. Moreover, Heapa provides not only two region-level partitioning annotations, but also two instruction-level annotations, thus enabling a fine-grained partitioning and achieving better performance. For six machine learning and deep learning applications, Heapa achieves a 3.61 times geomean performance speedup compared to the non-partitioned cloud computing scheme.

• Journal of Broadcast Engineering
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• v.18 no.5
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• pp.758-770
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• 2013

In a Broadcast Encryption System, a sender sends an encrypted message to a large set of receivers at once over an insecure channel and it enables only users in a target set to decrypt the message with their private keys. In 2005, Boneh et al. proposed a fully collusion-resistant public key broadcast encryption in which the ciphertext and the privatekey sizes are constant. In general, pairing-based broadcast encryption system is efficient in bandwidth and storing aspects than non-pairing based broadcast encryption system, however, it requires many computational costs that resource-constrained devices is not suit to be applied. In this paper, we propose a Broadcast Encryption scheme(called BEWD) that user can decrypt a ciphertext more efficiently. The scheme is based on Boneh et al.scheme. More precisely, it reduces receiver's computational costs by delegating pairing computation to a proxy server which computation is required to receiver in Boneh et al.scheme. Furthermore, the scheme enables a user to check if the proxy server compute correctly. We show that our scheme is secure against selective IND-RCCA adversaries under l-BDHE assumption.

• Journal of Industrial Convergence
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• v.17 no.1
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• pp.1-6
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• 2019

Various cryptographic technologies have been proposed from ancient times and are developing in various ways to ensure the confidentiality of information. Due to exponentially increasing computer power, the encryption key is gradually increasing for security. Technology are being developed; however, security is guaranteed only in a short period of time. With the advent of the 4th Industrial Revolution, encryption technology is required in various fields. Recently, encryption technology using homomorphic encryption has attracted attention. Security threats arise due to the exposure of keys and plain texts used in the decryption processing for the operation of encrypted information. The homomorphic encryption can compute the data of the cipher text and secure process the information without exposing the plain text. When using the homomorphic encryption in processing big data like stored personal information in various services, security threats can be avoided because there is no exposure to key usage and decrypted information.