We propose a code-based signature scheme in the Lee metric.
The main features of the submission are:

  • Alternative Metric: The already standardized signature schemes are either based on structured lattices or on hash functions. While classical code-based cryptography considers vector spaces endowed with the Hamming metric, other metrics have attracted attention in the context of cryptography, e.g., the rank metric. This work marks the first Lee-metric-based cryptographic primitive.
  • Small Signatures: FuLeeca achieves small communication costs, i.e., small signature size plus public key size. This is an important quantity for certificate chains. When comparing with the to be standarized schemes, the combined size of signature and public key of FuLeeca is slightly larger than the one of Falcon but smaller than the ones of Dilithium and SPHINCS+. For NIST security level I, we achieve a public key size of 1318 bytes and a signature size of 1100 bytes. The public key size is basically the same is in Dilithium (for level II), but larger than the one for the hash-based scheme SPHINCS+. However, SPHINCS+’s signature size is significantly larger than the one of FuLeeca. In fact, the signature size of FuLeeca is only 14% of the signature size of SPHINCS+ and about 50% smaller than for Dilithium.

Project Team

  • Stefan Ritterhoff
  • Sebastian Bitzer
  • Patrick Karl
  • Georg Maringer
  • Thomas Schamberger
  • Jonas Schupp
  • Georg Sigl
  • Antonia Wachter-Zeh
  • Violetta Weger