Paper 2026/493

The SQInstructor: a guide to SQIsign and the Deuring Correspondence with level structures

Giacomo Borin, IBM Research - Zurich, University of Zurich
Luca De Feo, IBM Research - Zurich
Guido Maria Lido, University of Rome Tor Vergata
Sina Schaeffler, IBM Research - Zurich, ETH Zurich
Abstract

We explore the use of level structures to generalize the SQIsign signature scheme. We give a general framework where, given the public key and the commitment, the challenge is to exhibit an isogeny between them with an additional requirement, namely to map a chosen level structure to nother. We then instantiate the framework using 1-dimensional and 2-dimensional isogenies. In doing that we provide a new explicit Deuring correspondence for supersingular elliptic curves with level structures and solve new constrained norm equations.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Preprint.
Keywords
isogeniespost-quantum cryptographysupersingular elliptic cuvesdigital signatureslevel structures
Contact author(s)
sqisign @ gbor in
iacr-papers @ defeo lu
guidomaria lido @ gmail com
sschaeffle @ ethz ch
History
2026-03-11: revised
2026-03-10: received
See all versions
Short URL
https://ia.cr/2026/493
License
Creative Commons Attribution-ShareAlike
CC BY-SA

BibTeX

@misc{cryptoeprint:2026/493,
      author = {Giacomo Borin and Luca De Feo and Guido Maria Lido and Sina Schaeffler},
      title = {The {SQInstructor}: a guide to {SQIsign} and the Deuring Correspondence with level structures},
      howpublished = {Cryptology {ePrint} Archive, Paper 2026/493},
      year = {2026},
      url = {https://eprint.iacr.org/2026/493}
}
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