I am Jincheol Ha, an assistant professor at School of AI & Software, Soongsil University. My research interest includes homomorphic encryption schemes such as CKKS and TFHE, the design of symmetric-key primitives for privacy-enhancing technologies (such as homomorphic encryption and zero-knowledge proofs), and the cryptanalysis of symmetric ciphers.

I was a research engineer at CryptoLab Inc., Korea. My research at CryptoLab focused on private iris recognition using the CKKS homomorphic encryption scheme.

I received my B.S. in Mathematical Sciences and Computer Science (double major) from KAIST, and my M.S. and Ph.D. degrees from the Graduate School of Information Security (GSIS) at KAIST, advised by Prof. Jooyoung Lee. During my doctoral studies, I worked on improving the practical use of TFHE by proposing a TFHE-friendly cipher named FRAST, and enhancing methods for the homomorphic evaluation in TFHE. My thesis is titled “Practical and Efficient Methods to Use the TFHE Scheme”. I also participated in projects designing symmetric-key primitives integrated with another advanced cryptographic protocols such as MPC-in-the-Head (AIMer signature) and zero-knowledge proofs.

Publications

Authors are listed in alphabetical order by last name, unless an asterisk(*) is indicated. Two asterisks imply the co-first authors.

• Refined TFHE Leveled Homomorphic Evaluation and Its Application
  R. Wang(*), J. Ha(*), X. Shen, X. Lu, C. Chen, K. Wang, and J. Lee.
  The 32nd ACM Conference on Computer and Communications Security (CCS 2025).
• Polocolo: A ZK-Friendly Hash Function Based on S-boxes Using Power Residues
  J. Ha, S. Hwang, J. Lee, S. Park, and M. Son.
  The 44th Annual International Conference on the Theory and Applications of Cryptographic Techniques (EUROCRYPT 2025).
• FRAST: TFHE-Friendly Cipher Based on Random S-boxes
  M. Cho, W. Chung, J. Ha, J. Lee, E. Oh, and M. Son.
  Transactions on Symmetric Cryptology (ToSC), 2024, Issue 3.
• Efficacy and Mitigation of the Cryptanalysis on AIM
  S. Kim(*), J. Ha, M. Son, and B. Lee.
  The 5th NIST PQC Standardization Conference, 2024.
• AIM: Symmetric Primitive for Shorter Signatures with Stronger Security
  S. Kim(*), J. Ha(*), M. Son, B. Lee, S. Lee, J. Kwon, J. Cho, H. Yoon, and J. Lee.
  The 30th ACM Conference on Computer and Communications Security (CCS 2023).
• Rubato: Noisy Ciphers for Approximate Homomorphic Encryption
  J. Ha, S. Kim, B. Lee, J. Lee, and M. Son.
  The 41st Annual International Conference on the Theory and Applications of Crypto- graphic Techniques (EUROCRYPT 2022).
• Transciphering Framework for Approximate Homomorphic Encryption
  J. Cho, J. Ha, S. Kim, B. Lee, J. Lee, J. Lee, D. Moon, and H. Yoon.
  International Conference on the Theory and Application of Cryptology and Information Security (ASIACRYPT 2021).
• Masta: An HE-friendly Ciphers Using Modular Arithmetic
  J. Ha(*), S. Kim, W. Choi, J. Lee, D. Moon, H. Yoon, and J. Cho.
  IEEEAccess 2020.

Preprint

• Private Iris Recognition with High-Performance FHE
  J. Ha(*), G. Hanrot, T. Noh, JH. Cheon, JW. Kim, and D. Stehlé.
  arXiv:2601.17561

Talks

• Refined TFHE Leveled Homomorphic Evaluation and Its Application
  (Invited) 2025 KMS Annual Meeting, Oct. 2025, Seoul, Korea
  2025 ACM CCS, Oct. 2025, Taipei, Taiwan
• FRAST: TFHE-Friendly Cipher Based on Random S-boxes
  The 31st Fast Software Encryption Conference, Mar. 2025, Rome, Italy
  2023 KMS Annual Meeting, Oct. 2023, Seoul, Korea
  2023 KSIAM Spring Conference, May. 2023, Pyeong Chang, Korea
• AIMer
  “Aimer”, 2024 KpqC Winter Camp, Feb. 2024, Seoul, Korea
  “AIM에 대한 분석 및 대응”, KpqC 연구단 7차 워크숍, Nov. 2023, Seoul, Korea
  “Aimer: ZKP-based Digital Signature”, 2023 KpqC Winter Camp, Feb. 2023, Seoul, Korea
• On the Number of Linearly Independent Boolean Equations of Power Mapping Based S-boxes
  (Invited) KIAS, Nov. 2022, Online
• Masta: An HE-friendly Cipher Using Modular Arithmetic
  2020 KMS Fall Meeting, Oct. 2020, Online