Study on developing lattice decoding algorithms and cryptanalysis to lattice-based cryptography

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K23322
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 1001:Information science, computer engineering, and related fields
• Research Institution: Osaka University (2021); Japan Advanced Institute of Science and Technology (2020)
• Principal Investigator: Wang Yuntao 大阪大学, 工学研究科, 講師 (00880791)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: 格子暗号 / 解読アルゴリズム / 公開鍵暗号 / 安全性解析

Outline of Final Research Achievements

In this research project, we focused on security evaluation for the practical use of post-quantum cryptography (PQC). In particular, we developed and improved several decoding algorithms for the approximation of shortest vector problem (SVP), which is the security evidence for lattice-based cryptography, one of the most promising candidates for PQC. We achieved a world record of 158 dimensions in the SVP decoding challenge organized by the Technical University of Darmstadt, Germany. Furthermore, we also improved ENUM (a lattice search algorithm) and Tuple Sieve (a sieve method) to reduce their computational and memory costs, respectively. In addition, we evaluated the security of random number reuse attacks against the lattice-based CRYSTALS-KYBER and SABER. As a result, we obtained a 100% success rate while the number of queries was less than 6.

Free Research Field

耐量子計算機暗号

Academic Significance and Societal Importance of the Research Achievements

本研究課題では，次世代暗号の有力候補である格子暗号の解読アルゴリズムを改良し，スーパコンピュータで大規模解読実験を行い，世界記録を達成した．更に，格子暗号に対する攻撃法を考察することにより，実応用ではよく用いられる「乱数再利用」の安全性評価ができた．本研究課題により，耐量子計算機暗号への解読効率を向上させ，それに応じて頑丈な暗号パラメータの選出に参考できることと，乱数再利用の危機性を示したため学術的かつ実用的な貢献は大きいと考える．