• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.1
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• pp.87-100
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• 2020

Researches on Post-quantum blockchain, which is a synthesis of blockchain and post-quantum cryptography[1], are relatively unrevealed areas but have needs to be studied with the regard to the quantum computers. However there could be several fundamental problems, e.g. unsustainably large size of public key and signature, or too lengthy time for sign and verification, if any post-quantum cryptography is adopted to the existing blockchain to implement post-quantum blockchain. Thus, a new method was proposed in this paper that produces fixed length of references for massive signatures and corresponding public keys to enable relatively lightweight transactions. This paper proposed the mechanism that included a new transaction structure and protocols, and demonstrated a post-quantum blockchain that the proposed mechanism was adopted. Through this research, it could enhance compatibility of blockchain regarding post-quantum digital signature, possibly reducing weights of the whole blockchain.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.3
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• pp.533-544
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• 2021

Using Shor algorithm, factoring and discrete logarithm problem can be solved effectively. The public key cryptography, such as RSA and ECC, based on factoring and discrete logarithm problem can be broken in polynomial time using Shor algorithm. NIST has been conducting a PQC(Post Quantum Cryptography) standardization process to select quantum-resistant public key cryptography. The multivariate quadratic based signature scheme, which is one of the PQC candidates, is suitable for IoT devices with limited resources due to its short signature and fast sign and verify process. We analyzes classic attacks and quantum attacks for Rainbow which is the only multivatiate quadratic based signature scheme to be finalized up to the round 3. Also we compute the attack complexity for the round 3 Rainbow parameters, and analyzes the security level of Rainbow, one of the PQC standardization candidates.

• Journal of Internet Computing and Services
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• v.20 no.3
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• pp.25-31
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• 2019

Along with the recent advances in quantum computers, it is anticipated that cryptographic attacks using them will make it insecure to use existing public key algorithms such as RSA and ECC. Currently, a lot of researches are underway to replace them by devising PQC (Post Quantum Cryptography) schemes. In this paper, we propose a performance enhancement method for Lizard implementation which is one of NIST PQC standardization submission. The proposed method is able to improve the performance by 7 ~ 25% for its algorithms compared to the implementation in the submission through the techniques of various implementation aspects. This study hopes that Lizard will become more competitive as a candidate for PQC standardization.

• KIPS Transactions on Computer and Communication Systems
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• v.12 no.6
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• pp.181-188
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• 2023

Block cipher is not expected to be safe for quantum computer, as Grover's algorithm reduces the security strength by accelerating brute-force attacks on symmetric key ciphers. So it is necessary to check the post-quantum security strength by implementing quantum circuit for the target cipher. In this paper, we propose the optimal quantum circuit implementation result designed as a technique to minimize the use of quantum resources (qubits, quantum gates) for SIMECK lightweight cryptography, and explain the operation of each quantum circuit. The implemented SIMECK quantum circuit is used to check the estimation result of quantum resources and calculate the Grover attack cost. Finally, the post-quantum strength of SIMECK lightweight cryptography is evaluated. As a result of post-quantum security strength evaluation, all SIMECK family cipher failed to reach NIST security strength. Therefore, it is expected that the safety of SIMECK cipher is unclear when large-scale quantum computers appear. About this, it is judged that it would be appropriate to increase the block size, the number of rounds, and the key length to increase the security strength.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.5
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• pp.1089-1098
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• 2018

As the development of quantum computers becomes visible, the researches on post-quantum cryptography to alternate the present cryptography system have actively pursued. To substitute RSA and Elliptic Curve Cryptosystem, post-quantum cryptography must also consider side channel resistance in implementation. In this paper, we propose a side channel analysis on NTRU, based on the implementation made public in the NIST standardization. Unlike the previous analysis which exploits a thousands of traces, the proposed attack can recover the private key using a single power consumption trace. Our attack not only reduces the complexity of the attack but also gives more possibility to analyze a practical public key cryptosystem. Furthermore, we suggested the countermeasure against our attacks. Our countermeasure is much more efficient than existing implementation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.73-83
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• 2018

There has been increasing interest from NIST and other companies in studying post-quantum cryptography in order to resist against quantum computers. Multivariate polynomial based, code based, lattice based, hash based digital signature, and isogeny based cryptosystems are one of the main categories in post quantum cryptography. Among these categories, isogeny based cryptosystem is known to have shortest key length. In this paper, we implemented Supersingular Isogeny Diffie-Hellman (SIDH) protocol efficiently on low-end mobile device. Considering the device's specification, we select supersingular curve on 523 bit prime field, and generate efficient isogeny computation tree. Our implementation of SIDH module is targeted for 32bit environment.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.3
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• pp.481-496
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• 2021

It is imperative to migrate the current public key cryptosystem to a quantum-resistance system ahead of the realization of large-scale quantum computing technology. The National Institute of Standards and Technology, NIST, is promoting a public standardization project for Post-Quantum Cryptography(PQC) and also many research efforts have been conducted to apply PQC to TLS(Transport Layer Security) protocols, which are used for Internet communication security. In this paper, we propose a scenario in which a server and multi-clients share session keys on TLS by using the parallelized NTRU which is PQC in the key exchange process. In addition, we propose a method of accelerating NTRU using GPU and analyze its efficiency in an environment where a server needs to process large-scale data simultaneously.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.5
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• pp.709-719
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• 2023

Recently, Post-Quantum Cryptography (PQC), which is secure against attacks using quantum computers, has been actively studied. In 2022, the KpqC competition, a competition for domestic PQC standardization, was launched, and a total of 16 candidate algorithms were received, and the first round is underway. In this paper, we apply Alexander May's Meet-LWE attack to TiGER, a lattice-based key encapsulation mechanism that is a candidate for the first round of the KpqC competition, and analyze its concrete attack complexity. The computational results of applying the Meet-LWE attack to each of the proposed parameters of TiGER show that the proposed TiGER192 parameter, which targets 192-bit quantum security, actually achieves 170-bit classical security. In addition, we propose a parameter setting to increase the attack complexity against the Meet-LWE attack.

• ETRI Journal
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• v.45 no.6
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• pp.1090-1102
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• 2023

Authenticated multiple key agreement (AMKA) protocols provide participants with multiple session keys after one round of authentication. Many schemes use Diffie-Hellman or authenticated key agreement schemes that rely on hard integer factorizations that are vulnerable to quantum algorithms. Lattice cryptography provides quantum resistance to authenticated key agreement protocols, but the certificate always incurs excessive public key infrastructure management overhead. Thus, a lightweight lattice-based secure system is needed that removes this overhead. To answer this need, we provide a two-party lattice- and identity-based AMKA scheme based on bilateral short integer or computational bilateral inhomogeneous small integer solutions, and we provide a security proof based on the random oracle model. Compared with existing AMKA protocols, our new protocol has higher efficiency and stronger security.

• TTA Journal
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• s.177
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• pp.107-109
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• 2018