[Resource Topic] 2023/426: A Tightly Secure Identity-based Signature Scheme from Isogenies

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A Tightly Secure Identity-based Signature Scheme from Isogenies

Authors: Hyungrok Jo, Shingo Sato, Junji Shikata


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.

ePrint: https://eprint.iacr.org/2023/426

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