Paper 2023/426

A Tightly Secure Identity-based Signature Scheme from Isogenies

Hyungrok Jo, Yokohama National University
Shingo Sato, Yokohama National University
Junji Shikata, Yokohama National University

We present a tightly secure identity-based signature (IBS) scheme based on the supersingular isogeny problems. Although Shaw and Dutta proposed an isogeny-based IBS scheme with provable security, the security reduction is non-tight. For an IBS scheme with concrete security, the tightness of its security reduction affects the key size and signature size. Hence, it is reasonable to focus on a tight security proof for an isogeny-based IBS scheme. In this paper, we propose an isogeny-based IBS scheme based on the lossy CSI-FiSh signature scheme and give a tight security reduction for this scheme. While the existing isogeny-based IBS has the square-root advantage loss in the security proof, the security proof for our IBS scheme avoids such advantage loss, due to the properties of lossy CSI-FiSh.

Available format(s)
Public-key cryptography
Publication info
Identity-based signaturesIsogeny-based cryptographyPost-quantum cryptography
Contact author(s)
jo-hyungrok-xz @ ynu ac jp
sato-shingo-zk @ ynu ac jp
shikata-junji-rb @ ynu ac jp
2023-03-24: approved
2023-03-24: received
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      author = {Hyungrok Jo and Shingo Sato and Junji Shikata},
      title = {A Tightly Secure Identity-based Signature Scheme from Isogenies},
      howpublished = {Cryptology ePrint Archive, Paper 2023/426},
      year = {2023},
      note = {\url{}},
      url = {}
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