https://scholar.dgist.ac.kr/handle/20.500.11750/46475 2026-04-04T13:37:08Z https://scholar.dgist.ac.kr/handle/20.500.11750/59965 Title: Overlapped Bootstrapping for FHEW/TFHE and Its Application to SHA3 Author(s): Hong, Deokhwa; Choi, Youngjin; Lee, Yongwoo; Kim, Young-Sik Abstract: Homomorphic Encryption (HE) enables operations on encrypted data without requiring decryption, thus allowing secure handling of confidential data within smart contracts. Among the known HE schemes, FHEW and TFHE are particularly notable for use in smart contracts due to their lightweight nature and support for arbitrary logical gates. In contrast, other HE schemes often require several gigabytes of keys and are limited to supporting only addition and multiplication. As a result, many studies have been conducted on implementing smart contract functionalities over HE, broadening the potential applications of blockchain technology. However, a significant drawback of the FHEW/TFHE schemes is the need for bootstrapping after the execution of each binary gate. While bootstrapping reduces noise in the ciphertext, it also becomes a performance bottleneck due to its computational complexity. In this work, we propose an efficient new bootstrapping method for FHEW/TFHE that takes advantage of the flexible scaling factors of encrypted data. The proposed method is particularly beneficial in circuits with consecutive XOR gates. Moreover, we implement Keccak using FHEW/TFHE, as it is one of the most important functions in smart contracts. Our experimental results demonstrate that the proposed method reduces the runtime of Keccak over HE by 42%. Additionally, the proposed method does not require additional keys or parameter sets from the key-generating party and can be adopted by the computing party without the need for any extra information. © International Financial Cryptography Association 2026. 2025-04-14T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59865 Title: CKKS 동형암호를 이용한 ARX 연산 효율화 및 LEA 블록암호 키 마이그레이션 프레임워크 Author(s): 이재연; 정세훈; 김영식; 조승현 https://scholar.dgist.ac.kr/handle/20.500.11750/59854 Title: 블록체인 기반 실시간 자율주행 차량 데이터 무결성 보장 기술 시뮬레이션 프로그램 v1.0 Author(s): 임우상; 전재호; 서유진; 김영식; 김광식 https://scholar.dgist.ac.kr/handle/20.500.11750/59143 Title: Post-Quantum Cryptography Migration on V2X Certificate using KpqC Algorithms Author(s): Seo, Yujin; Kim, Young-Sik Abstract: Connected vehicles utilizing Vehicle-to-Everything (V2X) communication enhance road safety and transportation efficiency, supporting cooperative autonomous driving through real-time interactions. However, increased connectivity raises cyber-attack risks, endangering driver and pedestrian safety. This highlights the urgent need to integrate Post-Quantum Cryptography (PQC) into vehicular communications [6]. In this paper, we implement the Korean PQC digital signature algorithm HAETAE for V2X environments and compare its performance with the NIST PQC signature scheme, ML-DSA which is derived from CRYSTALS-DILITHIUM, and traditional signatures, RSA, and ECC under TLS 1.3 environments. Results indicate that PQC algorithms introduce substantial overhead, whereas traditional algorithms produce smaller certificates. Specifically, HAETAE provides more efficient certificates than ML-DSA [3], minimizing latency impacts in TLS operations. These findings inform the critical balance between enhanced security and certificate size, guiding future post-quantum TLS designs. © 2025 Elsevier B.V., All rights reserved. 2025-07-07T15:00:00Z