• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.20 no.6
• /
• pp.59-65
• /
• 2010

Since an attacker can occur an error in cryptographic device during encryption process and extract secret key, the fault injection attack has become a serious threat in chip security. In this paper, we show that an attacker can retrieve the 128-bits secret key using fault injection attack on the for statement of final round key addition in AES implementation. To verify possibility of our proposal, we implement the AES system on ATmega128 microcontroller and try to inject a fault using laser beam. As a result, we can extract 128-bits secret key through just one success of fault injection.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2012.11a
• /
• pp.1009-1012
• /
• 2012

프록시 재암호화 기법이란 위임하는 사람의 공개키로 암호화된 암호문을 신뢰기관의 도움 없이 위임 받는 사람의 개인키로 복호화할 수 있도록 변환하는 기법이다. 이후 특정 조건을 만족하는 사용자만 복호화할 수 있도록 하기 위해 조건부 프록시 재암호화 기법이 제안되었다. 2009 년 Weng 등에 의해 조건부 프록시 재암호화 기법이 제안된 이래 조건에 대해 Boolean 연산자를 모두 지원하는 방법은 아직까지 Open Problem 으로 남아있다. 현재 AND 연산에 대해서는 기존의 기법을 확장하여 지원할 수 있으나 OR, NOT 등에 대해서는 아직 제안되지 않았다. 본 논문에서는 기존의 기법을 확장하여 AND 연산과 함께 OR 연산도 지원할 수 있는 조건부 프록시 재암호화 기법을 제안한다

• Proceedings of the Korea Information Processing Society Conference
• /
• 2010.04a
• /
• pp.826-827
• /
• 2010

통신이 발전함에 따라 웹하드와 같은 원격 데이터 저장 서버에 PC에 사용되던 자료를 저장하여 언제 어디서든 접근할 수 있는 서비스가 발전하게 되었다. 하지만 데이터를 저장하는 서버의 신뢰 문재가 발생하게 되었고, 이를 해결하기위해 서버에 저장되는 데이터의 암호화 및 이를 검색할 수 있는 기술이 필요하게 되었다. 하지만 기존의 대칭키 검색 가능 암호 시스템은 결합 키워드 검색 시 연산의 효율성이 떨어지는 문제점이 존재한다. 따라서 본 논문은 블룸필터를 사용하여 효율적인 대칭키 기반 결합키워드 검색 가능 암호 시스템을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2011.04a
• /
• pp.869-870
• /
• 2011

통신이 발달로 인터넷 망을 이용해 고용량의 데이터를 빠르게 주고받을 수 있게 되었으며, 이로 인하여 데이터를 원격 저장소에 저장하여 언제 어디서든 빠르게 접근할 수 있는 서비스가 발전하게 되었다. 하지만 데이터를 저장하는 서버의 보안 및 서버관리자의 신뢰 문재가 발생하게 되었고, 이를 해결하기위해 서버에 저장되는 데이터의 암호화 및 이를 검색할 수 있는 기술이 필요하게 되었다. 기존의 검색 가능 암호의 경우 이메일 서비스를 기반으로 구성이 되어 하나의 데이터에 많은 키워드를 저장하게 되는 원격 저장소 서비스에 적용하기 어렵다. 또한 필드 기반 검색기능을 제공해 검색이 유연하지 않고 결합 키워드 검색 시 연산의 효율성이 떨어지는 문제점이 존재한다. 따라서 본 논문은 블룸필터를 사용하여 대량의 키워드를 효율적으로 저장 및 검색 할 수 있으며 필드 프리한 결합키워드 검색을 지원하는 공개키 검색 가능 암호 시스템을 제안한다.

