名古屋大学 · 情報科学
Akinori Hosoyamada教授の研究室は、量子コンピュータ時代における暗号方式の安全性を解明する分野に注力しています。特に、従来の古典的セキュリティが保証される対称暗号方式が、量子攻撃（特に量子重ね合わせ攻撃）によって多項式時間で破壊される可能性を解明しており、Even-Mansour暗号やCBC-MAC、Feistel構造などに対する量子攻撃の新手法を提案しています。また、量子環境下でも安全な認証付き暗号やトゥイクルブロック暗号の設計原理の限界についても理論的・構成的アプローチを展開しています。
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It has been said that security of symmetric key schemes is not so much affected by quantum computers, compared to public key schemes. However, recent works revealed that, in some specific situations, symmetric key schemes are also broken in polynomial time by adversaries with quantum computers. These works contain a quantum distinguishing attack on 3-round Feistel ciphers and a quantum key recovery attack on the Even-Mansour cipher by Kuwakado and Morii, in addition to the quantum forgery attack
Recent results on quantum cryptanalysis show that some symmetric key schemes can be broken in polynomial time even if they are proven to be secure in the classical setting. Liskov, Rivest, and Wagner showed that secure tweakable block ciphers can be constructed from secure block ciphers in the classical setting. However, Kaplan et al. showed that their scheme can be broken by polynomial time quantum superposition attacks, even if underlying block ciphers are quantum-secure. Since then, it remain
Rocca is an authenticated encryption with associated data scheme for beyond 5G/6G systems. It was proposed at FSE 2022/ToSC 2021(2), and the designers make a security claim of achieving 256-bit security against key-recovery and distinguishing attacks, and 128-bit security against forgery attacks (the security claim regarding distinguishing attacks was subsequently weakened in the full version in ePrint 2022/116). A notable aspect of the claim is the gap between the privacy and authenticity secur
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