• Journal of the Korea Society for Simulation
• /
• v.24 no.4
• /
• pp.153-161
• /
• 2015

We propose a privacy-preserving location-based service (LBS) which supports top-k search service. The previous schemes hurt the privacy of either the user and the location of the objects because they are sent to the LBS server in a plaintext form. In the proposed method, by encrypting them with the fully-homomorphic encryption, we achieved the top-k search is possible while the information on them is not given to the LBS server. We performed a simulation on the proposed scheme with 16 locations where k is 3. The required time is 270 hours in a conventional desktop machine, which seems infeasible to be used in practice. However, as the progress of the hardware, the performance will be improved.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.30 no.5
• /
• pp.781-793
• /
• 2020

In this paper, we propose a new RLWE-based scheme named μ-Hope that exploits Error Correcting Code(ECC) on NewHope. The previous parameters of NewHope uses 12289 as a prime modulus, and the size of the public key, private key, and ciphertext is 928-byte, 1888-byte, and 1120-byte respectively, which can be said to be larger than other RLWE based algorithms. In this paper, we propose μ-Hope, which changes modulus 12289 to 769 to reduce the size of the public key, private key, and ciphertext. Also, we adopts XE1 as an Error Correcting Code(ECC) to solve the increased decryption failure rate caused by using a small prime modulus. As a result, the size of the public key, private key, and ciphertext decreased by 38%, 37%, and 37% respectively. As the computational efficiency caused by using a small prime modulus exceeds the performance degradation by exploiting ECC, this result in 25% performance improvement for a single key exchange.

• Convergence Security Journal
• /
• v.14 no.2
• /
• pp.51-56
• /
• 2014

Be expressed in network-centric warfare, mainly battlefield environment of the future. The purpose of the system for the war of the future, is to recognize the enemy before the enemy, and rapid decision-making, to hit accurately. For this reason, it is during the construction of the integrated system of C4ISR+PGM. In such an integrated system, it is necessary to further enhance the security aspects of the information. In particular, strengthening of security leads to a decrease of efficiency. Therefore, security and efficiency should be considered together. In this study, we provide a homomorphic encryption system that can be safely managed information environment on the battlefield of the future. The proposed method uses encryption technology of homomorphic that can be the arithmetic operations on encrypted state. It has changed from the state of the encryption. Therefore, the attacker can not know a decent information.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.23 no.5
• /
• pp.859-865
• /
• 2013

Esmbedded devices such as smart cards and electronic passports highly demand security of sensitive data. So, the secure implementation of the cryptographic system against various side-channel attacks are becoming more important. In particular, the fault injection attack is one of the threats to the cryptosystem and can destroy the whole system only with single pair of the plain and cipher texts. Therefore, the implementors must consider seriously the attack. Several techniques for preventing fault injection attacks were introduced to a variety of the cryptosystem, But the countermeasures are still inefficient to be applied to the classical RSA cryptosystem. This paper introduces an efficient countermeasure against the fault injection attack for the classical RSA cryptosystem, which is based on the famous Fermat's theorem. The proposed countermeasure has the advantage that it has less computational overhead, compared with the previous countermeasures.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.1
• /
• pp.57-70
• /
• 2014

Inner product encryption (IPE) scheme is a cryptographic primitive that provides fine grained relations between secret keys and ciphertexts. This paper proposes a new IPE scheme which achieves fully attribute hiding security. Our IPE scheme is based on bilinear groups of a composite order. We prove the fully attribute hiding security of our IPE by using dual encryption system framework. In performance analysis, we compare the computation cost and memory requirement of our proposed IPE to other existing IPE schemes.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.28 no.5
• /
• pp.1071-1078
• /
• 2018

Recently, a family of lightweight block ciphers CHAM that has effective performance on resource-constrained devices is proposed. The CHAM uses a stateless-on-the-fly key schedule method which can reduce the key storage areas. Furthermore, the core design of CHAM is based on ARX(Addition, Rotation and XOR) operations which can enhance the computational performance. Nevertheless, we point out that the CHAM algorithm may be vulnerable to the fault injection attack which can reveal 4 round keys and derive the secret key from them. As a simulation result, the proposed fault injection attack can extract the secret key of CHAM-128/128 block cipher using about 24 correct-faulty cipher text pairs.